Fast wave current drive on DIII-D

International Nuclear Information System (INIS)

deGrassie, J.S.; Petty, C.C.; Pinsker, R.I.; Forest, C.B.; Ikezi, H.; Prater, R.; Baity, F.W.; Callis, R.W.; Cary, W.P.; Chiu, S.C.; Doyle, E.J.; Ferguson, S.W.; Hoffman, D.J.; Jaeger, E.F.; Kim, K.W.; Lee, J.H.; Lin-Liu, Y.R.; Murakami, M.; ONeill, R.C.; Porkolab, M.; Rhodes, T.L.; Swain, D.W.

1996-01-01

The physics of electron heating and current drive with the fast magnetosonic wave has been demonstrated on DIII-D, in reasonable agreement with theoretical modeling. A recently completed upgrade to the fast wave capability should allow full noninductive current drive in steady state advanced confinement discharges and provide some current density profile control for the Advanced Tokamak Program. DIII-D now has three four-strap fast wave antennas and three transmitters, each with nominally 2 MW of generator power. Extensive experiments have been conducted with the first system, at 60 MHz, while the two newer systems have come into operation within the past year. The newer systems are configured for 60 to 120 MHz. The measured FWCD efficiency is found to increase linearly with electron temperature as γ=0.4x10 18 T e0 (keV) [A/m 2 W], measured up to central electron temperature over 5 keV. A newly developed technique for determining the internal noninductive current density profile gives efficiencies in agreement with this scaling and profiles consistent with theoretical predictions. Full noninductive current drive at 170 kA was achieved in a discharge prepared by rampdown of the Ohmic current. Modulation of microwave reflectometry signals at the fast wave frequency is being used to investigate fast wave propagation and damping. Additionally, rf pick-up probes on the internal boundary of the vessel provide a comparison with ray tracing codes, with clear evidence for a toroidally directed wave with antenna phasing set for current drive. copyright 1996 American Institute of Physics

The high current, fast, 100ns, Linear Transformer Driver (LTD) developmental project at Sandia National Laboratories

International Nuclear Information System (INIS)

Ward, Kevin S.; Long, Finis W.; Sinebryukhov, Vadim A.; Kim, Alexandre A.; 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

2010-01-01

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.

Fast wave current drive on ITER in the presence of energetic alphas

International Nuclear Information System (INIS)

Mau, T.K.

1989-01-01

The impact of energetic alpha particle wave absorption on the range of frequencies for efficient fast wave current drive in an ITER-like fusion reactor core is investigated. The energetic alpha damping decrement is calculated, using an exact slowing down distribution function, and compared to electron and fuel ion damping over a wide range of frequencies. A combination of strong alpha damping and edge electron absorption in the higher ion harmonic regime limits efficient core fast wave current drive to the lower harmonics (1=2.3). However, high frequency fast waves may be employed to generate current in the outer plasma region. 11 refs., 7 figs

Intermittent fasting and cardiovascular disease: current evidence and unresolved questions.

Science.gov (United States)

Tinsley, Grant M; Horne, Benjamin D

2018-01-01

Intermittent fasting has produced a variety of beneficial health effects in animal models, although high-quality research in humans has been limited. This special report examines current evidences for intermittent fasting in humans, discusses issues that require further examination, and recommends new research that can improve the knowledge base in this emerging research area. While potentially useful for health improvement, intermittent fasting requires further study prior to widespread implementation for health purposes. Randomized, longer-term studies are needed to determine whether using intermittent fasting as a lifestyle rather than a diet is feasible and beneficial for the health of some members of the human population.

Current feedback operational amplifiers as fast charge sensitive preamplifiers for photomultiplier read out

Energy Technology Data Exchange (ETDEWEB)

Giachero, A; Gotti, C; Maino, M; Pessina, G, E-mail: claudio.gotti@mib.infn.it [INFN - Sezione di Milano-Bicocca, I-20126, Milano (Italy)

2011-05-01

Fast charge sensitive preamplifiers were built using commercial current feedback operational amplifiers for fast read out of charge pulses from a photomultiplier tube. Current feedback opamps prove to be particularly well suited for this application where the charge from the detector is large, of the order of one million electrons, and high timing resolution is required. A proper circuit arrangement allows very fast signals, with rise times down to one nanosecond, while keeping the amplifier stable. After a review of current feedback circuit topology and stability constraints, we provide a 'recipe' to build stable and very fast charge sensitive preamplifiers from any current feedback opamp by adding just a few external components. The noise performance of the circuit topology has been evaluated and is reported in terms of equivalent noise charge.

Current measurement method for characterization of fast switching power semiconductors with Silicon Steel Current Transformer

DEFF Research Database (Denmark)

Li, Helong; Beczkowski, Szymon; Munk-Nielsen, Stig

2015-01-01

This paper proposes a novel current measurement method with Silicon Steel Current Transformer (SSCT) for the characterization of fast switching power semiconductors. First, the existing current sensors for characterization of fast switching power semiconductors are experimentally evaluated...

Two dimensional code for modeling of high ione cyclotron harmonic fast wave heating and current drive

International Nuclear Information System (INIS)

Grekov, D.; Kasilov, S.; Kernbichler, W.

2016-01-01

A two dimensional numerical code for computation of the electromagnetic field of a fast magnetosonic wave in a tokamak at high harmonics of the ion cyclotron frequency has been developed. The code computes the finite difference solution of Maxwell equations for separate toroidal harmonics making use of the toroidal symmetry of tokamak plasmas. The proper boundary conditions are prescribed at the realistic tokamak vessel. The currents in the RF antenna are specified externally and then used in Ampere law. The main poloidal tokamak magnetic field and the ''kinetic'' part of the dielectric permeability tensor are treated iteratively. The code has been verified against known analytical solutions and first calculations of current drive in the spherical torus are presented.

Fast wave current drive in neutral beam heated plasmas on DIII-D

International Nuclear Information System (INIS)

Petty, C.C.; Forest, C.B.; Pinsker, R.I.

1997-04-01

The physics of non-inductive current drive and current profile control using the fast magnetosonic wave has been demonstrated on the DIII-D tokamak. In non-sawtoothing discharges formed by neutral beam injection (NBI), the radial profile of the fast wave current drive (FWCD) was determined by the response of the loop voltage profile to co, counter, and symmetric antenna phasings, and was found to be in good agreement with theoretical models. The application of counter FWCD increased the magnetic shear reversal of the plasma and delayed the onset of sawteeth, compared to co FWCD. The partial absorption of fast waves by energetic beam ions at high harmonics of the ion cyclotron frequency was also evident from a build up of fast particle pressure near the magnetic axis and a correlated increase in the neutron rate. The anomalous fast particle pressure and neutron rate increased with increasing NBI power and peaked when a harmonic of the deuterium cyclotron frequency passed through the center of the plasma. The experimental FWCD efficiency was highest at 2 T where the interaction between the fast waves and the beam ions was weakest; as the magnetic field strength was lowered, the FWCD efficiency decreased to approximately half of the maximum theoretical value

Technology of fast-wave current drive antennas

International Nuclear Information System (INIS)

Hoffman, D.J.; Baity, F.W.; Goulding, R.H.; Haste, G.R.; Ryan, P.M.; Taylor, D.J.; Swain, D.W.; Mayberry, M.J.; Yugo, J.J.

1989-01-01

The design of fast-wave current drive (FWCD) antennas combines the usual antenna considerations (e.g., the plasma/antenna interface, disruptions, high currents and voltages, and thermal loads) with new requirements for spectral shaping and phase control. The internal configuration of the antenna array has a profound effect on the spectrum and the ability to control phasing. This paper elaborates on these considerations, as epitomized by a proof-of-principle (POP) experiment designed for the DIII-D tokamak. The extension of FWCD for machines such as the International Thermonuclear Engineering Reactor (ITER) will require combining ideas implemented in the POP experiment with reactor-relevant antenna concepts, such as the folded waveguide. 6 refs., 8 figs

Fast-slow asymptotics for a Markov chain model of fast sodium current

Science.gov (United States)

Starý, Tomáš; Biktashev, Vadim N.

2017-09-01

We explore the feasibility of using fast-slow asymptotics to eliminate the computational stiffness of discrete-state, continuous-time deterministic Markov chain models of ionic channels underlying cardiac excitability. We focus on a Markov chain model of fast sodium current, and investigate its asymptotic behaviour with respect to small parameters identified in different ways.

Hamiltonian analysis of fast wave current drive in tokamak plasmas

Energy Technology Data Exchange (ETDEWEB)

Becoulet, A; Fraboulet, D; Giruzzi, G; Moreau, D; Saoutic, B [Association Euratom-CEA, Centre d` Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Chinardet, J [CISI Ingenierie, Centre d` Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France)

1993-12-01

The Hamiltonian formalism is used to analyze the direct resonant interaction between the fast magnetosonic wave and the electrons in a tokamak plasma. The intrinsic stochasticity of the electron phase space trajectories is derived, and together with extrinsic de-correlation processes, assesses the validity of the quasilinear approximation for the kinetic studies of fast wave current drive (FWCD). A full-wave resolution of the Maxwell-Vlasov set of equations provides the exact pattern of the wave fields in a complete tokamak geometry, for a realistic antenna spectrum. The local quasilinear diffusion tensor is derived from the wave fields, and is used for a computation of the driven current and deposited power profiles, the current drive efficiency, including possible non-linear effects in the kinetic equation. Several applications of FWCD on existing and future machines are given, as well as results concerning combination of FWCD with other non inductive current drive methods. An analytical expression for the current drive efficiency is given in the high single-pass absorption regimes. (authors). 20 figs., 1 tab., 26 refs.

Hamiltonian analysis of fast wave current drive in tokamak plasmas

International Nuclear Information System (INIS)

Becoulet, A.; Fraboulet, D.; Giruzzi, G.; Moreau, D.; Saoutic, B.

1993-12-01

The Hamiltonian formalism is used to analyze the direct resonant interaction between the fast magnetosonic wave and the electrons in a tokamak plasma. The intrinsic stochasticity of the electron phase space trajectories is derived, and together with extrinsic de-correlation processes, assesses the validity of the quasilinear approximation for the kinetic studies of fast wave current drive (FWCD). A full-wave resolution of the Maxwell-Vlasov set of equations provides the exact pattern of the wave fields in a complete tokamak geometry, for a realistic antenna spectrum. The local quasilinear diffusion tensor is derived from the wave fields, and is used for a computation of the driven current and deposited power profiles, the current drive efficiency, including possible non-linear effects in the kinetic equation. Several applications of FWCD on existing and future machines are given, as well as results concerning combination of FWCD with other non inductive current drive methods. An analytical expression for the current drive efficiency is given in the high single-pass absorption regimes. (authors). 20 figs., 1 tab., 26 refs

FWCD (fast wave current drive) and ECCD (electron cyclotron current drive) experiments on DIII-D

International Nuclear Information System (INIS)

Prater, R.; Austin, M.; Baity, F.W.

1994-01-01

Fast wave current drive and electron cyclotron current drive experiments have been performed on the DIII-D tokamak as part of the advanced tokamak program. The goal of this program is to develop techniques for controlling the profile of the current density in order to access regimes of improved confinement and stability. The experiments on fast wave current drive used a four strap antenna with 90deg phasing between straps. A decoupler was used to help maintain the phasing, and feedback control of the plasma position was used to keep the resistive loading constant. RF pickup loops demonstrate that the directivity of the antenna is as expected. Plasma currents up to 0.18 MA were driven by 1.5 MW of fast wave power. Electron cyclotron current drive experiments at 60 GHz have shown 0.1 MA of plasma current driven by 1 MW of power. New fast wave and electron cyclotron heating systems are in development for DIII-D, so that the goals of the advanced tokamak program can be carried out. (author)

LASL high-current proton storage rings

International Nuclear Information System (INIS)

Lawrence, G.P.; Cooper, R.K.; Hudgings, D.W.; Spalek, G.; Jason, A.J.; Higgins, E.F.; Gillis, R.E.

1980-01-01

The Proton Storage Ring at LAMPF is a high-current accumulator designed to convert long 800-MeV linac pulses into very short high-intensity proton bunches ideally suited to driving a pulsed polyenergetic neutron source. The Ring, authorized for construction at $19 million, will operate in a short-bunch high-frequency mode for fast neutron physics and a long-bunch low-frequency mode for thermal neutron-scattering programs. Unique features of the project include charge-changing injection with initial conversion from H - to H 0 , a high repetition rate fast-risetime extraction kicker, and high-frequency and first-harmonic bunching system

Bootstrap current of fast ions in neutral beam injection heating

International Nuclear Information System (INIS)

Huang Qianhong; Gong Xueyu; Li Xinxia; Yu Jun

2012-01-01

The bootstrap current of fast ions produced by neutral beam injection (NBI) is investigated in a large-aspect-ratio tokamak with circular cross-section under specific parameters. The bootstrap current density distribution and the total bootstrap current are reported. In addition, the beam bootstrap current always accompanies the electron return current due to the parallel momentum transfer from fast ions. With the electron return current taken into consideration, the net current density obviously decreases; at the same time, the peak of the current moves towards the central plasma. Numerical results show that the value of the net current depends sensitively not only on the angle of the NBI but also on the ratio of the velocity of fast ions to the critical velocity: the value of the net current is small for neutral beam parallel injection, but increases severalfold for perpendicular injection, and increases with increasing beam energy. (paper)

A fast fault protection based on direction of bus-side capacitor discharge current for a high-surety power supply

DEFF Research Database (Denmark)

Li, Haijin; Chen, Min; Yang, Boping

2017-01-01

A short-circuit fault protection strategy based on the direction of bus-side capacitor discharge current for a high-surety power supply, known as Super Uninterruptable Power Supply (Super UPS), is studied in this paper. It consists of multiple energy sources and storage components. All energy...... strategy is necessary to keep the uninterruptable power for the critical load. In this paper, the characteristics of the short-circuit fault are analyzed first. Then, a fast short-circuit fault locating and isolating strategy based on the direction of the discharge current of the busside capacitors...

Bootstrap current of fast ions in neutral beam injection heating

International Nuclear Information System (INIS)

Huang Qianhong; Gong Xueyu; Yang Lei; Li Xinxia; Lu Xingqiang; Yu Jun

2012-01-01

The bootstrap current of fast ions produced by the neutral beam injection is investigated in a large aspect ratio tokamak with circular cross-section under specific parameters. The bootstrap current density distribution and the total bootstrap current are figured out. In addition, the beam bootstrap current always accompanies the electron return current due to the parallel momentum transfer from fast ions. With the electron return current considered, the net current density obviously decreases due to electron return current, at the same time the peak of current moves towards the centre plasma. Numerical results show that the value of the net current depends sensitively not only on the angle of the neutral beam injection but also on the ratio of the velocity of fast ions to the critical velocity: the value of net current is small for the neutral beam parallel injection but increases multipliedly for perpendicular injection, and increases with beam energy increasing. (authors)

Spectral Effects on Fast Wave Core Heating and Current Drive

International Nuclear Information System (INIS)

Phillips, C.K.; Bell, R.E.; Berry, L.A.; Bonoli, P.T.; Harvey, R.W.; Hosea, J.C.; Jaeger, E.F.; LeBlanc, B.P.; Ryan, P.M.; Taylor, G.; Valeo, E.J.; Wilson, J.R.; Wright, J.C.; Yuh, H. and the NSTX Team

2009-01-01

Recent results obtained with high harmonic fast wave (HHFW) heating and current drive (CD) on NSTX strongly support the hypothesis that the onset of perpendicular fast wave propagation right at or very near the launcher is a primary cause for a reduction in core heating efficiency at long wavelengths that is also observed in ICRF heating experiments in numerous tokamaks. A dramatic increase in core heating efficiency was first achieved in NSTX L-mode helium majority plasmas when the onset for perpendicular wave propagation was moved away from the antenna and nearby vessel structures. Efficient core heating in deuterium majority L mode and H mode discharges, in which the edge density is typically higher than in comparable helium majority plasmas, was then accomplished by reducing the edge density in front of the launcher with lithium conditioning and avoiding operational points prone to instabilities. These results indicate that careful tailoring of the edge density profiles in ITER should be considered to limit rf power losses to the antenna and plasma facing materials. Finally, in plasmas with reduced rf power losses in the edge regions, the first direct measurements of high harmonic fast wave current drive were obtained with the motional Stark effect (MSE) diagnostic. The location and radial dependence of HHFW CD measured by MSE are in reasonable agreement with predictions from both full wave and ray tracing simulations

Fast-wave current drive modelling for large non-circular tokamaks

International Nuclear Information System (INIS)

Batchelor, D.B.; Goldfinger, R.C.; Jaeger, E.F.; Carter, M.D.; Swain, D.W.; Ehst, D.; Karney, C.F.F.

1990-01-01

It is widely recognized that a key element in the development of an attractive tokamak reactor, and in the successful achievement of the mission of ITER, is the development of an efficient steady-state current drive technique. Fast waves in the ion cyclotron range of frequencies hold the promise to drive steady-state currents with the required efficiency and to effectively heat the plasma to ignition. Advantages over other heating and current drive techniques include low cost per watt and the ability to penetrate to the center of high-density plasmas. The primary issues that must be resolved are: can an antenna array be designed to radiate the required spectrum of waves and have adequate coupling properties? Will the rf power be efficiently absorbed by electrons in the desired velocity range without unacceptable parasitic damping by fuel ions or α particles? What will the efficiency of current drive be when toroidal effects such as trapped particles are included? Can a practical rf system be designed and integrated into the device? We have addressed these issues by performing extensive calculations with ORION, a 2-D code, and the ray tracing code RAYS, which calculate wave propagation, absorption and current drive in tokamak geometry, and with RIP, a 2-D code that self-consistently calculates current drive with MHD equilibrium. An important figure of merit in this context is the integrated, normalized current drive efficiency. The calculations that we present here emphasize the ITER device. We consider a low-frequency scenario such that no ion resonances appear in the machine, and a high-frequency scenario such that the deuterium second harmonic resonance is just outside the plasma and the tritium second harmonic is in the plasma, midway between the magnetic axis and the inside edge. In both cases electron currents are driven by combined TTMP and Landau damping of the fast waves

Fast computational scheme for feedback control of high current fusion tokamaks

International Nuclear Information System (INIS)

Dong, J.Q.; Khayrutdinov, R.; Azizov, E.; Jardin, S.

1992-01-01

An accurate and fast numerical model of tokamak plasma evolution is presented. In this code (DINA) the equilibrium problem of plasmas with free boundaries in externally changing magnetic fields is solved simultaneously with the plasma transport equation. The circuit equations are solved for the vacuum vessel and passive and active coils. The code includes pellet injection, neutral beam heating, auxiliary heating, and alpha particle heating. Bootstrap and beam-driven plasma currents are accounted for. An inverse variable technique is utilized to obtain the coordinates of the equilibrium magnetic surfaces. This numerical algorithm permits to determine the flux coordinates very quickly and accurately. The authors show that using the fully resistive MHD analysis the region of stability (to vertical motions) is wider than using the rigid displacement model. Comparing plasma motions with the same gain, it is seen that the plasma oscillates more in the rigid analysis than in the MHD analysis. They study the influence of the pick up coil's location and the possibility of control of the plasma vertical position. They use a simple modification of the standard control law that enables the control of the plasma with pick up coils located at any position. This flexibility becomes critical in the design of future complex high current tokamak systems. The fully resistive MHD model permits to obtain accurate estimates of the plasma response. This approach yields computational time savings of one to two orders of magnitude with respect to other existing MHD models. In this sense, conventional numerical algorithms do not provide suitable models for application of modern control techniques into real time expert systems. The proposed inverse variable technique is rather suitable for incorporation in a comprehensive expert system for feedback control of fusion tokamaks in real time

Predictions of fast wave heating, current drive, and current drive antenna arrays for advanced tokamaks

International Nuclear Information System (INIS)

Batchelor, D.B.; Baity, F.W.; Carter, M.D.

1994-01-01

The objective of the advanced tokamak program is to optimize plasma performance leading to a compact tokamak reactor through active, steady state control of the current profile using non-inductive current drive and profile control. To achieve these objectives requires compatibility and flexibility in the use of available heating and current drive systems--ion cyclotron radio frequency (ICRF), neutral beams, and lower hybrid. For any advanced tokamak, the following are important challenges to effective use of fast waves in various roles of direct electron heating, minority ion heating, and current drive: (1) to employ the heating and current drive systems to give self-consistent pressure and current profiles leading to the desired advanced tokamak operating modes; (2) to minimize absorption of the fast waves by parasitic resonances, which limit current drive; (3) to optimize and control the spectrum of fast waves launched by the antenna array for the required mix of simultaneous heating and current drive. The authors have addressed these issues using theoretical and computational tools developed at a number of institutions by benchmarking the computations against available experimental data and applying them to the specific case of TPX

The high current, fast, 100ns, Linear Transformer Driver (LTD) developmental project at Sandia Laboratories and HCEI

International Nuclear Information System (INIS)

Ward, Kevin S.; Long, Finis W.; Sinebryukhov, Vadim A.; Kim, Alexandre A.; 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; Savage, Mark Edward; Stygar, William A.; LeChien, Keith R.; Matzen, Maurice Keith

2010-01-01

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. An extensive evaluation of the LTD technology is being performed at SNL and the High Current Electronic Institute (HCEI) in Tomsk Russia. Two types of High Current LTD cavities (LTD I-II, and 1-MA LTD) were constructed and tested individually and in a voltage adder configuration (1-MA cavity only). All cavities performed remarkably well and the experimental results are in full agreement with analytical and numerical calculation predictions. A two-cavity voltage adder is been assembled and currently undergoes evaluation. This is the first step towards the completion of the 10-cavity, 1-TW module. This MYKONOS voltage adder will be the first ever IVA built with a transmission line insulated with deionized water. The LTD II cavity renamed LTD III will serve as a test bed for evaluating a number of different types of switches, resistors, alternative capacitor configurations, cores

Characterization of LH induced current carrying fast electrons in JET

Energy Technology Data Exchange (ETDEWEB)

Ramponi, G.; Airoldi, A. [Consiglio Nazionale delle Ricerche, Milan (Italy). Lab. di Fisica del Plasma; Bartlett, D.; Brusati, M.; Froissard, P.; Gormezano, C.; Rimini, F.; Silva, R.P. da; Tanzi, C.P. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking

1992-12-31

Lower Hybrid Current Drive (LHCD) experiments have recently been made at JET by coupling up to 2.4 MW of RF power at 3.7 GHz, with a power spectrum centered at n{sub ||} = 1.8 {+-} 0.2 corresponding to a resonating electron energy of about 100 keV via Electron Landau Damping. The Current Drive (CD) efficiency has been observed to increase when LH and ICRH power are applied simultaneously to the plasma, suggesting that a part of the fast magnetosonic wave is absorbed on the LH-generated fast electrons. An important problem of CD experiments in tokamaks is the determination of the radial distribution of the driven current and the characterization in the momentum space of the current carrying fast electrons by using appropriate diagnostic tools. For this purpose, a combined analysis of the Electron Cyclotron Emission (ECE) and of the Fast Electron Bremsstrahlung (FEB) measurements has been made, allowing the relevant parameters of the suprathermal electrons to be estimated. (author) 5 refs., 5 figs., 2 tabs.

Characterization of LH induced current carrying fast electrons in JET

International Nuclear Information System (INIS)

Ramponi, G.; Airoldi, A.; Bartlett, D.; Brusati, M.; Froissard, P.; Gormezano, C.; Rimini, F.; Silva, R.P. da; Tanzi, C.P.

1992-01-01

Lower Hybrid Current Drive (LHCD) experiments have recently been made at JET by coupling up to 2.4 MW of RF power at 3.7 GHz, with a power spectrum centered at n || = 1.8 ± 0.2 corresponding to a resonating electron energy of about 100 keV via Electron Landau Damping. The Current Drive (CD) efficiency has been observed to increase when LH and ICRH power are applied simultaneously to the plasma, suggesting that a part of the fast magnetosonic wave is absorbed on the LH-generated fast electrons. An important problem of CD experiments in tokamaks is the determination of the radial distribution of the driven current and the characterization in the momentum space of the current carrying fast electrons by using appropriate diagnostic tools. For this purpose, a combined analysis of the Electron Cyclotron Emission (ECE) and of the Fast Electron Bremsstrahlung (FEB) measurements has been made, allowing the relevant parameters of the suprathermal electrons to be estimated. (author) 5 refs., 5 figs., 2 tabs

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

Science.gov (United States)

1995-07-01

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

Model for ICRF fast wave current drive in self-consistent MHD equilibria

International Nuclear Information System (INIS)

Bonoli, P.T.; Englade, R.C.; Porkolab, M.; Fenstermacher, M.E.

1993-01-01

Recently, a model for fast wave current drive in the ion cyclotron radio frequency (ICRF) range was incorporated into the current drive and MHD equilibrium code ACCOME. The ACCOME model combines a free boundary solution of the Grad Shafranov equation with the calculation of driven currents due to neutral beam injection, lower hybrid (LH) waves, bootstrap effects, and ICRF fast waves. The equilibrium and current drive packages iterate between each other to obtain an MHD equilibrium which is consistent with the profiles of driven current density. The ICRF current drive package combines a toroidal full-wave code (FISIC) with a parameterization of the current drive efficiency obtained from an adjoint solution of the Fokker Planck equation. The electron absorption calculation in the full-wave code properly accounts for the combined effects of electron Landau damping (ELD) and transit time magnetic pumping (TTMP), assuming a Maxwellian (or bi-Maxwellian) electron distribution function. Furthermore, the current drive efficiency includes the effects of particle trapping, momentum conserving corrections to the background Fokker Planck collision operator, and toroidally induced variations in the parallel wavenumbers of the injected ICRF waves. This model has been used to carry out detailed studies of advanced physics scenarios in the proposed Tokamak Physics Experiment (TPX). Results are shown, for example, which demonstrate the possibility of achieving stable equilibria at high beta and high bootstrap current fraction in TPX. Model results are also shown for the proposed ITER device

Fast wave current drive in H mode plasmas on the DIII-D tokamak

International Nuclear Information System (INIS)

Petty, C.C.; Grassie, J.S. de; Baity, F.W.

1999-01-01

Current driven by fast Alfven waves is measured in H mode and VH mode plasmas on the DIII-D tokamak for the first time. Analysis of the poloidal flux evolution shows that the fast wave current drive profile is centrally peaked but sometimes broader than theoretically expected. Although the measured current drive efficiency is in agreement with theory for plasmas with infrequent ELMs, the current drive efficiency is an order of magnitude too low for plasmas with rapid ELMs. Power modulation experiments show that the reduction in current drive with increasing ELM frequency is due to a reduction in the fraction of centrally absorbed fast wave power. The absorption and current drive are weakest when the electron density outside the plasma separatrix is raised above the fast wave cut-off density by the ELMs, possibly allowing an edge loss mechanism to dissipate the fast wave power since the cut-off density is a barrier for fast waves leaving the plasma. (author)

Fast measure proceeding of weak currents

International Nuclear Information System (INIS)

Taieb, J.

1953-01-01

The process of fast measure of the weak currents that we are going to describe briefly apply worthy of the provided currents by the sources to elevated value internal resistance, as it is the case for the ionization chamber, the photocells, mass spectroscopic tubes. The problem to measure weak currents is essentially a problem of amplifier and of input circuit. We intended to achieve a whole amplifier and input circuit with advanced performances, meaning that for a measured celerity we wanted to have an signal/noise ratio the most important as in the classic systems and for a same report signal/noise a more quickly done measure. (M.B.) [fr

Fast Beam Current Change Monitor for the LHC

CERN Document Server

Kral, Jan

Stringent demands on the LHC safety and protection systems require improved methods of detecting fast beam losses. The Fast Beam Current Transformer (FBCT) is a measurement instrument, providing information about bunch-to-bunch intensity of the accelerated beam. This thesis describes the development of a new protection system based on the FBCT signal measurements. This system, the Fast Beam Current Change Monitor (FBCCM), measures the FBCT signal in a narrow frequency band and computes time derivation of the beam signal magnitude. This derivation is proportional to the beam losses. When the losses exceed a certain level, the FBCCM requests a beam dump in order to protect the LHC. The LHC protection will be ensured by four FBCCMs which will be installed into the LHC in July 2014. Six FBCCMs have been already constructed and their characteristics were measured with satisfactory results. The FBCCMs were tested by a laboratory simulation of the real LHC environment.

Fast wave current drive above the slow wave density limit

International Nuclear Information System (INIS)

McWilliams, R.; Sheehan, D.P.; Wolf, N.S.; Edrich, D.

1989-01-01

Fast wave and slow wave current drive near the mean gyrofrequency were compared in the Irvine Torus using distinct phased array antennae of similar principal wavelengths, frequencies, and input powers. The slow wave current drive density limit was measured for 50ω ci ≤ω≤500ω ci and found to agree with trends in tokamaks. Fast wave current drive was observed at densities up to the operating limit of the torus, demonstrably above the slow wave density limit

A high current, high speed pulser using avalanche transistors

International Nuclear Information System (INIS)

Hosono, Yoneichi; Hasegawa, Ken-ichi

1985-01-01

A high current, high speed pulser for the beam pulsing of a linear accelerator is described. It uses seven avalanche transistors in cascade. Design of a trigger circuit to obtain fast rise time is discussed. The characteristics of the pulser are : (a) Rise time = 0.9 ns (FWHM) and (d) Life time asymptotically equals 2000 -- 3000 hr (at 50 Hz). (author)

Fast-ion transport and neutral beam current drive in ASDEX upgrade

DEFF Research Database (Denmark)

Geiger, B.; Weiland, M.; Jacobsen, Asger Schou

2015-01-01

The neutral beam current drive efficiency has been investigated in the ASDEX Upgrade tokamak by replacing on-axis neutral beams with tangential off-axis beams. A clear modification of the radial fast-ion profiles is observed with a fast-ion D-alpha diagnostic that measures centrally peaked profiles...... during on-axis injection and outwards shifted profiles during off-axis injection. Due to this change of the fast-ion population, a clear modification of the plasma current profile is predicted but not observed by a motional Stark effect diagnostic. The fast-ion transport caused by MHD activity has been...

Approach to high stability beta limit and its control by fast wave current drive in reversed field pinch plasma

International Nuclear Information System (INIS)

Kusano, K.; Kondoh, Y.; Gesso, H.; Osanai, Y.; Saito, K.N.; Ukai, R.; Nanba, T.; Nagamine, Y.; Shiina, S.

2001-01-01

Before the generation of steady state, dynamo-free RFP configuration by rf current driving scheme, it is necessary to find an optimum configuration into high stability beta limit against m=1 resonant resistive MHD modes and reducing nonlinearly turbulent level with less rf power. As first step to the optimization study, we are interested in partially relaxed state model (PRSM) RFP configuration, which is considered to be closer to a relaxed state at finite beta since it has force-free fields for poloidal direction with a relatively shorter characteristic length of relaxation and a relatively higher stability beta limit to m=1 resonant ideal MHD modes. The stability beta limit to m=1 resonant resistive MHD modes can be predicted to be relatively high among other RFP models and to be enhanced by the current density profile control using fast magnetosonic waves (FMW), which are accessible to high density region with strong absorption rate. (author)

Predictions of of fast wave heating, current drive, and current drive antenna arrays for advanced tokamaks

International Nuclear Information System (INIS)

Batchelor, D.B.; Baity, F.W.; Carter, M.D.

1995-01-01

The objective of the advanced tokamak program is to optimize plasma performance leading to a compact tokamak reactor through active, steady state control of the current profile using non-inductive current drive and profile control. To achieve this objective requires compatibility and flexibility in the use of available heating and current drive systems - ion cyclotron radio frequency (ICRF), neutral beams, and lower hybrid. For any advanced tokamak, the following are important challenges to effective use of fast waves in various role of direct electron heating, minority ion heating, and current drive: (1) to employ the heating and current drive systems to give self-consistent pressure and current profiles leading to the desired advanced tokamak operating modes; (2) to minimize absorption of the fast waves by parasitic resonances, which limit current drive; (3) to optimize and control the spectrum of fast waves launched by the antenna array for the required mix of simultaneous heating and current drive. The paper addresses these issues using theoretical and computational tools developed at a number of institutions by benchmarking the computations against available experimental data and applying them to the specific case of TPX. (author). 6 refs, 3 figs

RF high voltage performance of RF transmission line components on the DIII-D Fast Wave Current Drive (FWCD) system

International Nuclear Information System (INIS)

Ferguson, S.W.; Callis, R.W.; Cary, W.P.; Phelps, D.A.; Ponce, D.; Baity, F.W.; Barber, G.

1995-01-01

The performance of the high voltage rf components of the DIII-D Fast Wave Current Drive System (FWCD) have been evaluated under various conditions of insulator configuration, insulator material, insulating gas and gas pressure. The insulator materials that have been investigated are alumina, steatite, pyrex, quartz, and teflon. The results of this evaluation are discussed in this paper. Additionally a rf high potter was developed to aid in the evaluation of rf high voltage components. The high potter consists of a 50 Ω, 1/4 wavelength cavity with a variable position short and a 50 ohm matched tap at one end of the cavity. With this configuration rf voltages were generated in excess of 100 kVp in the frequency range 30 to 60 MHz

RF high voltage performance of RF transmission line components on the DIII-D Fast Wave Current Drive (FWCD) System

International Nuclear Information System (INIS)

Ferguson, S.W.; Callis, R.W.; Cary, W.P.; Phelps, D.A.; Ponce, D.; Baity, F.W.; Barber, G.

1995-12-01

The performance of the high voltage rf components of the DIII-D Fast Wave Current Drive System (FWCD) have been evaluated under various conditions of insulator configuration, insulator material, insulating gas and gas pressure. The insulator materials that have been investigated are alumina, steatite, pyrex, quartz, and teflon. The results of this evaluation are discussed in this paper. Additionally a rf high potter was developed to aid in the evaluation of rf high voltage components. The high potter consists of a 50 Ω, 1/4 wavelength cavity with a variable position short and a 50 ohm matched tap at one end of the cavity. With this configuration rf voltages were generated in excess of 100 kVp in the frequency range 30 to 60 MHz

Sausage instabilities in electron current channels and the problem of fast ignition

International Nuclear Information System (INIS)

Das, A.

2002-01-01

In the fast ignition concept of laser fusion, an intense picosecond laser pulse incident on an overdense pellet is absorbed by nonlinear mechanisms and gets converted into inward propagating fast electron currents. PIC simulations show that the return shielding currents due to cold plasma interact with the incoming currents and intense Weibel, tearing and coalescence instabilities take place, which organize the current into a few current channels. The stability of these current channels is thus a topic of great interest. We have carried out linear and nonlinear studies of 2 - dimensional sausage instabilities of a slab model of the current channels in the framework of electron magnetohydrodynamic fluid approximation. The analytic calculations and numerical simulations for some simple velocity profiles show the presence of linear instability driven by velocity shear. Nonlinear studies on the saturation of instabilities and their reaction back on the relaxation of the velocity profile have also been made. A discussion of the consequences of such EMHD turbulence induced relaxation and stopping of fast electrons, for the fast ignition concept will be presented. (author)

Full-wave simulations of current profiles for fast magnetosonic wave current drive

International Nuclear Information System (INIS)

Dmitrieva, M.V.; Eriksson, L.-G.; Gambier, D.J.

1992-12-01

Numerical simulations of current drive in tokamaks by fast waves (FWCD) have been performed in the range of the ion cyclotron and at lower frequencies via 3-Dimensional numerical code ICTOR. Trapped particles effects were taken into account in the calculation of the fast wave current drive efficiency and the bootstrap current generation. The global efficiency of FWCD if found to be γ∼ 0.1 x 10 20 AW -1 m -2 for the Joint European Torus tokamak (JET) parameters at a central electron temperature of ∼ 10 kev. The efficiency of FWCD for reactor-like plasmas is found to be γ∼0.3 x 10 20 AW -1 m -2 for ∼ 100% of FWCD and γ∼ 1 x 10 20 AW -1 m -2 for FWCD and ∼ 65% of bootstrap in a total current of ∼ 25MA at a 25kev central temperature with a density of ∼10 20 m -3 and major radius R ∼ 8m. Non-inductive current density profiles are studied. Broad FWCD current profiles are obtained for flat reactor temperature and density profiles with bootstrap current concentrated at the plasma edge. The possibility of a steady-state reactor on full wave (FW) with a large fraction of bootstrap current is discussed. It appears to be impractical to rely on such an external current driven (CD) scheme for a reactor as long a γ is less than 2 x 10 20 AW -1 m -2 . (Author)

Experimentally determined profiles of fast wave current drive on DIII-D

International Nuclear Information System (INIS)

Forest, C.B.; Petty, C.C.; Baity, F.W.; Chiu, S.C.; deGrassie, J.S.; Groebner, R.J.; Ikezi, H.; Jaeger, E.F.; Kupfer, K.; Murakami, M.; Pinsker, R.I.; Prater, R.; Rice, B.W.; Wade, M.R.; Whyte, D.G.

1996-01-01

Profiles of non-inductive current driven by fast waves have been determined for reversed-shear DIII-D discharges. Both the current profile and toroidal electric field profile are determined from time sequences of equilibrium reconstructions [C. B. Forest et al., Phys. Rev. Lett. 73, 2224 (1994)]. Using this information, the measured current profile has been separated into inductive and non-inductive portions. By comparing similar discharges with co and counter antenna phasings and similar fast wave power, the portion of the total non-inductive current driven by fast waves was determined. The experimentally determined profiles of FWCD are in general agreement with theoretical predictions. Specifically, 135 kA was driven by 1.4 MW of rf power with a profile peaked inside ρ=2. copyright 1996 American Institute of Physics

Fast wave and electron cyclotron current drive in the DIII-D tokamak

International Nuclear Information System (INIS)

Petty, C.C.; Pinsker, R.I.; Austin, M.E.

1995-01-01

The non-inductive current drive from directional fast Alfven and electron cyclotron waves was measured in the DIII-D tokamak in order to demonstrate these forms of radiofrequency (RF) current drive and to compare the measured efficiencies with theoretical expectations. The fast wave frequency was 8 times the deuterium cyclotron frequency at the plasma centre, while the electron cyclotron wave was at twice the electron cyclotron frequency. Complete non-inductive current drive was achieved using a combination of fast wave current drive (FWCD) and electron cyclotron current drive (ECCD) in discharges for which the total plasma current was inductively ramped down from 400 to 170 kA. For steady current discharges, an analysis of the loop voltage revealed up to 195 kA of a non-inductive current (out of 310 kA) during combined electron cyclotron and fast wave injection, with a maximum of 110 kA of FWCD and 80 kA of ECCD achieved (not simultaneously). The peakedness of the current profile increased with RF current drive, indicating that the driven current was centrally localized. The FWCD efficiency increased linearly with the central electron temperature as expected; however, the FWCD was severely degraded in low current discharges owing to incomplete fast wave absorption. The measured FWCD agreed with the predictions of a ray tracing code only when a parasitic loss of 4% per pass was included in the modelling along with multiple pass absorption. Enhancement of the second harmonic ECCD efficiency by the toroidal electric field was observed experimentally. The measured ECCD was in good agreement with Fokker-Planck code predictions. (author). 41 refs, 13 figs, 1 tab

Fast-ion transport in qmin>2, high-β steady-state scenarios on DIII-D

International Nuclear Information System (INIS)

Holcomb, C. T.; Heidbrink, W. W.; Collins, C.; Ferron, J. R.; Van Zeeland, M. A.; Garofalo, A. M.; Bass, E. M.; Luce, T. C.; Pace, D. C.; Solomon, W. M.; Mueller, D.; Grierson, B.; Podesta, M.; Gong, X.; Ren, Q.; Park, J. M.; Kim, K.; Turco, F.

2015-01-01

Results from experiments on DIII-D [J. L. Luxon, Fusion Sci. Technol. 48, 828 (2005)] aimed at developing high β steady-state operating scenarios with high-q min confirm that fast-ion transport is a critical issue for advanced tokamak development using neutral beam injection current drive. In DIII-D, greater than 11 MW of neutral beam heating power is applied with the intent of maximizing β N and the noninductive current drive. However, in scenarios with q min >2 that target the typical range of q 95 = 5–7 used in next-step steady-state reactor models, Alfvén eigenmodes cause greater fast-ion transport than classical models predict. This enhanced transport reduces the absorbed neutral beam heating power and current drive and limits the achievable β N . In contrast, similar plasmas except with q min just above 1 have approximately classical fast-ion transport. Experiments that take q min >3 plasmas to higher β P with q 95 = 11–12 for testing long pulse operation exhibit regimes of better than expected thermal confinement. Compared to the standard high-q min scenario, the high β P cases have shorter slowing-down time and lower ∇β fast , and this reduces the drive for Alfvénic modes, yielding nearly classical fast-ion transport, high values of normalized confinement, β N , and noninductive current fraction. These results suggest DIII-D might obtain better performance in lower-q 95 , high-q min plasmas using broader neutral beam heating profiles and increased direct electron heating power to lower the drive for Alfvén eigenmodes

60 MHz fast wave current drive experiment for DIII-D

Energy Technology Data Exchange (ETDEWEB)

Mayberry, M.J.; Chiu, S.C.; Porkolab, M.; Chan, V.; Freeman, R.; Harvey, R.; Pinsker, R. (General Atomics, San Diego, CA (USA))

1989-07-01

The DIII-D facility provides an opportunity to test fast wave current drive appoach. Efficient FWCD is achieved by direct electron absorption due to Landa damping and transit time magnetic pumping. To avoid competing damping mechamisms we seek to maximize the single-pass asorption of the fast waves by electrons. (AIP)

Current status and perspective of advanced loop type fast reactor in fast reactor cycle technology development project

International Nuclear Information System (INIS)

Niwa, Hajime; Aoto, Kazumi; Morishita, Masaki

2007-01-01

After selecting the combination of the sodium-cooled fast reactor (SFR) with oxide fuel, the advanced aqueous reprocessing and the simplified pelletizing fuel fabrication as the most promising concept of FR cycle system, 'Feasibility Study on Commercialized Fast Reactor Cycle Systems' was finalized in 2006. Instead, a new project, Fast Reactor Cycle Technology Development Project (FaCT Project) was launched in Japan focusing on development of the selected concepts. This paper describes the current status and perspective of the advanced loop type SFR system in the FaCT Project, especially on the design requirements, current design as well as the related innovative technologies together with the development road-map. Some considerations on advantages of the advanced loop type design are also described. (authors)

Effect of discrete RF spectrum on fast wave current drive

International Nuclear Information System (INIS)

Okazaki, Takashi; Yoshioka, Ken; Sugihara, Masayoshi

1987-08-01

Effect of discrete RF spectrum has been studied for the fast wave current drive with the ion cyclotron range of frequency. Driven current and power densities decrease in this spectrum than in the continuous spectrum. However, there is a possibility to have the mechanism which allows electrons outside the resonance region to interact with the fast wave, taking into account the electron trapping by discrete RF spectrum. In the case of neglecting the electron trapping effect, driven current and power densities decrease up to 0.6 - 0.8 of those which are obtained for the continuous spectrum for the FER (Fusion Experimental Reactor). However, their driven current and power densities can be almost doubled in their magnitude for the discrete spectrum by taking into account the trapping effect. (author)

Fast electron current density profile and diffusion studies during LHCD in PBX-M

International Nuclear Information System (INIS)

Jones, S.E.; Kesner, J.; Luckhardt, S.; Paoletti, F.

1993-08-01

Successful current profile control experiments using lower hybrid current drive (LCHD) clearly require knowledge of (1) the location of the driven fast electrons and (2) the ability to maintain that location from spreading due to radial diffusion. These issues can be addressed by examining the data from the hard x-ray camera on PBX-M, a unique diagnostic producing two-dimensional, time resolved tangential images of fast electron bremsstrahlung. Using modeling, these line-of-sight images are inverted to extract a radial fast electron current density profile. We note that ''hollow'' profiles have been observed, indicative of off-axis current drive. These profiles can then be used to calculate an upper bound for an effective fast electron diffusion constant: assuming an extremely radially narrow lower hybrid absorption profile and a transport model based on Rax and Moreau, a model fast electron current density profile is calculated and compared to the experimentally derived profile. The model diffusion constant is adjusted until a good match is found. Applied to steady-state quiescent modes on PBX-M, we obtain an upper limit for an effective diffusion constant of about D*=1.1 m 2 /sec

Current neutralization of nanosecond risetime, high-current electron beam

International Nuclear Information System (INIS)

Lidestri, J.P.; Spence, P.W.; Bailey, V.L.; Putnam, S.D.; Fockler, J.; Eichenberger, C.; Champney, P.D.

1991-01-01

This paper reports that the authors have recently investigated methods to achieve current neutralization in fast risetime (<3 ns) electron beams propagating in low-pressure gas. For this investigation, they injected a 3-MV, 30-kA intense beam into a drift cell containing gas pressures from 0.10 to 20 torr. By using a fast net current monitor (100-ps risetime), it was possible to observe beam front gas breakdown phenomena and to optimize the drift cell gas pressure to achieve maximum current neutralization. Experimental observations have shown that by increasing the drift gas pressure (P ∼ 12.5 torr) to decrease the mean time between secondary electron/gas collisions, the beam can propagate with 90% current neutralization for the full beam pulsewidth (16 ns)

A thermodynamical analysis of rf current drive with fast electrons

Energy Technology Data Exchange (ETDEWEB)

Bizarro, João P. S., E-mail: bizarro@ipfn.tecnico.ulisboa.pt [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa (Portugal)

2015-08-15

The problem of rf current drive (CD) by pushing fast electrons with high-parallel-phase-velocity waves, such as lower-hybrid (LH) or electron-cyclotron (EC) waves, is revisited using the first and second laws, the former to retrieve the well-known one-dimensional (1D) steady-state CD efficiency, and the latter to calculate a lower bound for the rate of entropy production when approaching steady state. The laws of thermodynamics are written in a form that explicitly takes care of frictional dissipation and are thus applied to a population of fast electrons evolving under the influence of a dc electric field, rf waves, and collisions while in contact with a thermal, Maxwellian reservoir with a well-defined temperature. Besides the laws of macroscopic thermodynamics, there is recourse to basic elements of kinetic theory only, being assumed a residual dc electric field and a strong rf drive, capable of sustaining in the resonant region, where waves interact with electrons, a raised fast-electron tail distribution, which becomes an essentially flat plateau in the case of the 1D theory for LHCD. Within the 1D model, particularly suited for LHCD as it solely retains fast-electron dynamics in velocity space parallel to the ambient magnetic field, an H theorem for rf CD is also derived, which is written in different forms, and additional physics is recovered, such as the synergy between the dc and rf power sources, including the rf-induced hot conductivity, as well as the equation for electron-bulk heating. As much as possible 1D results are extended to 2D, to account for ECCD by also considering fast-electron velocity-space dynamics in the direction perpendicular to the magnetic field, which leads to a detailed discussion on how the definition of an rf-induced conductivity may depend on whether one works at constant rf current or power. Moreover, working out the collisional dissipated power and entropy-production rate written in terms of the fast-electron distribution, it

Simulation of enhanced tokamak performance on DIII-D using fast wave current drive

International Nuclear Information System (INIS)

Grassie, J.S. de; Lin-Liu, Y.R.; Petty, C.C.; Pinsker, R.I.; Chan, V.S.; Prater, R.; John, H. St.; Baity, F.W.; Goulding, R.H.; Hoffman, D.H.

1993-01-01

The fast magnetosonic wave is now recognized to be a leading candidate for noninductive current drive for the tokamak reactor due to the ability of the wave to penetrate to the hot dense core region. Fast wave current drive (FWCD) experiments on DIII-D have realized up to 120 kA of rf current drive, with up to 40% of the plasma current driven noninductively. The success of these experiments at 60 MHz with a 2 MW transmitter source capability has led to a major upgrade of the FWCD system. Two additional transmitters, 30 to 120 MHz, with a 2 MW source capability each, will be added together with two new four-strap antennas in early 1994. Another major thrust of the DIII-D program is to develop advanced tokamak modes of operation, simultaneously demonstrating improvements in confinement and stability in quasi-steady-state operation. In some of the initial advanced tokamak experiments on DIII-D with neutral beam heated (NBI) discharges it has been demonstrated that energy confinement time can be improved by rapidly elongating the plasma to force the current density profile to be more centrally peaked. However, this high-l i phase of the discharge with the commensurate improvement in confinement is transient as the current density profile relaxes. By applying FWCD to the core of such a κ-ramped discharge it may be possible to sustain the high internal inductance and elevated confinement. Using computational tools validated on the initial DIII-D FWCD experiments we find that such a high-l i advanced tokamak discharge should be capable of sustainment at the 1 MA level with the upgraded capability of the FWCD system. (author) 16 refs., 3 figs., 1 tab

A current drive by using the fast wave in frequency range higher than two timeslower hybrid resonance frequency on tokamaks

Directory of Open Access Journals (Sweden)

Kim Sun Ho

2017-01-01

Full Text Available An efficient current drive scheme in central or off-axis region is required for the steady state operation of tokamak fusion reactors. The current drive by using the fast wave in frequency range higher than two times lower hybrid resonance (w>2wlh could be such a scheme in high density, high temperature reactor-grade tokamak plasmas. First, it has relatively higher parallel electric field to the magnetic field favorable to the current generation, compared to fast waves in other frequency range. Second, it can deeply penetrate into high density plasmas compared to the slow wave in the same frequency range. Third, parasitic coupling to the slow wave can contribute also to the current drive avoiding parametric instability, thermal mode conversion and ion heating occured in the frequency range w<2wlh. In this study, the propagation boundary, accessibility, and the energy flow of the fast wave are given via cold dispersion relation and group velocity. The power absorption and current drive efficiency are discussed qualitatively through the hot dispersion relation and the polarization. Finally, those characteristics are confirmed with ray tracing code GENRAY for the KSTAR plasmas.

Fast current ramp experiments on TFTR

International Nuclear Information System (INIS)

Fredrickson, E.D.; McGuire, K.; Goldston, R.J.

1987-05-01

Electron heat transport on TFTR and other tokamaks is several orders of magnitude larger than neoclassical calculations would predict. Despite considerable effort, there is still no clear theoretical understanding of this anomalous transport. The electron temperature profile T/sub e/(r), shape has shown a marked consistency on many machines, including TFTR, for a wide range of plasma parameters and heating profiles. This could be an important clue as to the process responsible for this enhanced thermal transport. In this paper 'profile consistency' in TFTR is described and an experiment which uses a fast current ramp to transiently decouple the current density profile J(r), and the T/sub e/(r) profiles is discussed. From this experiment the influence of J(r) on electron temperature profile consistency can be determined

Bootstrap and fast wave current drive for tokamak reactors

International Nuclear Information System (INIS)

Ehst, D.A.

1991-09-01

Using the multi-species neoclassical treatment of Hirshman and Sigmar we study steady state bootstrap equilibria with seed currents provided by low frequency (ICRF) fast waves and with additional surface current density driven by lower hybrid waves. This study applies to reactor plasmas of arbitrary aspect ratio. IN one limit the bootstrap component can supply nearly the total equilibrium current with minimal driving power ( o = 18 MA needs P FW = 15 MW, P LH = 75 MW). A computational survey of bootstrap fraction and current drive efficiency is presented. 11 refs., 8 figs

The dynamic current-voltage characteristic as a powerful tool to analyze fast phenomena in plasma

International Nuclear Information System (INIS)

Ivan, L. M.; Mihai-Plugaru, M.; Amarandei, G.; Aflori, M.; Dimitriu, D. G.

2006-01-01

The static current-voltage characteristic of an electrode immersed in plasma is obtained by slowly increasing and subsequently decreasing the potential on the electrode with respect to the plasma potential or the ground. This characteristic can give us important information about the phenomena that take place in front of the electrode. Current jumps can be evidenced which were often associated with an hysteresis effect, regions with S-type or N-type negative differential resistance, etc. The method is always used when we investigate the appearance of complex space charge configurations (CSCC) in front of an electrode immersed in plasma. However, to investigate the dynamics of such structures or other fast phenomena (like instabilities) which take place in plasma devices with frequencies of tenth, hundred kHz or more, complex investigation techniques must be used. One of the most efficient methods to investigate fast phenomena in plasma devices is the dynamic current-voltage characteristic. This is obtained by recording the time series of the current collected by the electrode when the voltage applied on it is very fast modified (most likely increased) by using a signal generator. In this way, very fast oscillations of the current can be recorded and new phenomena can be evidenced. We used this technique to study the phenomena which take place at the onset of electrostatic instabilities in Q-machine plasma, namely the potential relaxation instability (PRI) and the electrostatic ion-cyclotron instability (EICI). The obtained experimental results prove that the negative differential resistance region in the static current-voltage characteristic is the result of a nonlinear dynamics of a CSCC in form of a double layer (DL) which takes place just before the onset of the instabilities. In the case of the PRI we emphasized current jumps related with the DL appearance, which are not present in the static current-voltage characteristic at high plasma density. (authors)

Current profile evolution during fast wave current drive on the DIII-D tokamak

International Nuclear Information System (INIS)

Petty, C.C.; Forest, C.B.; Baity, F.W.

1995-06-01

The effect of co and counter fast wave current drive (FWCD) on the plasma current profile has been measured for neutral beam heated plasmas with reversed magnetic shear on the DIII-D tokamak. Although the response of the loop voltage profile was consistent with the application of co and counter FWCD, little difference was observed between the current profiles for the opposite directions of FWCD. The evolution of the current profile was successfully modeled using the ONETWO transport code. The simulation showed that the small difference between the current profiles for co and counter FWCD was mainly due to an offsetting change in the o at sign c current proffie. In addition, the time scale for the loop voltage to reach equilibrium (i.e., flatten) was found to be much longer than the FWCD pulse, which limited the ability of the current profile to fully respond to co or counter FWCD

The essential theory of fast wave current drive with full wave method

International Nuclear Information System (INIS)

Liu Yan; Gong Xueyu; Yang Lei; Yin Chenyan; Yin Lan

2007-01-01

The full wave numerical method is developed for analyzing fast wave current drive in the range of ion cyclotron waves in tokamak plasmas, taking into account finite larmor radius effects and parallel dispersion. the physical model, the dispersion relation on the assumption of Finite Larmor Radius (FLR) effects and the form of full wave be used for computer simulation are developed. All of the work will contribute to further study of fast wave current drive. (authors)

First demonstration of the fast-to-slow corrector current shift in the NSLS-II storage ring

Science.gov (United States)

Yang, Xi; Tian, Yuke; Yu, Li Hua; Smaluk, Victor

2018-04-01

To realize the full benefits of the high brightness and ultra-small beam sizes of NSLS-II, it is essential that the photon beams are exceedingly stable. In the circumstances of implementing local bumps, changing ID gaps, and long term drifting, the fast orbit feedback (FOFB) requires shifting the fast corrector strengths to the slow correctors to prevent the fast corrector saturation and to make the beam orbit stable in the sub-micron level. As the result, a reliable and precise technique of fast-to-slow corrector strength shift has been developed and tested at NSLS-II. This technique is based on the fast corrector response to the slow corrector change when the FOFB is on. In this article, the shift technique is described and the result of proof-of-principle experiment carried out at NSLS-II is presented. The maximum fast corrector current was reduced from greater than 0.45 A to less than 0.04 A with the orbit perturbation within ±1 μm.

Ion beams from high-current PF facilities

Energy Technology Data Exchange (ETDEWEB)

Sadowski, M [Soltan Inst. for Nuclear Studies, Otwock-Swierk (Poland)

1997-12-31

Pulsed beams of fast deuterons and impurity or admixture ions emitted from high-current PF-type facilities operated in different laboratories are dealt with. A short comparative analysis of time-integrated and time-resolved studies is presented. Particular attention is paid to the microstructure of such ion beams, and to the verification of some theoretical models. (author). 5 figs., 19 refs.

Study of the fast electron distribution function in lower hybrid and electron cyclotron current driven plasmas in the WT-3 tokamak

International Nuclear Information System (INIS)

Ogura, K.; Tanaka, H.; Ide, S.

1991-01-01

The distribution function f(p-vector) of fast electrons produced by lower hybrid current drive (LHCD) is investigated in the WT-3 tokamak, using a combination of measurements of the hard X-ray (HXR) angular distribution with respect to the toroidal magnetic field and observations of the HXR radial profile. The data obtained indicate the formation of a plateau-like region in f(p-vector) which corresponds to a region of resonant interaction between the lower hybrid (LH) wave and the electrons. The energy of the fast electrons in the peripheral plasma region is observed to be higher than that in the central plasma region under operational conditions with a high plasma current (I p ≥ 80 kA). At low current (I p < or approx. 50 kA), however, the energy of fast electrons is constant along the plasma radius. In the current ramp-up phase, fast electrons are generated in the directions normal to and opposite to the LH wave propagation. The latter case is ascribed to a negatively biased toroidal electric field induced by the current ramp-up. To study the characteristic change of f(p-vector) for various current drive mechanisms, HXR measurements are performed in electron cyclotron current driven (ECCD) plasma and in Ohmic heating (OH) plasma. In ECCD plasma, the perpendicular energy of fast electrons increases, which indicates that fast electrons are accelerated perpendicularly by electron cyclotron heating. In both LHCD and ECCD plasmas, fast electrons flow in the direction opposite to the wave propagation, while no such fast electrons are formed in OH plasma. (author). 33 refs, 16 figs, 1 tab

Profiles of fast ions that are accelerated by high harmonic fast waves in the National Spherical Torus Experiment

International Nuclear Information System (INIS)

Liu, D; Heidbrink, W W; Podesta, M; Ruskov, E; Bell, R E; Fredrickson, E D; Medley, S S; Harvey, R W

2010-01-01

Combined neutral beam injection and high-harmonic fast-wave (HHFW) heating accelerate deuterium fast ions in the National Spherical Torus Experiment (NSTX). With 1.1 MW of HHFW power, the neutron emission rate is about three times larger than in the comparison discharge without HHFW heating. Acceleration of fast ions above the beam injection energy is evident on an E||B type neutral particle analyzer (NPA), a 4-chord solid state neutral particle analyzer (SSNPA) array and a 16-channel fast-ion D-alpha (FIDA) diagnostic. The accelerated fast ions observed by the NPA and SSNPA diagnostics mainly come from passive charge exchange reactions at the edge due to the NPA/SSNPA localization in phase space. The spatial profile of accelerated fast ions that is measured by the FIDA diagnostic is much broader than in conventional tokamaks because of the multiple resonance layers and large orbits in NSTX. The fast-ion distribution function calculated by the CQL3D Fokker-Planck code differs from the measured spatial profile, presumably because the current version of CQL3D uses a zero-banana-width model. In addition, compressional Alfven eigenmode activity is stronger during the HHFW heating and it may affect the fast-ion spatial profile.

Simulations of ICRF-fast wave current drive on DIIID

International Nuclear Information System (INIS)

Ehst, D.A.

1990-06-01

Self-consistent calculations of MHD equilibria, generated by fast wave current drive and including the bootstrap effect, were done to guide and anticipate the results of upcoming experiments on the DIIID tokamak. The simulations predict that 2 MW of ICRF power is more than adequate to create several hundred kiloamperes in steady state; the total current increases with the temperature and density of the target plasma. 12 refs., 12 figs., 1 tab

Disintegration of fast magnetoacoustic oscillation spectra in non-uniform current-loaded plasma cylinder

International Nuclear Information System (INIS)

Girka, I.A.; Stepanov, K.N.

1990-01-01

Dispersion equation for fast plasma cylinder with longitudinal current including a weak azimuthal magnetic field β 0v is obtained and analyzed on the basis of perturbation theory. Simple asymptotic expressions for S w , S n and σ k are derived under different limiting cases (propagation of small-scale waves with high values of radial wave number, wave in the uniform cylinder, surface mode etc.). 10 refs.; 1 fig

High current, 0.5-MA, fast, 100-ns, linear transformer driver experiments

Directory of Open Access Journals (Sweden)

Michael G. Mazarakis

2009-05-01

Full Text Available The linear transformer driver (LTD is a new method for constructing high current, high-voltage pulsed accelerators. The salient feature of the approach is switching and inductively adding the pulses at low voltage straight out of the capacitors through low inductance transfer and soft iron core isolation. Sandia National Laboratories are actively pursuing the development of a new class of accelerator based on the LTD technology. Presently, the high current LTD experimental research is concentrated on two aspects: first, to study the repetition rate capabilities, reliability, reproducibility of the output pulses, switch prefires, jitter, electrical power and energy efficiency, and lifetime measurements of the cavity active components; second, to study how a multicavity linear array performs in a voltage adder configuration relative to current transmission, energy and power addition, and wall plug to output pulse electrical efficiency. Here we report the repetition rate and lifetime studies performed in the Sandia High Current LTD Laboratory. We first utilized the prototype ∼0.4-MA, LTD I cavity which could be reliably operated up to ±90-kV capacitor charging. Later we obtained an improved 0.5-MA, LTD II version that can be operated at ±100  kV maximum charging voltage. The experimental results presented here were obtained with both cavities and pertain to evaluating the maximum achievable repetition rate and LTD cavity performance. The voltage adder experiments with a series of double sized cavities (1 MA, ±100  kV will be reported in future publications.

Universal Voltage Conveyor and Current Conveyor in Fast Full-Wave Rectifier

Directory of Open Access Journals (Sweden)

Josef Burian

2012-12-01

Full Text Available This paper deals about the design of a fast voltage-mode full-wave rectifier, where universal voltage conveyor and second-generation current conveyor are used as active elements. Thanks to the active elements, the input and output impedance of the non-linear circuit is infinitely high respectively zero in theory. For the rectification only two diodes and three resistors are required as passive elements. The performance of the circuit is shown on experimental measurement results showing the dynamic range, time response, frequency dependent DC transient value and RMS error for different values of input voltage amplitudes.

Fast Food Pattern and Cardiometabolic Disorders: A Review of Current Studies.

Science.gov (United States)

Bahadoran, Zahra; Mirmiran, Parvin; Azizi, Fereidoun

2015-01-01

There are growing concern globally regarding the alarming trend of fast food consumption and its related cardiometabolic outcomes including overweight and obesity. This study aimed to review the current evidences available in relation to adverse effects of fast food pattern on cardiometa-bolic risk factors. Relevant articles including epidemiological and clinical studies with appropriate design and good quality were obtained through searches of the Medline, PubMed, Scopus databases and Google scholar with related key words including "fast foods", "processed foods", "obesity", "overweight", "insulin resistance", "diabetes", "cardiovascular disease", "metabolic syndrome", "dyslipidemia" and "hypertension". Fast food consumption and out-of-home eating behavior is a main risk factor for lower diet quality, higher calorie and fat intake and lower micronutrients density of diet. Frequent consumption of fast foods was accompanied with overweight and abdominal fat gain, impaired insulin and glucose homeostasis, lipid and lipoprotein disorders, induction of systemic inflammation and oxidative stress. Higher fast food consumption also increases the risk of developmental diabetes, metabolic syndrome and cardiovascular disease. This review provides further evidence warning us against the irreparable effects of fast food consumption on public health especially the increasing global burden of obesity and cardiovascu-lar diseases.

Rated-voltage enhancement by fast-breaking of the fault current for a resistive superconducting fault current limiter component

International Nuclear Information System (INIS)

Park, C.-R.; Kim, M.-J.; Yu, S.-D.; Yim, S.-W.; Kim, H.-R.; Hyun, O.-B.

2010-01-01

Performance of a resistive superconducting fault current limiter (SFCL) component is usually limited by temperature rise associated with energy input by fault current application during a fault. Therefore, it is expected that short application of the fault current may enhance the power ratings of the component. This can be accomplished by a combination of a HTS component and a mechanical switch. The fast switch (FS) developed recently enables the fault duration to be as short as 1/2 cycle after a fault. Various second-generation (2G) high temperature superconductors (HTS) and YBCO thin films have been tested. The relation between the rated voltage V and the fault duration time t was found to be V 2 ∼ t -1 . Based upon the relation, we predict that when the FS break the fault current within 1/2 cycle after a fault, the amount of HTS components required to build an SFCL can be reduced by as much as about 60%, of that when breaking the fault current at three cycles.

Sausage instabilities in the electron current layer and its role in the concept of fast ignition

International Nuclear Information System (INIS)

Das, Amita; Jain, Neeraj; Kaw, Predhiman; Sengupta, Sudip

2004-01-01

The fast ignition concept of laser fusion utilizes hot electrons produced at the surface of the target by an incident intense laser pulse for the creation of the hot spot for ignition. As the hot electrons move inwards to the core of the precompressed target, the electrons from the background plasma provide a return shielding current. Three dimensional PIC simulations have shown that intense Weibel, tearing and coalescence instabilities take place which organize the current distribution into a few current filaments. In each of these filaments the central core region constitutes a current due to the fast electrons propagating inwards towards the pellet core, while the outer cylindrical shell region carries the return shielding current. The presence of instabilities and their subsequent nonlinear development can hinder the propagation of fast electrons towards the core influencing the location of the hot spot for ignition. Earlier studies showing the existence of sausage-like modes were carried out in the nonrelativistic limit and under the assumption of equal electron densities of the fast and the cold electrons. The fast electron density, in general, differs considerably from the background plasma density as it is dependent on the incident laser intensity. This paper incorporates relativistic effects and also studies the dependence of the growth rate on the fast electron density. Finally, nonlinear saturation of the instability and its impact on the stopping of the fast electron motion towards the core have also been investigated using numerical simulations. The simulations have, however, currently been carried out for non-relativistic dynamics. The results show that the sheared velocity profile of the channel gets flattened, causing an effective drop in the inward moving current. (author)

Study of non-inductive current drive using high energy neutral beam injection on JT-60U

International Nuclear Information System (INIS)

Oikawa, Toshihiro

2004-01-01

The negative ion based neutral beam (N-NB) current drive was experimentally studied. The N-NB driven current density was determined over a wide range of electron temperatures by using the motional Stark effect spectroscopy. Theoretical prediction of the NB current drive increasing with beam energy and electron temperature was validated. A record value of NB current drive efficiency 1.55 x 10 19 Am -2 W -1 was achieved simultaneously with high confinement and high beta at at a plasma current of 1.5 MA under a fully non-inductively current driven condition. The experimental validation of NB current drive theory for MHD quiescent plasmas gives greater confidence in predicting the NB current drive in future reactors. However, it was also found that MHD instabilities caused a degradation of NB current drive. A beam-driven instability expelled N-NB fast ions carrying non-inductive current from the central region. The lost N-NB driven current was estimated to be 7% of the total N-NB driven current. For the neoclassical tearing mode (NTM), comparisons of the measured neutron yield and fast ion pressure profile with transport code calculations revealed that the loss of fast ions increases with the NTM activity and that fast ions at higher energies suffer larger transport than at lower energies. (author)

High temperature fast reactor for hydrogen production in Brazil

International Nuclear Information System (INIS)

Nascimento, Jamil A. do; Ono, Shizuca; Guimaraes, Lamartine N.F.

2008-01-01

The main nuclear reactors technology for the Generation IV, on development phase for utilization after 2030, is the fast reactor type with high temperature output to improve the efficiency of the thermo-electric conversion process and to enable applications of the generated heat in industrial process. Currently, water electrolysis and thermo chemical cycles using very high temperature are studied for large scale and long-term hydrogen production, in the future. With the possible oil scarcity and price rise, and the global warming, this application can play an important role in the changes of the world energy matrix. In this context, it is proposed a fast reactor with very high output temperature, ∼ 1000 deg C. This reactor will have a closed fuel cycle; it will be cooled by lead and loaded with nitride fuel. This reactor may be used for hydrogen, heat and electricity production in Brazil. It is discussed a development strategy of the necessary technologies and some important problems are commented. The proposed concept presents characteristics that meet the requirements of the Generation IV reactor class. (author)

Fast Food Pattern and Cardiometabolic Disorders: A Review of Current Studies

Directory of Open Access Journals (Sweden)

Zahra Bahadoran

2015-12-01

Full Text Available Background: There are growing concern globally regarding the alarming trend of fast food consump­tion and its related cardiometabolic outcomes including overweight and obesity. This study aimed to review the current evidences available in relation to adverse effects of fast food pattern on cardiometa­bolic risk factors. Methods: Relevant articles including epidemiological and clinical studies with appropriate design and good quality were obtained through searches of the Medline, PubMed, Scopus databases and Google scholar with related key words including "fast foods", "processed foods", "obesity", "overweight", "insulin resistance", "diabetes", "cardiovascular disease", "metabolic syndrome", "dyslipidemia" and "hypertension". Results: Fast food consumption and out-of-home eating behavior is a main risk factor for lower diet quality, higher calorie and fat intake and lower micronutrients density of diet. Frequent consumption of fast foods was accompanied with overweight and abdominal fat gain, impaired insulin and glucose homeostasis, lipid and lipoprotein disorders, induction of systemic inflammation and oxidative stress. Higher fast food consumption also increases the risk of developmental diabetes, metabolic syndrome and cardiovascular disease. Conclusion: This review provides further evidence warning us against the irreparable effects of fast food consumption on public health especially the increasing global burden of obesity and cardiovascu­lar diseases.

Fast wave current drive technology development at ORNL

International Nuclear Information System (INIS)

Baity, F.W.; Batchelor, D.B.; Goulding, R.H.; Hoffman, D.J.; Jaeger, E.F.; Ryan, P.M.; deGrassie, J.S.; Petty, C.C.; Pinsker, R.I.; Prater, R.

1993-01-01

The technology required for fast wave current drive (FWCD) systems is discussed. Experiments are underway on DIII-D, JET, and elsewhere. Antennas for FWCD draw heavily upon the experience gained in the design of ICRF heating systems with the additional requirement of launching a directional wave spectrum. Through collaborations with DIII-D, JET, and Tore Supra rapid progress is being made in the demonstration of the physics and technology of FWCD needed for TPX and ITER

Fast wave current drive technology development at ORNL

International Nuclear Information System (INIS)

Baity, F.W.; Batchelor, D.B.; Goulding, R.H.

1994-01-01

The technology required for fast wave current drive (FWCD) systems is discussed. Experiments are underway on DIII-D, JET, and elsewhere. Antennas for FWCD draw heavily upon the experience gained in the design of ICRF heating systems with the additional requirement of launching a directional wave spectrum. Through collaborations with DIII-D, JET, and Tore Supra rapid progress is being made in the demonstration of the physics and technology of FWCD needed for TPX and ITER. (author)

Fast commutation of high current in double wire array Z-pinch loads

International Nuclear Information System (INIS)

Davis, J.; Gondarenko, N.A.; Velikovich, A.L.

1997-01-01

A dynamic model of multi-MA current commutation in a double wire array Z-pinch load is proposed and studied theoretically. Initially, the load is configured as nested concentric wire arrays, with the current driven through the outer array and imploding it. Once the outer array or the annular plasma shell formed from it approaches the inner array, the imploded plasma might penetrate through the gaps between the wires, but the azimuthal magnetic field is trapped due to both the high conductivity of the inner wires and the inductive coupling between the two parts of the array, causing a rapid switching of the total current to the inner part of the array. copyright 1997 American Institute of Physics

Current drive with fast waves, electron cyclotron waves, and neutral injection in the DIII-D tokamak

International Nuclear Information System (INIS)

Prater, R.; Petty, C.C.; Pinsker, R.I.

1993-01-01

Current drive experiments have been performed on the DIII-D tokamak using fast waves, electron cyclotron waves, and neutral injection. Fast wave experiments were performed using a 4-strap antenna with 1 MW of power at 60 MHz. These experiments showed effective heating of electrons, with a global heating efficiency equivalent to that of neutral injection even when the single pass damping was calculated to be as small as 5%. The damping was probably due to the effect of multiple passes of the wave through the plasma. Fast wave current drive experiments were performed with a toroidally directional phasing of the antenna straps. Currents driven by fast wave current drive (FWCD) in the direction of the main plasma current of up to 100 kA were found, not including a calculated 40 kA of bootstrap current. Experiments with FWCD in the counter current direction showed little current drive. In both cases, changes in the sawtooth behavior and the internal inductance qualitatively support the measurement of FWCD. Experiments on electron cyclotron current drive have shown that 100 kA of current can be driven by 1 MW of power at 60 GHz. Calculations with a Fokker-Planck code show that electron cyclotron current drive (ECCD) can be well predicted when the effects of electron trapping and of the residual electric field are included. Experiments on driving current with neutral injection showed that effective current drive could be obtained and discharges with full current drive were demonstrated. Interestingly, all of these methods of current drive had about the same efficiency. (Author)

Current drive with fast waves, electron cyclotron waves, and neutral injection in the DIII-D tokamak

International Nuclear Information System (INIS)

Prater, R.; Petty, C.C.; Pinsker, R.I.; Chiu, S.C.; deGrassie, J.S.; Harvey, R.W.; Ikel, H.; Lin-Liu, Y.R.; Luce, T.C.; James, R.A.; Porkolab, M.; Baity, F.W.; Goulding, R.H.; Hoffmann, D.J.; Kawashima, H.; Trukhin, V.

1992-09-01

Current drive experiments have been performed on the DIII-D tokamak using fast waves, electron cyclotron waves, and neutral injection. Fast wave experiments were performed using a 4-strap antenna with 1 MW of power at 60 MHz. These experiments showed effective heating of electrons, with a global heating efficiency equivalent to that of neutral injection even when the single pass damping was calculated to be as small as 5%. The damping was probably due to the effect of multiple passes of the wave through the plasma. Fast wave current drive experiments were performed with a toroidally directional phasing of the antenna straps. Currents driven by fast wave current drive (FWCD) in the direction of the main plasma current of up to 100 kA were found, not including a calculated 40 kA of bootstrap current. Experiments with FWCD in the counter current direction showed little current drive. In both cases, changes in the sawtooth behavior and the internal inductance qualitatively support the measurement of FWCD. Experiments on electron cyclotron current drive have shown that 100 kA of current can be driven by 1 MW of power at 60 GHz. Calculations with a Fokker-Planck code show that electron cyclotron current drive (ECCD) can be well predicted when the effects of electron trapping and of the residual electric field are included. Experiments on driving current with neutral injection showed that effective current drive could be obtained and discharges with full current drive were demonstrated. Interestingly, all of these methods of current drive had about the same efficiency, 0.015 x 10 20 MA/MW/m 2

Estimation of post disruption plasma temperature for fast current quench Aditya plasma shots

International Nuclear Information System (INIS)

Purohit, S.; Chowdhuri, M.B.; Joisa, Y.S.; Raval, J.V.; Ghosh, J.; Jha, R.

2013-01-01

Characteristics of tokamak current quenches are an important issue for the determination of electromagnetic forces that act on the in-vessel components and vacuum vessel during major disruptions. It is observed that thermal quench is followed by a sharp current decay. Fast current quench disruptive plasma shots were investigated for ADITYA tokamak. The current decay time was determined for the selected shots, which were in the range of 0.8 msec to 2.5 msec. This current decay information was then applied to L/R model, frequently employed for the estimation of the current decay time in tokamak plasmas, considering plasma inductance and plasma resistivity. This methodology was adopted for the estimation of the post disruption plasma temperature using the experimentally observed current decay time for the fast current quench disruptive ADITYA plasma shots. The study reveals that for the identified shots there is a constant increase in the current decay time with the post disruption plasma temperature. The investigations also explore the behavior post disruption plasma temperature and the current decay time as a function of the edge safety factor, Q. Post disruption plasma temperature and the current decay time exhibits a decrease with the increase in the value Q. (author)

A dual-path, current-sensing resistor-free boost LED driver with fast PWM dimming

International Nuclear Information System (INIS)

Zhou Minchao; Lü Danzhu; Cheng Lin; Hong Zhiliang; Liu, Bill Yang

2013-01-01

A boost LED driver featuring a high PWM dimming ratio and optimized efficiency is presented. This LED driver, which has a low dropout voltage and is able to drive 3–7 LEDs in series with constant output current and fast PWM dimming, provides an alternative technique for brightness adjustment. A dual-path control scheme with automatic switching and state maintenance is proposed. Meanwhile, a cascode current mirror structure is applied with the output transistor multiplexed as an LED PWM dimming transistor. Implemented in 0.5 μm 25 V BCD process, the measurement results show that a voltage conversion range of 5 V input to 6–24 V output with constant output current is obtained. With automatically switching dual-path control and an optimized current mirror, the response time during PWM dimming is reduced to as low as 240 ns and the efficiency keeps above 89% over a wide PWM dimming ratio - 250 mA output current. (semiconductor integrated circuits)

Optimal spin current pattern for fast domain wall propagation in nanowires

Science.gov (United States)

Yan, Peng; Sun, Zhouzhou; Schliemann, John; Wang, Xiangrong

2011-03-01

One of the important issues in nanomagnetism is to lower the current needed for a technologically useful domain wall (DW) propagation speed. Based on the modified Landau-Lifshitz-Gilbert (LLG) equation with both Slonczewski spin-transfer torque and the field-like torque, we derive an optimal temporally and spatially varying spin current pattern for fast DW propagation along nanowires. Under such conditions, the DW velocity in biaxial wires can be enhanced as much as tens of times higher than that achieved in experiments so far. Moreover, the fast variation of spin polarization can efficiently help DW depinning. Possible experimental realizations are discussed. This work is supported by Hong Kong RGC grants (#603508, 604109, RPC10SC05 and HKU10/CRF/08-HKUST17/CRF/08), and by Deutsche Forschungsgemeinschaft via SFB 689. ZZS thanks the Alexander von Humboldt Foundation (Germany) for a grant.

Resistive current limiter with high-temperature superconductors. Final report

International Nuclear Information System (INIS)

Schubert, M.

1995-12-01

Fundamental results of the possibility of using high temperature superconductors (HTSC) in resistive fault current limiters are discussed. Measurement of the homogeneity of BSCCO-powder-in-tube materials were made. In addition, investigations of the transition from superconducting to normalconducting state under AC-current conditions were carried out. Based on these results, simulations of HTSC-materials on ceramic substrate were made and recent results are presented. Important results of the investigations are: 1. Current-limiting without external trigger only possible when the critical current density of HTSC exceeds 10 4 A/cm 2 . 2. Inhomogeneities sometimes cause problems with local destruction. This can be solved by parallel-elements or external trigger. 3. Fast current-limiting causes overvoltages which can be reduced by using parallel-elements. (orig.) [de

Design Considerations of Fast Kicker Systems for High Intensity Proton Accelerators

International Nuclear Information System (INIS)

Zhang, W.; Sandberg, J.; Parson, W.M.; Walstrom, P.; Murray, M.M.; Cook, E.; Hartouni, E.

2001-01-01

In this paper, we discuss the specific issues related to the design of the Fast Kicker Systems for high intensity proton accelerators. To address these issues in the preliminary design stage can be critical since the fast kicker systems affect the machine lattice structure and overall design parameters. Main topics include system architecture, design strategy, beam current coupling, grounding, end user cost vs. system cost, reliability, redundancy and flexibility. Operating experience with the Alternating Gradient Synchrotron injection and extraction kicker systems at Brookhaven National Laboratory and their future upgrade is presented. Additionally, new conceptual designs of the extraction kicker for the Spallation Neutron Source at Oak Ridge and the Advanced Hydrotest Facility at Los Alamos are discussed

Fast current amplifier for background-limited operation of photovoltaic InSb detectors

Energy Technology Data Exchange (ETDEWEB)

Altmann, J; Koehler, S; Lahmann, W

1981-01-01

A fast current amplifier for use with photovoltaic indium antimonide detectors is described which was designed for detection of lidar return signals. Near background-limited operation was possible for bandwidths up to 0.8 MHz.

Fast Reactive Power Sharing, Circulating Current and Resonance Suppression for Parallel Inverters Using Resistive-Capacitive Output Impedance

DEFF Research Database (Denmark)

Chen, Yandong; Guerrero, Josep M.; Shuai, Zhikang

2016-01-01

In this paper, an inverter using resistivecapacitive output impedance (RC-type inverter) is proposed not only to provide fast reactive power sharing to support microgrid voltage, and but also to reduce circulating currents and damp high-frequency resonances among inverters. Introducing the RC......-frequency resonances among parallel inverters are quantitatively analyzed. The control parameters are systematically selected, and effect of virtual complex impedance on the inverter output voltage is depicted. The RC-type inverter can reduce circulating currents and damp resonances due to different equivalent output...

Fast prototyping of conducting polymer microelectrodes using resistance-controlled high precision drilling

DEFF Research Database (Denmark)

Kafka, Jan Robert; Geschke, Oliver; Skaarup, Steen

2011-01-01

We present a straightforward method for fast prototyping of microelectrode arrays in the highly conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT). Microelectrode arrays were produced by electrical resistance-controlled microdrilling through an insulating polymer layer (TOPAS® 5013...... approach the steady state currents predicted from modeling, but at a much slower rate than expected. This is shown to be caused by the use of electroactive PEDOT electrodes. Subtraction of the latter contribution gives approach to steady state currents within a few seconds, which is in very good agreement...

Local magnetic shear control in a tokamak via fast wave minority ion current drive: Theory and experiments in JET

International Nuclear Information System (INIS)

Bhatnagar, V.P.; Start, D.F.H.; Jacquinot, J.; Chaland, F.; Cherubini, A.; Porcelli, F.

1994-01-01

When an ion cyclotron resonance heating (ICRH) antenna array is phased (Δ Φ ≠ 0 or π), the excited asymmetric k parallel spectrum can drive non-inductive currents by interaction of fast waves both with electrons (transit time magnetic pumping (e-TTMP) and Landau damping (e-LD)) and with ions at minority (fundamental) or harmonic cyclotron resonances, depending upon the scenario. On the basis of earlier theories, a simplified description is presented that includes the minority ion and electron current drive effects simultaneously in a 3-D ray tracing calculation in the tokamak geometry. The experimental results of sawtooth stabilization or destabilization in JET using the minority ion current drive scheme are presented. This scheme allows a modification of the local current density gradient (or the magnetic shear) at the q = 1 surface resulting in a control of a sawteeth. The predictions of the above model of current drive and its effects on sawtooth period calculated in conjunction with a model of stability of internal resistive kink modes, that encompasses the effects of both the fast particle pressure and the local (q = 1) magnetic shear, are found to be qualitatively in good agreement with the experimental results. Further, the results are discussed of our model of fast wave current drive scenarios of magnetic shear reversal with a view to achieving long duration high confinement regimes in the forthcoming experimental campaign on JET. Finally, the results are presented of minority current drive for sawtooth control in next step devices such as the International Thermonuclear Experimental Reactor (ITER). (author). 44 refs, 23 figs, 3 tabs

Effect of Fast Neutron Irradiation on Current Transport Properties of HTS Materials

CERN Document Server

Ballarino, A; Kruglov, V S; Latushkin, S T; Lubimov, A N; Ryazanov, A I; Shavkin, S V; Taylor, T M; Volkov, P V

2004-01-01

The effect of fast neutron irradiation with energy up to 35 MeV and integrated fluence of up to 5 x 10**15 cm-2 on the current transport properties of HTS materials Bi-2212 and Bi-2223 has been studied, both at liquid nitrogen and at room temperatures. The samples irradiated were selected after verification of the stability of their superconducting properties after temperature cycling in the range of 77 K - 293 K. It has been found that the irradiation by fast neutrons up to the above dose does not produce a significant degradation of critical current. The effect of room temperature annealing on the recovery of transport properties of the irradiated samples is also reported, as is a preliminary microstructure investigation of the effect of irradiation on the soldered contacts.

Effect of coupling currents on the dynamic inductance during fast transient in superconducting magnets

Directory of Open Access Journals (Sweden)

V. Marinozzi

2015-03-01

Full Text Available We present electromagnetic models aiming to calculate the variation of the inductance in a magnet due to dynamic effects such as the variation of magnetization or the coupling with eddy currents. The models are studied with special regard to the calculation of the inductance in superconducting magnets which are affected by interfilament coupling currents. The developed models have been compared with experimental data coming from tests of prototype Nb_{3}Sn magnets designed for the new generation of accelerators. This work is relevant for the quench protection study of superconducting magnets: quench is an unwanted event, when part of the magnet becomes resistive; in these cases, the current should be discharged as fast as possible, in order to maintain the resistive zone temperature under a safe limit. The magnet inductance is therefore a relevant term for the description of the current discharge, especially for the high-field new generation superconducting magnets for accelerators, and this work shows how to calculate the correct value during rapid current changes, providing a mean for simulations of the reached temperature.

Fast Food Consumption Behaviors in High-School Students based on the Theory of Planned Behavior (TPB

Directory of Open Access Journals (Sweden)

Kamal Mirkarimi

2016-07-01

Full Text Available Background: Studies report inappropriate snack and junk food consumption patterns in children and young adults in Iran. The current survey was aimed to explore fast food consumption behaviors in high-school students based on the Theory of Planned Behavior. Materials and Methods: A cross-sectional study was done among 500 high-school students. Samples were selected based on cluster sampling method at first and simple random at second. Data were collected using a researcher-made questionnaire. To analyze, SPSS-16 and tests, including t-test, Chi-square, correlation coefficient and multiple regressions were used. Results: The monthly frequency of fast food consumption was 4.01. The TPB explained fast food use behaviors with R2 of 0.6, effectively. Results also represented that frequency of fast food consumption was meaningfully in line with behavioral intention (β = 0.60, P < 0.05 and subjective norms (β = 0.17, P < 0.05. Conclusion: It seems likely beneficial to consider important subjective norms (especially friends that may strongly effect on high-school student intention to use fast food. Also students perceived behavioral control must be increased.

Photon-trapping micro/nanostructures for high linearity in ultra-fast photodiodes

Science.gov (United States)

Cansizoglu, Hilal; Gao, Yang; Perez, Cesar Bartolo; Ghandiparsi, Soroush; Ponizovskaya Devine, Ekaterina; Cansizoglu, Mehmet F.; Yamada, Toshishige; Elrefaie, Aly F.; Wang, Shih-Yuan; Islam, M. Saif

2017-08-01

Photodetectors (PDs) in datacom and computer networks where the link length is up to 300 m, need to handle higher than typical input power used in other communication links. Also, to reduce power consumption due to equalization at high speed (>25Gb/s), the datacom links will use PAM-4 signaling instead of NRZ with stringent receiver linearity requirements. Si PDs with photon-trapping micro/nanostructures are shown to have high linearity in output current verses input optical power. Though there is less silicon material due to the holes, the micro-/nanostructured holes collectively reradiate the light to an in-plane direction of the PD surface and can avoid current crowding in the PD. Consequently, the photocurrent per unit volume remains at a low level contributing to high linearity in the photocurrent. We present the effect of design and lattice patterns of micro/nanostructures on the linearity of ultra-fast silicon PDs designed for high speed multi gigabit data networks.

High-definition velocity-space tomography of fast-ion dynamics

DEFF Research Database (Denmark)

Salewski, Mirko; Geiger, B.; Jacobsen, A.S.

2016-01-01

Velocity-space tomography of the fast-ion distribution function in a fusion plasma is usually a photon-starved tomography method due to limited optical access and signal-to-noise ratio of fast-ion Dα (FIDA) spectroscopy as well as the strive for high-resolution images. In high-definition tomography...... information to reconstruct where in velocity space the measurements and the simulation disagree. This alternative approach is demonstrated for four-view as well as for two-view FIDA measurements. The high-definition tomography tools allow us to study fast ions in sawtoothing plasmas and the formation of NBI...

The Impact of Beam Deposition on Bootstrap Current of Fast Ion Produced by Neutral Beam Tangential Injection

International Nuclear Information System (INIS)

Huang Qian-Hong; Gong Xue-Yu; Lu Xing-Qiang; Yu Jun; Cao Jin-Jia

2015-01-01

The density profile of fast ions arising from a tangentially injected diffuse neutral beam in tokamak plasma is calculated. The effects of mean free paths and beam tangency radius on the density profile are discussed under typical HL-2A plasmas parameters. The results show that the profile of fast ions is strongly peaked at the center of the plasma when the mean free path at the maximum deuteron density is larger than the minor radius, while the peak value decreases when the mean free path at the maximum deuteron density is larger than twice that of the minor radius due to the beam transmission loss. Moreover, the bootstrap current of fast ions for various mean free paths at the maximum deuteron density is calculated and its density is proved to be closely related to the deposition of the neutral beam. With the electron return current considered, the net current density obviously decreases. Meanwhile, the peak central fast ion density increases when the beam tangency radius approaches the major radius, and the net bootstrap current increases rapidly with the increasing beam tangency radius. (paper)

Potentiality of fast wave current drive in non-maxwellian plasmas

International Nuclear Information System (INIS)

Moreau, D.; O'Brien, M.R.; Cox, M.; Start, D.F.H.

1987-06-01

After a short analysis of the available experimental data on pure fast wave electron current drive we propose a theoretical scaling law for the wave absorption through combined electron Landau damping and transit time magnetic pumping. We then present the result of a fully relativistic calculation which we apply to a bi-Maxwellian electron distribution function and conclude on the requirements to be fulfilled by the energetic tail for obtaining significant damping in Tore-Supra

A 3 A sink/source current fast transient response low-dropout Gm driven linear regulator

International Nuclear Information System (INIS)

Chu Xiuqin; Li Qingwei; Lai Xinquan; Yuan Bing; Li Yanming; Zhao Yongrui

2011-01-01

A 3 A sink/source G m -driven CMOS low-dropout regulator (LDO), specially designed for low input voltage and low cost, is presented by utilizing the structure of a current mirror G m (transconductance) driving technique, which provides high stability as well as a fast load transient response. The proposed LDO was fabricated by a 0.5 μm standard CMOS process, and the die size is as small as 1.0 mm 2 . The proposed LDO dissipates 220 μA of quiescent current in no-load conditions and is able to deliver up to 3 A of load current. The measured results show that the output voltage can be resumed within 2 μs with a less than 1 mV overshoot and undershoot in the output current step from -1.8 to 1.8 A with a 0.1 μs rising and falling time at three 10 μF ceramic capacitors. (semiconductor integrated circuits)

First results on fast wave current drive in advanced tokamak discharges in DIII-D

International Nuclear Information System (INIS)

Prater, R.; Cary, W.P.; Baity, F.W.

1995-07-01

Initial experiments have been performed on the DIII-D tokamak on coupling, direct electron heating, and current drive by fast waves in advanced tokamak discharges. These experiments showed efficient central heating and current drive in agreement with theory in magnitude and profile. Extrapolating these results to temperature characteristic of a power plant (25 keV) gives current drive efficiency of about 0.3 MA/m 2

High-burn-up fuels for fast reactors. Past experience and novel applications

International Nuclear Information System (INIS)

Weaver, Kevan D.; Gilleland, John; Whitmer, Charles; Zimmerman, George

2009-01-01

Fast reactors in the U.S. routinely achieved fuel burn-ups of 10%, with some fuel able to reach peak burn-ups of 20%, notably in the Experimental Breeder Reactor II and the Fast Flux Test Facility. Maximum burn-up has historically been constrained by chemical and mechanical interactions between the fuel and its cladding, and to some extent by radiation damage and thermal effects (e.g., radiation-induced creep, thermal creep, and radiation embrittlement) that cause the cladding to weaken. Although fast reactors have used several kinds of fuel - including oxide, metal alloy, carbide, and nitride - the vast majority of experience with fast reactors has been using oxide (including mixed oxide) and metal-alloy fuels based on uranium. Our understanding of high-burn-up operation is also limited by the fact that breeder reactor programs have historically assumed that their fuel would eventually undergo reprocessing; the programs thus have not made high burn-up a top priority. Recently a set of novel designs have emerged for fast reactors that require little initial enrichment and no reprocessing. These reactors exploit a concept known as a traveling wave (sometimes referred to as a breed-and-burn wave, fission wave, or nuclear-burning wave). By breeding and using its own fuel in place as it operates, a traveling-wave reactor can obtain burn-ups that approach 50%, well beyond the current base of knowledge and experience. Our computational work on the physics of traveling-wave reactors shows that they require metal-alloy fuel to provide the margins of reactivity necessary to sustain a breed-and-burn wave. This paper reviews operating experience with high-burn-up fuels and the technical feasibility of moving to a qualitatively new burn-up regime. We discuss our calculations on traveling-wave reactors, including those concerning the possible use of thorium. The challenges associated with high burn-up and fluence in fuels and materials are also discussed. (author)

A HIGH BANDWIDTH BIPOLAR POWER SUPPLY FOR THE FAST CORRECTORS IN THE APS UPGRADE*

Energy Technology Data Exchange (ETDEWEB)

Wang, Ju; Sprau, Gary

2017-06-25

The APS Upgrade of a multi-bend achromat (MBA) storage ring requires a fast bipolar power supply for the fast correction magnets. The key performance requirement of the power supply includes a small-signal bandwidth of 10 kHz for the output current. This requirement presents a challenge to the design because of the high inductance of the magnet load and a limited input DC voltage. A prototype DC/DC power supply utilizing a MOSFET H-bridge circuit with a 500 kHz PWM has been developed and tested successfully. The prototype achieved a 10-kHz bandwidth with less than 3-dB attenuation for a signal 0.5% of the maximum operating current of 15 amperes. This paper presents the design of the power circuit, the PWM method, the control loop, and the test results.

High frequency fast wave results from the CDX-U spherical torus

International Nuclear Information System (INIS)

Kaita, R.; Majeski, R.; Menard, J.

2001-01-01

The Current Drive Experiment-Upgrade (CDX-U) is the first spherical torus (ST) to investigate radio frequency (RF) heating and current drive. To address the concern that large magnetic field line pitch at the outboard midplane of ST's could inhibit successful coupling to the high harmonic fast wave (HHFW), a rotatable, two strap antenna was installed on CDX-U. Parasitic loading and impurity generation were discovered to be weak and nearly independent of antenna phasing and angle over a wide range, and fast wave electron heating has been observed. Plasma densities up to about 10 12 cm -3 were obtained with noninductive startup solely with HHFW. New ST diagnostics under development on CDX-U include a multilayer mirror (MLM) detector to measure ultrasoft X-rays, a twelve spatial point Thomson scattering (TS) system, and an Electron Bernstein Wave (EBW) system for both electron heating and electron temperature measurements. Preliminary experiments with a boron low velocity edge micropellet injector have also been performed, and further studies of its effectiveness for impurity control will be conducted with a variety of spectroscopic and imaging diagnostics on CDX-U. (author)

High frequency fast wave results from the CDX-U spherical torus

International Nuclear Information System (INIS)

Kaita, R.; Majeski, R.; Menard, J.

1999-01-01

The Current Drive Experiment-Upgrade (CDX-U) is the first spherical torus (ST) to investigate radio frequency (RF) heating and current drive. To address the concern that large magnetic field line pitch at the outboard midplane of ST's could inhibit successful coupling to the high harmonic fast wave (HHFW), a rotatable, two strap antenna was installed on CDX-U. Parasitic loading and impurity generation were discovered to be weak and nearly independent of antenna phasing and angle over a wide range, and fast wave electron heating has been observed. Plasma densities up to about 10 12 cm -3 were obtained with noninductive startup solely with HHFW. New ST diagnostics under development on CDX-U include a multilayer mirror (MLM) detector to measure ultrasoft X-rays, a twelve spatial point Thomson scattering (TS) system, and an Electron Bernstein Wave (EBW) system for both electron heating and electron temperature measurements. Preliminary experiments with a boron low velocity edge micropellet injector have also been performed, and further studies of its effectiveness for impurity control will be conducted with a variety of spectroscopic and imaging diagnostics on CDX-U. (author)

Current design efforts for the gas-cooled fast reactor (GFR)

International Nuclear Information System (INIS)

Weaver, K.D.

2005-01-01

Current research and development on the Gas-Cooled Fast Reactor (GCFR) has focused on the design of safety systems that will remove the decay heat during accident conditions, ion irradiations of candidate ceramic materials, joining studies of oxide dispersion strengthened alloys; and within the Advanced Fuel Cycle Initiative (AFC I) the fabrication of carbide fuels and ceramic fuel matrix materials, development of non-halide precursor low density and high density ceramic coatings, and neutron irradiation of candidate ceramic fuel matrix and metallic materials. The vast majority of this work has focused on the reference design for the GCFR: a helium-cooled, direct Brayton cycle power conversion system that will operate with an outlet temperature of 850 C at 7 MPa. In addition to the work being performed in the United States, seven international partners under the Generation IV International Forum (GIF) have identified their interest in participating in research related to the development of the GCFR. These are EURATOM (European Commission), France, Japan, South Africa, South Korea, Switzerland, and the United Kingdom. Of these, EURATOM (including the United Kingdom), France, Japan, and Switzerland have active research activities with respect to the GCFR. The research includes GCFR design and safety, and fuels/in-core materials/fuel cycle projects. This paper outlines the current design status of the GCFR, and includes work done in the areas mentioned above. (Author)

Study of fast wave current drive in a KT-2 tokamak plasma

International Nuclear Information System (INIS)

Hong, B.G.; Hamamatsu, Kiyotaka

1996-02-01

Global analysis of fast wave current drive in a KT-2 tokamak plasma is performed by using the code, TASKW1, developed by JAERI and Okayama University (Dr. Fukuyama), which solves the kinetic wave equation in a one dimensional slab geometry. A phase-shifted antenna array is used to inject toroidal momentum to electrons. To find guidelines of optimum antenna design for efficient current drive, accessibility conditions are derived. The dependence of the current drive efficiency on launching conditions such as the total number of antennas, phase and spacing is investigated for two cases of wave frequency; f=30 MHz ( cH ) and f=225 MHz (=5f cH ). (author)

High-ampacity conductive polymer microfibers as fast response wearable heaters and electromechanical actuators

KAUST Repository

Zhou, Jian; Mulle, Matthieu; Zhang, Yaobin; Xu, Xuezhu; Li, Erqiang; Han, Fei; Thoroddsen, Sigurdur T; Lubineau, Gilles

2016-01-01

Conductive fibers with enhanced physical properties and functionalities are needed for a diversity of electronic devices. Here, we report very high performance in the thermal and mechanical response of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) microfibers when subjected to an electrical current. These fibers were made by combining the hot-drawing assisted wetspinning process with ethylene glycol doping/de-doping that can work at a current density as high as 1.8 × 104 A cm−2, which is comparable to that of carbon nanotube fibers. Their electrothermal response was investigated using optical sensors and verified to be as fast as 63 °C s−1 and is comparable with that of metallic heating elements (20–50 °C s−1). We investigated the electromechanical actuation resulted from the reversible sorption/desorption of moisture controlled by electro-induced heating. The results revealed an improvement of several orders of magnitudes compared to other linear conductive polymer-based actuators in air. Specifically, the fibers we designed here have a rapid stress generation rate (>40 MPa s−1) and a wide operating frequency range (up to 40 Hz). These fibers have several characteristics including fast response, low-driven voltage, good repeatability, long cycle life and high energy efficiency, favoring their use as heating elements on wearable textiles and as artificial muscles for robotics.

High-ampacity conductive polymer microfibers as fast response wearable heaters and electromechanical actuators

KAUST Repository

Zhou, Jian

2016-01-04

Conductive fibers with enhanced physical properties and functionalities are needed for a diversity of electronic devices. Here, we report very high performance in the thermal and mechanical response of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) microfibers when subjected to an electrical current. These fibers were made by combining the hot-drawing assisted wetspinning process with ethylene glycol doping/de-doping that can work at a current density as high as 1.8 × 104 A cm−2, which is comparable to that of carbon nanotube fibers. Their electrothermal response was investigated using optical sensors and verified to be as fast as 63 °C s−1 and is comparable with that of metallic heating elements (20–50 °C s−1). We investigated the electromechanical actuation resulted from the reversible sorption/desorption of moisture controlled by electro-induced heating. The results revealed an improvement of several orders of magnitudes compared to other linear conductive polymer-based actuators in air. Specifically, the fibers we designed here have a rapid stress generation rate (>40 MPa s−1) and a wide operating frequency range (up to 40 Hz). These fibers have several characteristics including fast response, low-driven voltage, good repeatability, long cycle life and high energy efficiency, favoring their use as heating elements on wearable textiles and as artificial muscles for robotics.

A design study of high electric power for fast reactor cooled by supercritical light water

International Nuclear Information System (INIS)

Koshizuka, Seiichi

2000-03-01

In order to evaluate the possibility to achieve high electric power by a fast reactor with supercritical light water, the design study was carried out on a large fast reactor core with high coolant outlet temperature (SCFR-H). Since the reactor coolant circuit uses once-through direct cycle where all feedwater flows through the core to the turbine at supercritical pressure, it is possible to design much simpler and more compact reactor systems and to achieve higher thermal efficiency than those of current light water reactors. The once-through direct cycle system is employed in current fossil-fired power plants. In the present study, three types of core were designed. The first is SCFR-H with blankets cooled by ascending flow, the second is SCFR-H with blankets cooled by descending flow and the third is SCFR-H with high thermal power. Every core was designed to achieve the thermal efficiency over 43%, positive coolant density reactivity coefficient and electric power over 1600 MW. Core characteristics of SCFR-Hs were compared with those of SCLWR-H (electric power: 1212 MW), which is a thermal neutron spectrum reactor cooled and moderated by supercritical light water, with the same diameter of the reactor pressure vessel. It was shown that SCFR-H could increase the electric power about 1.7 times maximally. From the standpoint of the increase of a reactor thermal power, a fast reactor has advantages as compared with a thermal neutron reactor, because it can increase the power density by adopting tight fuel lattices and eliminating the moderator region. Thus, it was concluded that a reactor cooled by supercritical light water could further improve the cost competitiveness by using a fast neutron spectrum and achieving a higher thermal power. (author)

Onset of fast "ideal" tearing in thin current sheets: Dependence on the equilibrium current profile

Science.gov (United States)

Pucci, F.; Velli, M.; Tenerani, A.; Del Sarto, D.

2018-03-01

In this paper, we study the scaling relations for the triggering of the fast, or "ideal," tearing instability starting from equilibrium configurations relevant to astrophysical as well as laboratory plasmas that differ from the simple Harris current sheet configuration. We present the linear tearing instability analysis for equilibrium magnetic fields which (a) go to zero at the boundary of the domain and (b) contain a double current sheet system (the latter previously studied as a Cartesian proxy for the m = 1 kink mode in cylindrical plasmas). More generally, we discuss the critical aspect ratio scalings at which the growth rates become independent of the Lundquist number S, in terms of the dependence of the Δ' parameter on the wavenumber k of unstable modes. The scaling Δ'(k) with k at small k is found to categorize different equilibria broadly: the critical aspect ratios may be even smaller than L/a ˜ Sα with α = 1/3 originally found for the Harris current sheet, but there exists a general lower bound α ≥ 1/4.

Effects of a longitudinal magnetic field on current pulses and fast ionization-wave structure

International Nuclear Information System (INIS)

Asinovskii, E.I.; Lagar'kov, A.N.; Markovets, V.V.; Rutkevich, I.M.; Ul'yanov, A.M.; Filyugin, I.V.

1988-01-01

A longitudinal magnetic field affects the fast ionization-wave structure in a discharge tube surrounded by a metal screen. The field does not alter the wave speed, but the current amplitude is increased. This is explained from a theory for fast-wave propagation in a cylindrical guide containing an axial field. Numerical solutions have been obtained for the stationary nonlinear waves, which are compared with measurements. A theoretical study has been made on the ionization-wave features for large values of the Hall parameter

A formula for efficiency of fast wave current drive in fusion devices

International Nuclear Information System (INIS)

Chiu, S.C.; Harvey, R.W.; Karney, C.F.F.; Mau, T.K.

1992-06-01

Fast wave current drive (FWCD) is a principal candidate for non- inductive current drive schemes in reactors. Major experiments are in progress or planned on DIII-D, JET, and Tore-Supra. A theory for FWCD was presented by two of the authors and collaborators. To minimize computations required in transport simulations, and for analytical understanding, it is very useful to have a concise analytical efficiency formula. Fisch and Karney, and Ehst and Karney have obtained empirical formulae that fits numerical results for the Landau limit and Alfven limit; the latter fits results at 1 i ≤ 2. This paper extends a previous numerical study on FWCD at arbitrary frequencies and Z i . Analytical formulae for FWCD efficiency, valid for all frequencies and Z i , are derived using the adjoint technique in high and low phase velocity regions. A smooth patching between the two regions produces an analytical formula which is accurate for all frequencies, Z i , and phase velocities. Comparison with existing results will be discussed. A corollary of the present calculation is that a low phase velocities and in the Landau limit, the efficiency is the same as that calculated from the Lorentz model collision operator

Calculation of the non-inductive current profile in high-performance NSTX plasmas

Science.gov (United States)

Gerhardt, S. P.; Fredrickson, E.; Gates, D.; Kaye, S.; Menard, J.; Bell, M. G.; Bell, R. E.; Le Blanc, B. P.; Kugel, H.; Sabbagh, S. A.; Yuh, H.

2011-03-01

The constituents of the current profile have been computed for a wide range of high-performance plasmas in NSTX (Ono et al 2000 Nucl. Fusion 40 557); these include cases designed to maximize the non-inductive fraction, pulse length, toroidal-β or stored energy. In the absence of low-frequency MHD activity, good agreement is found between the reconstructed current profile and that predicted by summing the independently calculated inductive, pressure-driven and neutral beam currents, without the need to invoke any anomalous beam ion diffusion. Exceptions occur, for instance, when there are toroidal Alfvén eigenmode avalanches or coupled m/n = 1/1 + 2/1 kink-tearing modes. In these cases, the addition of a spatially and temporally dependent fast-ion diffusivity can reduce the core beam current drive, restoring agreement between the reconstructed profile and the summed constituents, as well as bringing better agreement between the simulated and measured neutron emission rate. An upper bound on the fast-ion diffusivity of ~0.5-1 m2 s-1 is found in 'MHD-free' discharges, based on the neutron emission, the time rate of change in the neutron signal when a neutral beam is stepped and reconstructed on-axis current density.

Calculation of the Non-Inductive Current Profile in High-Performance NSTX Plasmas

International Nuclear Information System (INIS)

Gerhardt, S.P.; Fredrickson, E.; Gates, D.; Kaye, S.; Menard, J.; Bell, M.G.; Bell, R.E.; Le Blanc, B.P.; Kugel, H.; Sabbagh, S.A.; Yuh, H.

2011-01-01

The constituents of the current profile have been computed for a wide range of high-performance plasmas in NSTX [M. Ono, et al., Nuclear Fusion 40, 557 (2000)]; these include cases designed to maximize the non-inductive fraction, pulse length, toroidal-β, or stored energy. In the absence of low-frequency MHD activity, good agreement is found between the reconstructed current profile and that predicted by summing the independently calculated inductive, pressure-driven, and neutral beam currents, without the need to invoke any anomalous beam ion diffusion. Exceptions occur, for instance, when there are toroidal Alfven eigenmode avalanches or coupled m/n=1/1+2/1 kink-tearing modes. In these cases, the addition of a spatially and temporally dependent fast ion diffusivity can reduce the core beam current drive, restoring agreement between the reconstructed profile and the summed constituents, as well as bringing better agreement between the simulated and measured neutron emission rate. An upper bound on the fast ion diffusivity of ∼0.5-1 m 2 /sec is found in 'MHD-free' discharges, based on the neutron emission, time rate of change of the neutron signal when a neutral beam is stepped, and reconstructed on-axis current density.

Los Alamos Compact Toroid, fast liner, and High-Density Z-Pinch programs

International Nuclear Information System (INIS)

Linford, R.K.; Hammel, J.E.; Sherwood, H.R.

1982-01-01

The compact Toroid and High Density Z-Pinch are two of the plasma configurations presently being studied at Los Alamos. This paper summarizes these two programs along with the recently terminated Fast Liner Program. Included in this discussion is an analysis of compact Toroid formation techniques showing the tearing and reconnection of the fields that separate the spheromak from the radial fields of the coaxial source, and the final equilibrium state of the elongated FRC in the theta-pinch coil. In addition the typical dimensions of the geometry of the Fast Liner experiments are delineated Z-pinch and electrode assembly is displayed as is a graphic of the temporal behavior of the current required for radial equilibrium. Spheromak is examined in terms of formation, gross stability, and equilibrium and field reversed configuration is discussed in terms of gross stability, equilibrium, and confinement scaling

An investigation of the field-aligned currents associated with a large-scale ULF wave using data from CUTLASS and FAST

Directory of Open Access Journals (Sweden)

H. C. Scoffield

2005-02-01

Full Text Available On 14 December 1999, a large-scale ULF wave event was observed by the Hankasalmi radar of the SuperDARN chain. Simultaneously, the FAST satellite passed through the Hankasalmi field-of-view, measuring the magnetic field oscillations of the wave at around 2000km altitude, along with the precipitating ion and electron populations associated with these fields. A simple field line resonance model of the wave has been created and scaled using the wave's spatial and temporal characteristics inferred from SuperDARN and IMAGE magnetometer data. Here the model calculated field-aligned current is compared with field-aligned currents derived from the FAST energetic particle spectra and magnetic field measurements. This comparison reveals the small-scale structuring and energies of the current carriers in a large-scale Alfvén wave, a topic, which at present, is of considerable theoretical interest. When FAST traverses a region of the wave involving low upward field-aligned current densities, the current appears to be carried by unstructured downgoing electrons of energies less than 30eV. A downward current region appears to be carried partially by upgoing electrons below the FAST energy detection threshold, but also consists of a mixture of hotter downgoing magnetospheric electrons and upgoing ionospheric electrons of energies <30eV, with the hotter upgoing electrons presumably representing those upgoing electrons which have been accelerated by the wave field above the low energy detection threshold of FAST. A stronger interval of upward current shows that small-scale structuring of scale ~50km has been imposed on the current carriers, which are downgoing magnetospheric electrons of energy 0-500eV.

Very Fast Current Diagnostic for Linear Pulsed Beams

Directory of Open Access Journals (Sweden)

Nassisi Vincenzo

2018-01-01

Full Text Available Fast current pulses manage lasers and particle accelerators and require sophisticate systems to be detected. At today Rogowski coils are well known. They are designed and built with a toroidal structure. In recently application, flat transmission lines are imploded and for this reason we develop a linear Rogowski coil to detect current pulses inside flat conductors. To get deep information from the system, it was approached by means of the theory of the transmission lines. The coil we build presents a resistance but it doesn’t influence the rise time of the response, instead the integrating time. We also studied the influence of the magnetic properties of coil support. The new device was able to record pulses of more hundred nanoseconds depending on the inductance, load impedance and resistance of the coil. Furthermore, its response was characterized by a sub-nanosecond rise time (~100 ps, The attenuation coefficient depends mainly on the turn number of the coil, while the quality of the response depends both on the manufacture quality of the coil and on the magnetic core characteristics. In biophysical applications often, a double line is employed in order to have a sample as control and a sample stressed by a light source. So, in this case we build two equal plane lines by 100 Ω characteristic resistance connected in parallel. We diagnosed the current present in a line. The attenuation factor resulted to be 11,5 A/V.

Very Fast Current Diagnostic for Linear Pulsed Beams

Science.gov (United States)

Nassisi, Vincenzo; Delle Side, Domenico; Turco, Vito

2018-01-01

Fast current pulses manage lasers and particle accelerators and require sophisticate systems to be detected. At today Rogowski coils are well known. They are designed and built with a toroidal structure. In recently application, flat transmission lines are imploded and for this reason we develop a linear Rogowski coil to detect current pulses inside flat conductors. To get deep information from the system, it was approached by means of the theory of the transmission lines. The coil we build presents a resistance but it doesn't influence the rise time of the response, instead the integrating time. We also studied the influence of the magnetic properties of coil support. The new device was able to record pulses of more hundred nanoseconds depending on the inductance, load impedance and resistance of the coil. Furthermore, its response was characterized by a sub-nanosecond rise time ( 100 ps), The attenuation coefficient depends mainly on the turn number of the coil, while the quality of the response depends both on the manufacture quality of the coil and on the magnetic core characteristics. In biophysical applications often, a double line is employed in order to have a sample as control and a sample stressed by a light source. So, in this case we build two equal plane lines by 100 Ω characteristic resistance connected in parallel. We diagnosed the current present in a line. The attenuation factor resulted to be 11,5 A/V.

High Hydrogen Content Graphene Hydride Compounds & High Cross-Section Cladding Coatings for Fast Neutron Detection

International Nuclear Information System (INIS)

Chandrashekhar, MVS

2017-01-01

The objective is to develop and implement a superior low-cost, large area (potentially >32in), easily deployable, close proximity, harsh environment innovative neutron sensor needed for next generation fuel cycle monitoring. We will exploit recent breakthroughs at the PI's lab on the electrochemistry of epitaxial graphene (EG) formed on commercial SiC wafers, a transformative nanomaterial system with superior radiation detection and durability properties to develop a new paradigm in detection for fast neutrons, a by-product of fission reactors. There are currently few effective detection/monitoring schemes, especially solid-state ones at present. This is essential for monitoring and control of future fuel cycles to make them more efficient and reliable. By exploiting these novel materials, as well as innovative hybrid SiC/EG/Cladding device architectures conceived by the team, will develop low-cost, high performance solutions to fast-neutron detection. Finally, we will also explore 3-terminal device implementations for neutron detectors with built-in electronic gain to further shrink these devices and improve their sensitivity.

Exploration of High Harmonic Fast Wave Heating on the National Spherical Torus Experiment

International Nuclear Information System (INIS)

Wilson, J.R.; Bell, R.E.; Bernabei, S.; Bitter, M.; Bonoli, P.; Gates, D.; Hosea, J.; LeBlanc, B.; Mau, T.K.; Medley, S.; Menard, J.; Mueller, D.; Ono, M.; Phillips, C.K.; Pinsker, R.I.; Raman, R.; Rosenberg, A.; Ryan, P.; Sabbagh, S.; Stutman, D.; Swain, D.; Takase, Y.; Wilgen, J.

2003-01-01

High Harmonic Fast Wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high-beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [Ono, M., Kaye, S.M., Neumeyer, S., et al., Proceedings, 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999, (IEEE, Piscataway, NJ (1999), p. 53.)] is such a device. An radio-frequency (rf) heating system has been installed on NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the ST concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode (high-confinement mode) discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge

A HIGH CURRENT, HIGH VOLTAGE SOLID-STATE PULSE GENERATOR FOR THE NIF PLASMA ELECTRODE POCKELS CELL

International Nuclear Information System (INIS)

Arnold, P A; Barbosa, F; Cook, E G; Hickman, B C; Akana, G L; Brooksby, C A

2007-01-01

A high current, high voltage, all solid-state pulse modulator has been developed for use in the Plasma Electrode Pockels Cell (PEPC) subsystem in the National Ignition Facility. The MOSFET-switched pulse generator, designed to be a more capable plug-in replacement for the thyratron-switched units currently deployed in NIF, offers unprecedented capabilities including burst-mode operation, pulse width agility and a steady-state pulse repetition frequency exceeding 1 Hz. Capable of delivering requisite fast risetime, 17 kV flattop pulses into a 6 (Omega) load, the pulser employs a modular architecture characteristic of the inductive adder technology, pioneered at LLNL for use in acceleration applications, which keeps primary voltages low (and well within the capabilities of existing FET technology), reduces fabrication costs and is amenable to rapid assembly and quick field repairs

A 3 A sink/source current fast transient response low-dropout G{sub m} driven linear regulator

Energy Technology Data Exchange (ETDEWEB)

Chu Xiuqin; Li Qingwei; Lai Xinquan; Yuan Bing [Institute of Electronic CAD, Xidian University, Xi' an 710071 (China); Li Yanming [School of Electronic and Control Engineering, Chang' an University, Xi' an 710064 (China); Zhao Yongrui, E-mail: liqw309@163.com, E-mail: xqchu@mail.xidian.edu.cn [Key Laboratory of High-Speed Circuit Design and EMC, Ministry of Education, Xidian University, Xi' an 710071 (China)

2011-06-15

A 3 A sink/source G{sub m}-driven CMOS low-dropout regulator (LDO), specially designed for low input voltage and low cost, is presented by utilizing the structure of a current mirror G{sub m} (transconductance) driving technique, which provides high stability as well as a fast load transient response. The proposed LDO was fabricated by a 0.5 {mu}m standard CMOS process, and the die size is as small as 1.0 mm{sup 2}. The proposed LDO dissipates 220 {mu}A of quiescent current in no-load conditions and is able to deliver up to 3 A of load current. The measured results show that the output voltage can be resumed within 2 {mu}s with a less than 1 mV overshoot and undershoot in the output current step from -1.8 to 1.8 A with a 0.1 {mu}s rising and falling time at three 10 {mu}F ceramic capacitors. (semiconductor integrated circuits)

Fast damping in mismatched high intensity beam transportation

Directory of Open Access Journals (Sweden)

V. Variale

2001-08-01

Full Text Available A very fast damping of beam envelope oscillation amplitudes was recently observed in simulations of high intensity beam transport, through periodic FODO cells, in mismatched conditions [V. Variale, Nuovo Cimento Soc. Ital. Fis. 112A, 1571–1582 (1999 and T. Clauser et al., in Proceedings of the Particle Accelerator Conference, New York, 1999 (IEEE, Piscataway, NJ, 1999, p. 1779]. A Landau damping mechanism was proposed at the origin of observed effect. In this paper, to further investigate the source of this fast damping, extensive simulations have been carried out. The results presented here support the interpretation of the mechanism at the origin of the fast damping as a Landau damping effect.

A fast, high-order solver for the Grad–Shafranov equation

International Nuclear Information System (INIS)

Pataki, Andras; Cerfon, Antoine J.; Freidberg, Jeffrey P.; Greengard, Leslie; O’Neil, Michael

2013-01-01

We present a new fast solver to calculate fixed-boundary plasma equilibria in toroidally axisymmetric geometries. By combining conformal mapping with Fourier and integral equation methods on the unit disk, we show that high-order accuracy can be achieved for the solution of the equilibrium equation and its first and second derivatives. Smooth arbitrary plasma cross-sections as well as arbitrary pressure and poloidal current profiles are used as initial data for the solver. Equilibria with large Shafranov shifts can be computed without difficulty. Spectral convergence is demonstrated by comparing the numerical solution with a known exact analytic solution. A fusion-relevant example of an equilibrium with a pressure pedestal is also presented

Fast current blinking in individual PbS and CdSe quantum dots.

Science.gov (United States)

Maturova, Klara; Nanayakkara, Sanjini U; Luther, Joseph M; van de Lagemaat, Jao

2013-06-12

Fast current intermittency of the tunneling current through single semiconductor quantum dots was observed through time-resolved intermittent contact conductive atomic force microscopy in the dark and under illumination at room temperature. The current through a single dot switches on and off at time scales ranging from microseconds to seconds with power-law distributions for both the on and off times. On states are attributed to the resonant tunneling of charges from the electrically conductive AFM tip to the quantum dot, followed by transfer to the substrate, whereas off states are attributed to a Coulomb blockade effect in the quantum dots that shifts the energy levels out of resonance conditions due to the presence of the trapped charge, while at the same bias. The observation of current intermittency due to Coulomb blockade effects has important implications for the understanding of carrier transport through arrays of quantum dots.

Mechanism of formation of subnanosecond current front in high-voltage pulse open discharge

Science.gov (United States)

Schweigert, I. V.; Alexandrov, A. L.; Zakrevsky, Dm. E.; Bokhan, P. A.

2014-11-01

The mechanism of subnanosecond current front rise observed previously in the experiment in high-voltage pulse open discharge in helium is studied in kinetic particle-in-cell simulations. The Boltzmann equations for electrons, ions, and fast atoms are solved self-consistently with the Poisson equations for the electrical potential. The partial contributions to the secondary electron emission from the ions, fast atoms, photons, and electrons, bombarding the electrode, are calculated. In simulations, as in the experiment, the discharge glows between two symmetrical cathodes and the anode grid in the midplane at P =6 Torr and the applied voltage of 20 kV. The electron avalanche development is considered for two experimental situations during the last stage of breakdown: (i) with constant voltage and (ii) with decreasing voltage. For case (i), the subnanosecond current front rise is set by photons from the collisional excitation transfer reactions. For the case (ii), the energetic electrons swamp the cathode during voltage drop and provide the secondary electron emission for the subnanosecond current rise, observed in the experiment.

Ultra-high efficiency, fast graphene micro-heater on silicon

DEFF Research Database (Denmark)

Yan, Siqi; Zhu, Xiaolong; Frandsen, Lars Hagedorn

2017-01-01

We demonstrate an ultra-high efficiency and fast graphene microheater on silicon photonic crystal waveguide. By taking advantage of slow-light effect, a tuning efficiency of 1.07 nm/mW and power consumption per free spectral range of 3.99 mW. A fast rise and decay times (10% to 90%) of only 750 ns...

Simple laser-driven, metal photocathodes as cold, high-current electron sources

International Nuclear Information System (INIS)

Saunders, J.D.; Ringler, T.J.; Builta, L.A.; Kauppila, T.J.; Moir, D.C.; Downey, S.W.

1987-01-01

Recent developments in excimer laser design have made near ultraviolet light intensities of several MWcm 2 possible in unfocused beams. These advances and recent experiments indicate that high-current, simple-metal photoemissive electron guns are now feasible. Producing more than 50 Acm 2 of illuminated cathode surface, the guns could operate at vacuums of 10 -6 torr with no complicated system components inside the vacuum enclosure. The electron beam produced by such photoemission guns would have very low emittance and high brightness. This beam would also closely follow the temporal characteristics of the laser pulse, making fast risetime, ultrashort electron beam pulses possible

High current ion sources

International Nuclear Information System (INIS)

Brown, I.G.

1989-06-01

The concept of high current ion source is both relative and evolutionary. Within the domain of one particular kind of ion source technology a current of microamperers might be 'high', while in another area a current of 10 Amperes could 'low'. Even within the domain of a single ion source type, what is considered high current performance today is routinely eclipsed by better performance and higher current output within a short period of time. Within their fields of application, there is a large number of kinds of ion sources that can justifiably be called high current. Thus, as a very limited example only, PIGs, Freemen sources, ECR sources, duoplasmatrons, field emission sources, and a great many more all have their high current variants. High current ion beams of gaseous and metallic species can be generated in a number of different ways. Ion sources of the kind developed at various laboratories around the world for the production of intense neutral beams for controlled fusion experiments are used to form large area proton deuteron beams of may tens of Amperes, and this technology can be used for other applications also. There has been significant progress in recent years in the use of microwave ion sources for high current ion beam generation, and this method is likely to find wide application in various different field application. Finally, high current beams of metal ions can be produced using metal vapor vacuum arc ion source technology. After a brief consideration of high current ion source design concepts, these three particular methods are reviewed in this paper

Fast electron transport in shaped solid targets

International Nuclear Information System (INIS)

Anle Lei; Cao, L.H.; He, X.T.; Zhang, W.Y.; Tanaka, K.A.; Kodama, R.; Mima, K.; Nakamura, T.; Normatsu, T.; Yu, W.

2010-01-01

Complete text of publication follows. The scheme of fast ignition fusion energy relies on the ultra-intense ultra-short (UIUS) laser energy transport into the compressed core plasma. One solution is to insert a hollow cone in the fuel shell to block the UIUS laser from the coronal plasma, thus allowing it to reach the core plasma. The cone not only can guide the UIUS laser to its tip, but can play important roles in the specific cone-in-shell target designed for FI. It was found in a PIC simulation that the cone can guide the fast electrons generated at the inner wall to propagate along the wall surface toward its tip, which would increase the energy density at the tip and might enhance the heating of the core plasma. Surface guiding of fast electrons with planar foil targets has been demonstrated experimentally. However, the guided fast electrons will mix the electrons generated ahead by the laser light with a planar target, and hence one cannot experimentally quantitatively validate the guide of the fast electrons. We investigate the cone guiding of fast electrons with an inverse cone target. We found a novel surface current of fast electrons propagating along the cone wall. The fast electrons generated at the planar outer tip of the inverse cone are guided and confined to propagate along the inverse cone wall to form a surface current by induced transient electric and magnetic fields associated with the current itself. Once departing from the source at the outer tip, this surface current of fast electrons is 'clean', neither experiencing the interacting laser light nor mixing fast electrons ahead, unlike those in cone or planar targets. This surface current in the inverse cone may explicitly give the capability of the guide of fast electron energy by the cone wall. The guiding and confinement of fast electrons is of important for fast ignition in inertial confinement fusion and several applications in high energy density science.

Design of a 10 MJ fast discharging homopolar machine

International Nuclear Information System (INIS)

Stillwagon, R.E.; Thullen, P.

1977-01-01

The design of a fast discharging homopolar machine is described. The machine capacity is 10 MJ with a 30 ms energy delivery time. The salient features of the machine are relatively high terminal voltage, fast discharge time, high power density and high efficiency. The machine integrates several new technologies including high surface speeds, large superconducting magnets and current collection at high density

Condition for a single bunch high frequency fast blow-up

International Nuclear Information System (INIS)

Wang, J.M.; Pellegrini, C.

1980-01-01

We study the longitudinal stability of a single particle bunch in a storage ring using Vlasov equation. We show that the Vlasov equation has solutions corresponding to a fast, microwave instability if a condition on the beam current, qualitatively similar to the stability condition for a coasting beam, is satisfied. This condition can be used to define a threshold current, and to discuss its dependence on the longitudinal coupling impedance

High Hydrogen Content Graphene Hydride Compounds & High Cross-­ Section Cladding Coatings for Fast Neutron Detection

Energy Technology Data Exchange (ETDEWEB)

Chandrashekhar, MVS [Univ. of South Carolina, Columbia, SC (United States)

2017-06-21

The objective is to develop and implement a superior low-cost, large area (potentially >32in), easily deployable, close proximity, harsh environment innovative neutron sensor needed for next generation fuel cycle monitoring. We will exploit recent breakthroughs at the PI’s lab on the electrochemistry of epitaxial graphene (EG) formed on commercial SiC wafers, a transformative nanomaterial system with superior radiation detection and durability properties to develop a new paradigm in detection for fast neutrons, a by-product of fission reactors. There are currently few effective detection/monitoring schemes, especially solid-state ones at present. This is essential for monitoring and control of future fuel cycles to make them more efficient and reliable. By exploiting these novel materials, as well as innovative hybrid SiC/EG/Cladding device architectures conceived by the team, will develop low-cost, high performance solutions to fast-neutron detection. Finally, we will also explore 3-terminal device implementations for neutron detectors with built-in electronic gain to further shrink these devices and improve their sensitivity.

High current, high bandwidth laser diode current driver

Science.gov (United States)

Copeland, David J.; Zimmerman, Robert K., Jr.

1991-01-01

A laser diode current driver has been developed for free space laser communications. The driver provides 300 mA peak modulation current and exhibits an optical risetime of less than 400 ps. The current and optical pulses are well behaved and show minimal ringing. The driver is well suited for QPPM modulation at data rates up to 440 Mbit/s. Much previous work has championed current steering circuits; in contrast, the present driver is a single-ended on/off switch. This results in twice the power efficiency as a current steering driver. The driver electrical efficiency for QPPM data is 34 percent. The high speed switch is realized with a Ku-band GaAsFET transistor, with a suitable pre-drive circuit, on a hybrid microcircuit adjacent to the laser diode.

Fast Food Consumption Behaviors in High-School Students based on the Theory of Planned Behavior (TPB)

OpenAIRE

Kamal Mirkarimi; Morteza Mansourian; Mohammad Javad Kabir; Rahman Berdi Ozouni- Davaji; Maryam Eri; Seyed Ghadir Hosseini; Mostafa Qorbani; Omid Safari; Babak Rastgari Mehr; Mehdi Noroozi; Abdurrahman Charkazi; Hossein Shahnazi

2016-01-01

Background: Studies report inappropriate snack and junk food consumption patterns in children and young adults in Iran. The current survey was aimed to explore fast food consumption behaviors in high-school students based on the Theory of Planned Behavior. Materials and Methods: A cross-sectional study was done among 500 high-school students. Samples were selected based on cluster sampling method at first and simple random at second. Data were collected using a researcher-made questionnaire. ...

Effects of buried high-Z layers on fast electron propagation

International Nuclear Information System (INIS)

Yang, Xiaohu; Zhuo, Hongbin; Ma, Yanyun; Shao, Fuqiu; Xu, Han; Yin Yan; Borghesi, M.

2014-01-01

The transport through high density plasmas of relativistic electron beams generated by ultra-intense laser-plasma interaction has potential applications in laser-driven ion acceleration and in the fast igniter scheme for inertial confinement fusion. By extending a prior model [A.R. Bell, J.R. Davies, S.M. Guerin, Phys. Rev. E 58, 2471 (1998)], the magnetic field generated during the transport of a fast electron beam driven by an ultra-intense laser in a solid target is derived analytically and applied to estimate the effect of such field on fast electron propagation through a buried high-Z layer in a lower-Z target. It is found that the effect gets weaker with the increase of the depth of the buried layer, the divergence of the fast electrons, and the laser intensity, indicating that magnetic field effects on the fast electron divergence as measured from K a X-ray emission may need to be considered for moderate laser intensities. On the basis of the calculations, some considerations are made on how one can mitigate the effect of the magnetic field generated at the interface. (authors)

Fast Coordinated Control of DFIG Wind Turbine Generators for Low and High Voltage Ride-Through

Directory of Open Access Journals (Sweden)

Yun Wang

2014-06-01

Full Text Available This paper presents a fast coordinated control scheme of the rotor side converter (RSC, the Direct Current (DC chopper and the grid side converter (GSC of doubly fed induction generator (DFIG wind turbine generators (WTGs to improve the low voltage ride through (LVRT and high voltage ride through (HVRT capability of the DFIG WTGs. The characteristics of DFIG WTGs under voltage sags and swells were studied focusing on the DFIG WTG stator flux and rotor voltages during the transient periods of grid voltage changes. The protection schemes of the rotor crowbar circuit and the DC chopper circuit were proposed considering the characteristics of the DFIG WTGs during voltage changes. The fast coordinated control of RSC and GSC were developed based on the characteristic analysis in order to realize efficient LVRT and HVRT of the DFIG WTGs. The proposed fast coordinated control schemes were verified by time domain simulations using Matlab-Simulink.

Tomography of the fast electron Bremsstrahlung emission during lower hybrid current drive on Tore Supra

Energy Technology Data Exchange (ETDEWEB)

Peysson, Y.; Imbeaux, F. [Association Euratom-CEA, CEA/Cadarache, Dept. de Recherches sur la Fusion Controlee (DRFC), 13 - Saint-Paul-lez-Durance (France)

1999-04-01

A new tomography dedicated to detailed studies of the fast electron Bremsstrahlung emission in the hard X-ray (HXR) energy range between 20 and 200 keV during lower hybrid (LH) current drive experiments on the TORE SUPRA tokamak [Equipe TORE SUPRA, in Proceedings of the 15. Conference on Plasma Physics and Controlled Nuclear Fusion Research, Seville (International Atomic Energy Agency, Vienna, 1995), 1, AIEA-CN-60 / A1-5, p. 105] is presented. Radiation detection is performed by cadmium telluride(CdTe) semiconductors, which have most of the desirable features for a powerful diagnosing of magnetically confined hot plasmas - compact size, high X-ray stopping efficiency, fast timing characteristics, good energy resolution, no sensitivity to magnetic field, reasonable susceptibility to performance degradation from neutron/{gamma}-induced damages. This instrument is made of two independent cameras viewing a poloidal cross-section of the plasma, with respectively 21 and 38 detectors. A coarse spectrometry - 8 energy channels - is carried out for each chord, with an energy resolution of 20 keV. The spatial resolution in the core of the plasma is 4-5 cm, while the time sampling may be lowered down to of 2-4 ms. Powerful inversion techniques based on maximum entropy or regularization algorithms take fully advantage of the large number of line-integrated measurements for very robust estimates of the local HXR profiles as a function of time and photon energy. A detailed account of main characteristics and performances of the diagnostic is reported as well as preliminary results on LH current drive experiments. (authors)

Tomography of the fast electron Bremsstrahlung emission during lower hybrid current drive on Tore Supra

International Nuclear Information System (INIS)

Peysson, Y.; Imbeaux, F.

1999-04-01

A new tomography dedicated to detailed studies of the fast electron Bremsstrahlung emission in the hard X-ray (HXR) energy range between 20 and 200 keV during lower hybrid (LH) current drive experiments on the TORE SUPRA tokamak [Equipe TORE SUPRA, in Proceedings of the 15. Conference on Plasma Physics and Controlled Nuclear Fusion Research, Seville (International Atomic Energy Agency, Vienna, 1995), 1, AIEA-CN-60 / A1-5, p. 105] is presented. Radiation detection is performed by cadmium telluride (CdTe) semiconductors, which have most of the desirable features for a powerful diagnosing of magnetically confined hot plasmas - compact size, high X-ray stopping efficiency, fast timing characteristics, good energy resolution, no sensitivity to magnetic field, reasonable susceptibility to performance degradation from neutron/γ-induced damages. This instrument is made of two independent cameras viewing a poloidal cross-section of the plasma, with respectively 21 and 38 detectors. A coarse spectrometry - 8 energy channels - is carried out for each chord, with an energy resolution of 20 keV. The spatial resolution in the core of the plasma is 4-5 cm, while the time sampling may be lowered down to of 2-4 ms. Powerful inversion techniques based on maximum entropy or regularization algorithms take fully advantage of the large number of line-integrated measurements for very robust estimates of the local HXR profiles as a function of time and photon energy. A detailed account of main characteristics and performances of the diagnostic is reported as well as preliminary results on LH current drive experiments. (authors)

Fast response double series resonant high-voltage DC-DC converter

International Nuclear Information System (INIS)

Lee, S S; Iqbal, S; Kamarol, M

2012-01-01

In this paper, a novel double series resonant high-voltage dc-dc converter with dual-mode pulse frequency modulation (PFM) control scheme is proposed. The proposed topology consists of two series resonant tanks and hence two resonant currents flow in each switching period. Moreover, it consists of two high-voltage transformer with the leakage inductances are absorbed as resonant inductor in the series resonant tanks. The secondary output of both transformers are rectified and mixed before supplying to load. In the resonant mode operation, the series resonant tanks are energized alternately by controlling two Insulated Gate Bipolar Transistor (IGBT) switches with pulse frequency modulation (PFM). This topology operates in discontinuous conduction mode (DCM) with all IGBT switches operating in zero current switching (ZCS) condition and hence no switching loss occurs. To achieve fast rise in output voltage, a dual-mode PFM control during start-up of the converter is proposed. In this operation, the inverter is started at a high switching frequency and as the output voltage reaches 90% of the target value, the switching frequency is reduced to a value which corresponds to the target output voltage. This can effectively reduce the rise time of the output voltage and prevent overshoot. Experimental results collected from a 100-W laboratory prototype are presented to verify the effectiveness of the proposed system.

Multishot echo-planar MREIT for fast imaging of conductivity, current density, and electric field distributions.

Science.gov (United States)

Chauhan, Munish; Vidya Shankar, Rohini; Ashok Kumar, Neeta; Kodibagkar, Vikram D; Sadleir, Rosalind

2018-01-01

Magnetic resonance electrical impedance tomography (MREIT) sequences typically use conventional spin or gradient echo-based acquisition methods for reconstruction of conductivity and current density maps. Use of MREIT in functional and electroporation studies requires higher temporal resolution and faster sequences. Here, single and multishot echo planar imaging (EPI) based MREIT sequences were evaluated to see whether high-quality MREIT phase data could be obtained for rapid reconstruction of current density, conductivity, and electric fields. A gel phantom with an insulating inclusion was used as a test object. Ghost artifact, geometric distortion, and MREIT correction algorithms were applied to the data. The EPI-MREIT-derived phase-projected current density and conductivity images were compared with simulations and spin-echo images as a function of EPI shot number. Good agreement among measures in simulated, spin echo, and EPI data was achieved. Current density errors were stable and below 9% as the shot number decreased from 64 to 2, but increased for single-shot images. Conductivity reconstruction relative contrast ratios were stable as the shot number decreased. The derived electric fields also agreed with the simulated data. The EPI methods can be combined successfully with MREIT reconstruction algorithms to achieve fast imaging of current density, conductivity, and electric field. Magn Reson Med 79:71-82, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Exploration of high harmonic fast wave heating on the National Spherical Torus Experiment

International Nuclear Information System (INIS)

Wilson, J.R.; Bell, R.E.; Bernabei, S.; Bitter, M.; Gates, D.; Hosea, J.; Le Blanc, B.; Medley, S.; Menard, J.; Mueller, D.; Ono, M.; Phillips, C.K.; Rosenberg, A.; Bonoli, P.; Mau, T.K.; Pinsker, R.I.; Raman, R.; Ryan, P.; Swain, D.; Wilgen, J.

2003-01-01

High harmonic fast wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [M. Ono, S. M. Kaye, S. Neumeyer et al., in Proceedings of the 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999 (IEEE, Piscataway, NJ, 1999), p. 53] is such a device. An rf heating system has been installed on the NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the ST concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge

A fast charge-integrating sample-and-hold circuit for fast decision-making with calorimeter arrays

International Nuclear Information System (INIS)

Schuler, G.

1982-01-01

This paper describes a fast charge-integrating sample-and-hold circuit, particularly suited to the fast trigger electronics used with large arrays of photomultipliers in total-energy measurements of high-energy particles interactions. During a gate logic pulse, the circuit charges a capacitor with the current fed into the signal input. The output voltage is equal to the voltage developed across the capacitor, which is held until a fast clear discharges the capacitor. The main characteristics of the fast-charge-integrating sample-and-hold circuit are: i) a conversion factor of 1 V/220 pC; ii) a droop rate of 4 mV/μs for a 50 Ω load; and iii) a 1 μs fast-clear time. (orig.)

Photoperiod Modulates Fast Delayed Rectifier Potassium Currents in the Mammalian Circadian Clock.

Science.gov (United States)

Farajnia, Sahar; Meijer, Johanna H; Michel, Stephan

2016-10-01

One feature of the mammalian circadian clock, situated in the suprachiasmatic nucleus (SCN), is its ability to measure day length and thereby contribute to the seasonal adaptation of physiology and behavior. The timing signal from the SCN, namely the 24 hr pattern of electrical activity, is adjusted according to the photoperiod being broader in long days and narrower in short days. Vasoactive intestinal peptide and gamma-aminobutyric acid play a crucial role in intercellular communication within the SCN and contribute to the seasonal changes in phase distribution. However, little is known about the underlying ionic mechanisms of synchronization. The present study was aimed to identify cellular mechanisms involved in seasonal encoding by the SCN. Mice were adapted to long-day (light-dark 16:8) and short-day (light-dark 8:16) photoperiods and membrane properties as well as K + currents activity of SCN neurons were measured using patch-clamp recordings in acute slices. Remarkably, we found evidence for a photoperiodic effect on the fast delayed rectifier K + current, that is, the circadian modulation of this ion channel's activation reversed in long days resulting in 50% higher peak values during the night compared with the unaltered day values. Consistent with fast delayed rectifier enhancement, duration of action potentials during the night was shortened and afterhyperpolarization potentials increased in amplitude and duration. The slow delayed rectifier, transient K + currents, and membrane excitability were not affected by photoperiod. We conclude that photoperiod can change intrinsic ion channel properties of the SCN neurons, which may influence cellular communication and contribute to photoperiodic phase adjustment. © The Author(s) 2016.

Photoperiod Modulates Fast Delayed Rectifier Potassium Currents in the Mammalian Circadian Clock

Directory of Open Access Journals (Sweden)

Sahar Farajnia

2016-09-01

Full Text Available One feature of the mammalian circadian clock, situated in the suprachiasmatic nucleus (SCN, is its ability to measure day length and thereby contribute to the seasonal adaptation of physiology and behavior. The timing signal from the SCN, namely the 24 hr pattern of electrical activity, is adjusted according to the photoperiod being broader in long days and narrower in short days. Vasoactive intestinal peptide and gamma-aminobutyric acid play a crucial role in intercellular communication within the SCN and contribute to the seasonal changes in phase distribution. However, little is known about the underlying ionic mechanisms of synchronization. The present study was aimed to identify cellular mechanisms involved in seasonal encoding by the SCN. Mice were adapted to long-day (light–dark 16:8 and short-day (light–dark 8:16 photoperiods and membrane properties as well as K+ currents activity of SCN neurons were measured using patch-clamp recordings in acute slices. Remarkably, we found evidence for a photoperiodic effect on the fast delayed rectifier K+ current, that is, the circadian modulation of this ion channel’s activation reversed in long days resulting in 50% higher peak values during the night compared with the unaltered day values. Consistent with fast delayed rectifier enhancement, duration of action potentials during the night was shortened and afterhyperpolarization potentials increased in amplitude and duration. The slow delayed rectifier, transient K+ currents, and membrane excitability were not affected by photoperiod. We conclude that photoperiod can change intrinsic ion channel properties of the SCN neurons, which may influence cellular communication and contribute to photoperiodic phase adjustment.

Non-fasting factor VII coagulant activity (FVII:C) increased by high-fat diet

DEFF Research Database (Denmark)

Bladbjerg, Else-Marie; Marckmann, P; Sandström, B

1994-01-01

:Bt/FVII:Am (a measure of FVII activation) increased from fasting levels on both diets, but most markedly on the high-fat diet. In contrast, FVII:Am (a measure of FVII protein) tended to decrease from fasting levels on both diets. FVII:C rose from fasting levels on the high-fat diet, but not on the low-fat diet....... The findings suggest that high-fat diets increase non-fasting FVII:C, and consequently may be associated with increased risk of thrombosis. Udgivelsesdato: 1994-Jun......Preliminary observations have suggested that non-fasting factor VII coagulant activity (FVII:C) may be related to the dietary fat content. To confirm this, we performed a randomised cross-over study. Seventeen young volunteers were served 2 controlled isoenergetic diets differing in fat content (20...

High Intensity Exercise: Can It Protect You from A Fast Food Diet?

Science.gov (United States)

Duval, Christian; Rouillier, Marc-Antoine; Rabasa-Lhoret, Rémi; Karelis, Antony D

2017-08-26

The purpose of this study was to assess the ability of high intensity exercise to counteract the deleterious effects of a fast food diet on the cardiometabolic profile of young healthy men. Fifteen men were subjected to an exclusive fast food diet from a popular fast food restaurant chain (three extra value meals/day + optional snack) for 14 consecutive days. Simultaneously, participants were asked to perform each day high intensity interval training (HIIT) (15 × 60 sec sprint intervals (~90% of maximal heart rate)) on a treadmill. Fast food diet and energy expenditure profiles of the participants during the intervention were assessed as well as body composition (DXA), cardiometabolic profile (lipid, hepatic enzymes, glycated hemoglobin, glucose, insulin, hsC-reactive protein (hsCRP) and blood pressure) and estimated maximal oxygen consumption (VO2 max) pre- and post-experiment. We found significant improvements for fat mass, lean body mass, estimated VO₂ max, fasting glucose, serum lipoprotein(a) and hsCRP after the intervention ( p fast food diet.

The effect of plasma parameter on the bootstrap current of fast ions in neutral beam injection

International Nuclear Information System (INIS)

Huang Qianhong; Gong Xueyu; Cao Jinjia; Yang Lei

2014-01-01

The effect of plasma parameters on the distribution of net current density of fast ions produced by neutral beam injection is investigated in a large-aspect-ratio Tokamak with circular cross-section under specific parameters. Numerical results show that the value of net current density increases with the temperature of plasma increasing and decreases with the density of plasma increasing. The value of net current density is weakly affected by the effective charge number, but the peak of net current density moves towards edge plasma with effective charge number increasing. (authors)

RF power diagnostics and control on the DIII-D, 4 MW 30--120 MHz fast wave current drive system (FWCD)

International Nuclear Information System (INIS)

Ferguson, S.W.; Allen, J.C.; Callis, R.W.; Cary, W.P.; Harris, T.E.

1995-10-01

The Fast Wave Current Drive System uses three 2 MW transmitters to drive three antennas inside the DIII-D vacuum vessel. This paper describes the diagnostics for this system. The diagnostics associated with the General Atomics Fast Wave Current Drive System allow the system tuning to be analyzed and modified on a between shot basis. The transmitters can be exactly tuned to match the plasma with only one tuning shot into the plasma. This facilitates maximum rf power utilization

Current status and directions for fast reactor reprocessing

International Nuclear Information System (INIS)

Burch, W.D.

1983-01-01

The development of fast breeder reactors (FBRs) for commercial electric power production has been under way in several countries for more than 20 years. In the United States (US), as elsewhere, early work was focused on small reactors to prove the feasibility of concepts and later was followed by larger reactors to test engineering features and to develop fuel technology. Because of the perceived crisis in electrical generation expected late in this century, major efforts (including fuel cycle activities) were developed in the early 1970s to ensure the capability of developing and using this new form of nuclear power. However, because of the effects of the oil price rise and subsequent emphasis on conservation, and a slowdown of industrial growth, there has been a decline in such activities, particularly in the US, which was at one time (1970s) the world leader in reactor development. This paper provides a brief history of breeder reprocessing and describes the current status, with emphasis on US programs and glimpses into the future

Cryogenic high current discharges

International Nuclear Information System (INIS)

Meierovich, B.E.

1994-01-01

Z-pinches formed from frozen deuterium fibers by a rapidly rising current have enhanced stability and high neutron yield. The efforts to understand the enhanced stability and neutron yield on the basis of classical picture of Bennett equilibrium of the current channel has not given satisfactory results. The traditional approach does not take into account the essential difference between the frozen deuterium fiber Z-pinches and the usual Z-pinches such as exploding wires or classical gas-puffed Z-pinches. The very low temperature of the fiber atoms (10 K), together with the rapidly rising current, result in the coexistence of a high current channel with unionized fiber atoms for a substantial period of time. This phenomena lasts during the risetime. This approach takes into account the difference of the breakdown in a dielectric deuterium fiber and the breakdown in a metallic wire. This difference is essential to the understanding of specific features of cryogenic high current discharges. Z-pinches in frozen deuterium fibers should be considered as a qualitatively new phenomenon on the boundary of cryogenic and high current physics. It is a start of a new branch in plasma physics: the physics of cryogenic high current discharges

Seizure-induced alterations in fast-spiking basket cell GABA currents modulate frequency and coherence of gamma oscillation in network simulations

International Nuclear Information System (INIS)

Proddutur, Archana; Yu, Jiandong; Elgammal, Fatima S.; Santhakumar, Vijayalakshmi

2013-01-01

Gamma frequency oscillations have been proposed to contribute to memory formation and retrieval. Fast-spiking basket cells (FS-BCs) are known to underlie development of gamma oscillations. Fast, high amplitude GABA synapses and gap junctions have been suggested to contribute to gamma oscillations in FS-BC networks. Recently, we identified that, apart from GABAergic synapses, FS-BCs in the hippocampal dentate gyrus have GABAergic currents mediated by extrasynaptic receptors. Our experimental studies demonstrated two specific changes in FS-BC GABA currents following experimental seizures [Yu et al., J. Neurophysiol. 109, 1746 (2013)]: increase in the magnitude of extrasynaptic (tonic) GABA currents and a depolarizing shift in GABA reversal potential (E GABA ). Here, we use homogeneous networks of a biophysically based model of FS-BCs to examine how the presence of extrasynaptic GABA conductance (g GABA-extra ) and experimentally identified, seizure-induced changes in g GABA-extra and E GABA influence network activity. Networks of FS-BCs interconnected by fast GABAergic synapses developed synchronous firing in the dentate gamma frequency range (40–100 Hz). Systematic investigation revealed that the biologically realistic range of 30 to 40 connections between FS-BCs resulted in greater coherence in the gamma frequency range when networks were activated by Poisson-distributed dendritic synaptic inputs rather than by homogeneous somatic current injections, which were balanced for FS-BC firing frequency in unconnected networks. Distance-dependent conduction delay enhanced coherence in networks with 30–40 FS-BC interconnections while inclusion of gap junctional conductance had a modest effect on coherence. In networks activated by somatic current injections resulting in heterogeneous FS-BC firing, increasing g GABA-extra reduced the frequency and coherence of FS-BC firing when E GABA was shunting (−74 mV), but failed to alter average FS-BC frequency when E GABA

Observation of a very high electron current extraction mode in a hollow cathode discharge

International Nuclear Information System (INIS)

Hershcovitch, A.

1993-01-01

Earlier results by Hershcovitch, Kovarik, and Prelec in J. Appl. Phys. 67, 671 (1990) proved that, in a low-pressure operating mode, hollow cathode discharges can have a two-component electron population, one of which is that of ''fast'' electrons having an energy corresponding to the cathode potential and a thermal spread of about 0.13 eV, which could form a basis for an excellent electron gun. Investigations of extracted electron currents in this low pressure mode indicate the existence of a narrow pressure range characterized by very high electron current extraction

Fast switching thyristor applied in nanosecond-pulse high-voltage generator with closed transformer core.

Science.gov (United States)

Li, Lee; Bao, Chaobing; Feng, Xibo; Liu, Yunlong; Fochan, Lin

2013-02-01

For a compact and reliable nanosecond-pulse high-voltage generator (NPHVG), the specification parameter selection and potential usage of fast controllable state-solid switches have an important bearing on the optimal design. The NPHVG with closed transformer core and fast switching thyristor (FST) was studied in this paper. According to the analysis of T-type circuit, the expressions for the voltages and currents of the primary and secondary windings on the transformer core of NPHVG were deduced, and the theoretical maximum analysis was performed. For NPHVG, the rise-rate of turn-on current (di/dt) across a FST may exceed its transient rating. Both mean and maximum values of di/dt were determined by the leakage inductances of the transformer, and the difference is 1.57 times. The optimum winding ratio is helpful to getting higher voltage output with lower specification FST, especially when the primary and secondary capacitances have been established. The oscillation period analysis can be effectively used to estimate the equivalent leakage inductance. When the core saturation effect was considered, the maximum di/dt estimated from the oscillating period of the primary current is more accurate than one from the oscillating period of the secondary voltage. Although increasing the leakage inductance of NPHVG can decrease di/dt across FST, it may reduce the output peak voltage of the NPHVG.

Current-drive on the Versator-II tokamak with a slotted-waveguide fast-wave coupler

International Nuclear Information System (INIS)

Colborn, J.A.

1987-11-01

A slotted-waveguide fast-wave coupler has been constructed, without dielectric, and used to drive current on the Versator-II tokamak. Up to 35 kW of net microwave power at 2.45 GHz has been radiated into plasmas with 2 x 10 12 cm -3 ≤ mean of n/sub e/ ≤ 1.2 x 10 13 cm -3 and B/sub tor/ ≅ 1.0 T. The launched spectrum had a peak near N/sub parallel/ = -2.0 and a larger peak near N/sub parallel/ = 0.7. Radiating efficiency of the antenna was roughly independent of antenna position except when the antenna was at least 0.2 cm outside the limiter, in which case the radiating efficiency slightly improved as the antenna was moved farther outside. When the coupler was inside the limiter, radiating efficiency improved moderately with increased mean of n/sub e/. Current-drive efficiency was comparable to that of the slow wave and was not affected when the antenna spectrum was reversed; however, no current was driven for mean of n/sub e/ ≤ 2 x 10 12 cm -3 . These results indicate the fast wave was launched, but a substantial part of the power may have been mode-converted to the slow wave, possibly via a downshift in N/sub parallel/, and these slow waves may have been responsible for most of the driven current. Relevant theory for waves in plasma, current-drive efficiency, and coupling of the slotted-waveguide is discussed, the antenna design method is explained, and future work, including the construction of a much-improved probe-fed antenna, is described. 42 refs., 45 figs

Ultra-fast magnetization reversal in magnetic nano-pillars by spin-polarized current

Energy Technology Data Exchange (ETDEWEB)

Devolder, T. [Institut d' Electronique Fondamentale, UMR 8622 CNRS, Universite Paris Sud, Ba-circumflex timent 220, 91405 Orsay (France)]. E-mail: thibaut.devolder@ief.u-psud.fr; Tulapurkar, A. [NanoElectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568 (Japan); CREST, Japan Science and Technology Corporation, 4-1-8 Honcho, Kawaguchi 332-0012 (Japan); Yagami, K. [SSNC, Semiconductor Technology Development Group, SONY Corporation, Atsugi, Kanagawa 243-0014 (Japan); Crozat, P. [Institut d' Electronique Fondamentale, UMR 8622 CNRS, Universite Paris Sud, Ba-circumflex timent 220, 91405 Orsay (France); Chappert, C. [Institut d' Electronique Fondamentale, UMR 8622 CNRS, Universite Paris Sud, Ba-circumflex timent 220, 91405 Orsay (France); Fukushima, A. [NanoElectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568 (Japan); CREST, Japan Science and Technology Corporation, 4-1-8 Honcho, Kawaguchi 332-0012 (Japan); Suzuki, Y. [NanoElectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568 (Japan); CREST, Japan Science and Technology Corporation, 4-1-8 Honcho, Kawaguchi 332-0012 (Japan)

2005-02-01

We study the speed limitations of the magnetization switching resulting from spin transfer in pillar-shaped CoFe/Cu/CoFe spin valves. The quasi-static critical currents are Ic-=-2mA for the antiparallel (AP) to parallel (P) configuration and Ic+=+4.6mA for the P to AP transition. Current pulses of duration down to 100ps and amplitude of 4I{sub c} trigger switching at 300K. The switching is probabilistic for lower current pulses. The P to AP transition speed is not much temperature dependant from 50 to 300K. In contrast, the AP to P transition is thermally inhibited and is much faster at 150K than at 300K. This thermal inhibition highlights the importance of the macrospin coherency and of the thermally excited spin waves with finite wave vector parallel to the magnetization. Our results validate spin-transfer switching for fast memory applications.

Ultra-fast magnetization reversal in magnetic nano-pillars by spin-polarized current

International Nuclear Information System (INIS)

Devolder, T.; Tulapurkar, A.; Yagami, K.; Crozat, P.; Chappert, C.; Fukushima, A.; Suzuki, Y.

2005-01-01

We study the speed limitations of the magnetization switching resulting from spin transfer in pillar-shaped CoFe/Cu/CoFe spin valves. The quasi-static critical currents are Ic-=-2mA for the antiparallel (AP) to parallel (P) configuration and Ic+=+4.6mA for the P to AP transition. Current pulses of duration down to 100ps and amplitude of 4I c trigger switching at 300K. The switching is probabilistic for lower current pulses. The P to AP transition speed is not much temperature dependant from 50 to 300K. In contrast, the AP to P transition is thermally inhibited and is much faster at 150K than at 300K. This thermal inhibition highlights the importance of the macrospin coherency and of the thermally excited spin waves with finite wave vector parallel to the magnetization. Our results validate spin-transfer switching for fast memory applications

High-voltage high-current triggering vacuum switch

International Nuclear Information System (INIS)

Alferov, D.F.; Bunin, R.A.; Evsin, D.V.; Sidorov, V.A.

2012-01-01

Experimental investigations of switching and breaking capacities of the new high current triggered vacuum switch (TVS) are carried out at various parameters of discharge current. It has been shown that the high current triggered vacuum switch TVS can switch repeatedly a current from units up to ten kiloampers with duration up to ten millisecond [ru

Construction of a High Temporal-spectral Resolution Spectrometer for Detection of Fast Transients from Observations of the Sun at 1.4 GHz.

Science.gov (United States)

Casillas-Perez, G. A.; Jeyakumar, S.; Perez-Enriquez, R.

2014-12-01

Transients explosive events with time durations from nanoseconds to several hours, are observed in the Sun at high energy bands such as gamma ray and xray. In the radio band, several types of radio bursts are commonly detected from the ground. A few observations of the Sun in the past have also detected a new class of fast transients which are known to have short-live electromagnetic emissions with durations less than 100 ms. The mechanisms that produce such fast transiets remain unclear. Observations of such fast transients over a wide bandwidth is necessary to uderstand the underlying physical process that produce such fast transients. Due to their very large flux densities, fast radio transients can be observed at high time resolution using small antennas in combination with digital signal processing techniques. In this work we report the progress of an spectrometer that is currently in construction at the Observatorio de la Luz of the Universidad de Guanajuato. The instrument which will have the purpose of detecting solar fast radio transients, involves the use of digital devices such as FPGA and ADC cards, in addition with a receiver with high temporal-spectral resolution centered at 1.4 GHz and a pair of 2.3 m satellite dish.

Pricing strategy for products in the healthy fast food sector in Stockholm

OpenAIRE

Hermann, Tim

2015-01-01

The demand of fast food is increasing in current food market worldwide. But fast food, as one of the unhealthy food types, cannot deny its impact as one of the causes of leading death in populations of most high income countries. Healthy fast food is called by governments, health organizations and societies, and desired by customers especially in Sweden because it is affordable, easy accessible, and most immortally, healthy. Companies are emerging based on the current fast food demand to prov...

Fast High-Quality Noise

DEFF Research Database (Denmark)

Frisvad, Jeppe Revall; Wyvill, Geoff

2007-01-01

At the moment the noise functions available in a graphics programmer's toolbox are either slow to compute or they involve grid-line artifacts making them of lower quality. In this paper we present a real-time noise computation with no grid-line artifacts or other regularity problems. In other words......, we put a new tool in the box that computes fast high-quality noise. In addition to being free of artifacts, the noise we present does not rely on tabulated data (everything is computed on the fly) and it is easy to adjust quality vs. quantity for the noise. The noise is based on point rendering (like...... spot noise), but it extends to more than two dimensions. The fact that it is based on point rendering makes art direction of the noise much easier....

Measurement technology of RF interference current in high current system

Science.gov (United States)

Zhao, Zhihua; Li, Jianxuan; Zhang, Xiangming; Zhang, Lei

2018-06-01

Current probe is a detection method commonly used in electromagnetic compatibility. With the development of power electronics technology, the power level of power conversion devices is constantly increasing, and the power current of the electric energy conversion device in the electromagnetic launch system can reach 10kA. Current probe conventionally used in EMC (electromagnetic compatibility) detection cannot meet the test requirements on high current system due to the magnetic saturation problem. The conventional high current sensor is also not suitable for the RF (Radio Frequency) interference current measurement in high current power device due to the high noise level in the output of active amplifier. In this paper, a passive flexible current probe based on Rogowski coil and matching resistance is proposed that can withstand high current and has low noise level, to solve the measurement problems of interference current in high current power converter. And both differential mode and common mode current detection can be easily carried out with the proposed probe because of the probe's flexible structure.

A Decentralized Current-Sharing Controller Endows Fast Transient Response to Parallel DC-DC Converters

DEFF Research Database (Denmark)

Wang, Haojie; Han, Minxiao; Han, Renke

2018-01-01

This paper proposes a decentralized current-sharing control strategy to endow fast transient response to paralleled DC-DC converters systems, such as DC microgrids or distributed power systems. The proposed controller consist of two main control loops: an external voltage droop control for current......-sharing proposes and an internal current loop. The external droop control loop is designed as a voltage loop with embedded virtual impedance, which avoids the use of a slow voltage loop and a separate extra virtual impedance loop that may limit the system bandwidth. The internal current loop, thanks...... and the proposed embedded-virtual-impedance based I-V droop. In order to compare the dynamic response performances between two droop controllers, their state-space models have been developed and analyzed in this paper. The results show that the dynamic response of the I-V droop control is faster than...

Experimental study of collective effects in BEP storage ring with high stored current

International Nuclear Information System (INIS)

Danilov, V.; Koop, I.; Lysenko, A.; Militsyn, B.; Nesterenko, I.; Perevedentsev, E.; Pozdeev, E.; Ptitsin, V.; Shatunov, Yu.; Vasserman, I.

1993-01-01

The results of extensive investigation of beam dynamics with high current in BEP booster are presented. Strong bunch lengthening due to the potential well distortion by the inductive impedance was observed on the background of the multiple intrabeam scattering and of the ion accumulation (in the e - beam). The octupole and sextupole corrections enabled control of collective damping of the head-tail modes. Fast damping is also observed at zero chromaticity, this is attributed to the injection kickers acting as transmission lines. The proper tuning of the nonlinearity corrections cures the transverse instabilities and enables capability to store up to 0.8A current in a single bunch

Production of a high-current microsecond electron beam with a large cross section

International Nuclear Information System (INIS)

Abdullin, E.N.; Belomytsev, S.Ya.; Bugaev, S.P.; Gorbachev, S.I.; Zaslavskii, V.M.; Zorin, V.P.; Koval'chuk, B.M.; Loginov, S.V.; Matyukov, Yu.N.; Rasputin, R.M.; Tolkachev, V.S.; Shchanin, P.M.

1991-01-01

Obtaining high-current wide-aperture electron beams is an important problem in the development of laser technology for controlled nuclear fusion and for solving ecological and technological problems. The main scheme for producing such beams involves the use of generators with intermediate energy storage devices and burst-emission vacuum diodes. Beam pinching is prevented by using an external magnetic field or sectioning the diode into magnetically insulated diodes with currents lower than the limiting current. The length of the electron-current pulse varies from tens to hundreds of nano-seconds and is limited by the parameters of the intermediate storage device. Here the authors study the formation of a high-current electron beam with a square cross section and a current of the order of the limiting current of the diode in the absence of an external magnetic field as well as a 'fast' storage device in the power supply circuit. These conditions as a whole correspond to a simpler electron-source circuit, but the beam forming becomes more complicated. The reason for this is that there is no external magnetic field and that the role of plasma processes in the diode is enhanced by the greater length of the electron-current pulses

Preoperative fasting times: Prescribed and actual fasting times at ...

African Journals Online (AJOL)

The current international guidelines for preoperative fasting for elective surgery are 6 ... to determine whether this policy was being followed and patients were being starved ..... recommended fasting time, so that autonomous patients take care.

Low power fast settling multi-standard current reusing CMOS fractional-N frequency synthesizer

Institute of Scientific and Technical Information of China (English)

Lou Wenfeng; Feng Peng; Wang Haiyong; Wu Nanjian

2012-01-01

A low power fast settling multi-standard CMOS fractional-N frequency synthesizer is proposed.The current reusing and frequency presetting techniques are adopted to realize the low power fast settling multi-standard fractional-N frequency synthesizer.An auxiliary non-volatile memory (NVM) is embedded to avoid the repetitive calibration process and to save power in practical application.This PLL is implemented in a 0.18μm technology.The frequency range is 0.3 to 2.54 GHz and the settling time is less than 5μs over the entire frequency range.The LC-VCO with the stacked divide-by-2 has a good figure of merit of-193.5 dBc/Hz.The measured phase noise of frequency synthesizer is about -115 dBc/Hz at 1 MHz offset when the carrier frequency is 2.4 GHz and the reference spurs are less than -52 dBc.The whole frequency synthesizer consumes only 4.35 mA @ 1.8 V.

IceCube constraints on fast-spinning pulsars as high-energy neutrino sources

Energy Technology Data Exchange (ETDEWEB)

Fang, Ke [Department of Astronomy, University of Maryland, College Park, MD, 20742 (United States); Kotera, Kumiko [Institut d' Astrophysique de Paris, UMR 7095 – CNRS, Université Pierre $ and $ Marie Curie, 98 bis boulevard Arago, 75014, Paris (France); Murase, Kohta [Department of Physics, Department of Astronomy and Astrophysics, Center for Particle and Gravitational Astrophysics, The Pennsylvania State University, PA 16802 (United States); Olinto, Angela V., E-mail: kefang@umd.edu, E-mail: kotera@iap.fr, E-mail: murase@psu.edu, E-mail: olinto@kicp.uchicago.edu [Department of Astronomy and Astrophysics, Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637 (United States)

2016-04-01

Relativistic winds of fast-spinning pulsars have been proposed as a potential site for cosmic-ray acceleration from very high energies (VHE) to ultrahigh energies (UHE). We re-examine conditions for high-energy neutrino production, considering the interaction of accelerated particles with baryons of the expanding supernova ejecta and the radiation fields in the wind nebula. We make use of the current IceCube sensitivity in diffusive high-energy neutrino background, in order to constrain the parameter space of the most extreme neutron stars as sources of VHE and UHE cosmic rays. We demonstrate that the current non-observation of 10{sup 18} eV neutrinos put stringent constraints on the pulsar scenario. For a given model, birthrates, ejecta mass and acceleration efficiency of the magnetar sources can be constrained. When we assume a proton cosmic ray composition and spherical supernovae ejecta, we find that the IceCube limits almost exclude their significant contribution to the observed UHE cosmic-ray flux. Furthermore, we consider scenarios where a fraction of cosmic rays can escape from jet-like structures piercing the ejecta, without significant interactions. Such scenarios would enable the production of UHE cosmic rays and help remove the tension between their EeV neutrino production and the observational data.

Fast Kicker for High Current Beam Manipulation in Large Aperture

CERN Document Server

Gambaryan, V

2017-01-01

The pulsed deflecting magnet (kicker) project was worked out in Budker Institute of Nuclear Physics. The kicker design parameters are: impulsive force, 1 mT*m; pulse edge, 5 ns; impulse duration, 200 ns. The unconventional approach is that the plates must be replaced by a set of cylinders. The obtained magnet construction enables the field homogeneity to be controlled by changing current magnitudes in cylinders. Furthermore, we demonstrated the method of field optimization. In addition, measurement technique for the harmonic components was considered and the possibility of control harmonic components value was demonstrated.

Forward transformation for high resolution eddy current tomography using whitney elements

International Nuclear Information System (INIS)

Szewczyk, R.; Salach, J.; Nowicki, M.; Ruokolainen, J.; Raback, P.

2014-01-01

Tomographic methods are intensively developed field of non-destructive testing. The main advantage of this type of NDT method is 3D information concerning the shape of the discontinuities in investigated material. On the other hand, the most common tomography method utilizing X-rays creates the significant risks typical to X-ray technique. As a result, Xray tomography is difficult to use in industry. Introduced to the industry in 2007, the eddy current tomography is safe and cost effective. However, in opposite to X-ray tomography, eddy current tomography requires sophisticated and time consuming inverse transformation creating 2D or 3D view of discontinuities. For this reason solutions presented previously are focused on 2D inverse transformation and exhibit limited resolution. For eddy current tomography, the forward tomographic transformation is most important, which is the base of inverse transformation. This paper presents the novel, fast and cost-effective solution utilizing Whitney elements method for such forward transformation. As a result, new possibilities of development in the area of high resolution 3D eddy current tomography are created. (authors)

Seizure-induced alterations in fast-spiking basket cell GABA currents modulate frequency and coherence of gamma oscillation in network simulations

Energy Technology Data Exchange (ETDEWEB)

Proddutur, Archana; Yu, Jiandong; Elgammal, Fatima S. [Department of Neurology and Neurosciences, New Jersey Medical School, Rutgers, Newark, New Jersey 07103 (United States); Santhakumar, Vijayalakshmi, E-mail: santhavi@njms.rutgers.edu [Department of Neurology and Neurosciences, New Jersey Medical School, Rutgers, Newark, New Jersey 07103 (United States); Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, Newark, New Jersey 07103 (United States)

2013-12-15

Gamma frequency oscillations have been proposed to contribute to memory formation and retrieval. Fast-spiking basket cells (FS-BCs) are known to underlie development of gamma oscillations. Fast, high amplitude GABA synapses and gap junctions have been suggested to contribute to gamma oscillations in FS-BC networks. Recently, we identified that, apart from GABAergic synapses, FS-BCs in the hippocampal dentate gyrus have GABAergic currents mediated by extrasynaptic receptors. Our experimental studies demonstrated two specific changes in FS-BC GABA currents following experimental seizures [Yu et al., J. Neurophysiol. 109, 1746 (2013)]: increase in the magnitude of extrasynaptic (tonic) GABA currents and a depolarizing shift in GABA reversal potential (E{sub GABA}). Here, we use homogeneous networks of a biophysically based model of FS-BCs to examine how the presence of extrasynaptic GABA conductance (g{sub GABA-extra}) and experimentally identified, seizure-induced changes in g{sub GABA-extra} and E{sub GABA} influence network activity. Networks of FS-BCs interconnected by fast GABAergic synapses developed synchronous firing in the dentate gamma frequency range (40–100 Hz). Systematic investigation revealed that the biologically realistic range of 30 to 40 connections between FS-BCs resulted in greater coherence in the gamma frequency range when networks were activated by Poisson-distributed dendritic synaptic inputs rather than by homogeneous somatic current injections, which were balanced for FS-BC firing frequency in unconnected networks. Distance-dependent conduction delay enhanced coherence in networks with 30–40 FS-BC interconnections while inclusion of gap junctional conductance had a modest effect on coherence. In networks activated by somatic current injections resulting in heterogeneous FS-BC firing, increasing g{sub GABA-extra} reduced the frequency and coherence of FS-BC firing when E{sub GABA} was shunting (−74 mV), but failed to alter average

Creation of excitations and defects in insulating materials by high-current-density electron beams of nanosecond pulse duration

International Nuclear Information System (INIS)

Vaisburd, D.I.; Evdokimov, K.E.

2005-01-01

The paper is concerned with fast and ultra-fast processes in insulating materials under the irradiation by a high-current-density electron beam of a nanosecond pulse duration. The inflation process induced by the interaction of a high-intensity electron beam with a dielectric is examined. The ''instantaneous'' distribution of non-ionizing electrons and holes is one of the most important stages of the process. Ionization-passive electrons and holes make the main contribution to many fast processes with a characteristic time in the range 10 -14 /10 -12 s: high-energy conductivity, intraband luminescence, etc. A technique was developed for calculation of the ''instantaneous'' distribution of non-ionizing electrons and holes in a dielectric prior to electron-phonon relaxation. The following experimental effects are considered: intraband luminescence, coexistence of intraband electron luminescence and band-to-band hole luminescence in CsI, high energy conductivity; generation of mechanical fields and their interaction with cracks and dislocations. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Feasibility study on commercialized fast reactor cycle systems. (1) Current status of the phase-II study

International Nuclear Information System (INIS)

Sagayama, Yutaka

2005-01-01

A feasibility study on commercialized fast reactors including related nuclear fuel cycle systems has been started from Japanese fiscal year 1999 by a Japanese joint project team of Japan Nuclear Cycle Development Institute and the Japan Atomic Power Company. This project aims at elucidating prominent fast reactor cycle systems that will respond to various needs of society in the future, together with economic competitiveness as future electricity supply systems. Challenging technology goals for the fast reactor cycle systems were defined in five targets: safety, economic competitiveness, reduction of environmental burden, efficient utilization of nuclear fuel resources and enhancement of nuclear non-proliferation. As the results of the feasibility study up to now, it is confirmed as the interim results that the combination of sodium-cooled fast reactors with oxide fuels, advanced aqueous reprocessing and simplified pellet fuel fabrication is highly suited to the development targets. The cost would be highly reduced by the adoption of innovative technologies, which feasibility is relatively clear and some R and D issues are now under progress. (author)

Current status of fast reactor physics

International Nuclear Information System (INIS)

Hummel, H.H.

1979-01-01

The subject of calculation of reactivity coefficients for fast reactors is developed, starting with a discussion of the status of relevant nuclear data and proceeding to the subjects of group cross section generation and of methods of obtaining reactivity coefficients from group cross sections. Reactivity coefficients measured in critical experiments are compared with calculated values. Dependence of reactivity coefficients on reactor design is discussed. Finally, results of the recent international comparison of calculated reactivity coefficients are presented

Fast pyrolysis of biomass at high temperatures

DEFF Research Database (Denmark)

Trubetskaya, Anna

This Ph.D. thesis describes experimental and modeling investigations of fast high temperature pyrolysis of biomass. Suspension firing of biomass is widely used for power generation and has been considered as an important step in reduction of greenhouse gas emissions by using less fossil fuels. Fast...... to investigate the effects of operating parameters and biomass types on yields of char and soot, their chemistry and morphology as well as their reactivity using thermogravimetric analysis. The experimental study was focused on the influence of a wide range of operating parameters including heat treatment...... alkali metals. In this study, potassium lean pinewood (0.06 wt. %) produced the highest soot yield (9 and 7 wt. %) at 1250 and 1400°C, whereas leached wheat straw with the higher potassium content (0.3 wt. %) generated the lowest soot yield (2 and 1 wt. %). Soot yields of wheat and alfalfa straw at both...

Device and method for relativistic electron beam heating of a high-density plasma to drive fast liners

International Nuclear Information System (INIS)

Thode, L.E.

1981-01-01

A device and method for relativistic electron beam heating of a high-density plasma in a small localized region are described. A relativistic electron beam generator or accelerator produces a high-voltage electron beam which propagates along a vacuum drift tube and is modulated to initiate electron bunching within the beam. The beam is then directed through a low-density gas chamber which provides isolation between the vacuum modulator and the relativistic electron beam target. The relativistic beam is then applied to a high-density target plasma which typically comprises dt, dd, hydrogen boron or similar thermonuclear gas at a density of 1017 to 1020 electrons per cubic centimeter. The target gas is ionized prior to application of the electron beam by means of a laser or other preionization source to form a plasma. Utilizing a relativistic electron beam with an individual particle energy exceeding 3 mev, classical scattering by relativistic electrons passing through isolation foils is negligible. As a result, relativistic streaming instabilities are initiated within the high-density target plasma causing the relativistic electron beam to efficiently deposit its energy and momentum into a small localized region of the high-density plasma target. Fast liners disposed in the high-density target plasma are explosively or ablatively driven to implosion by a heated annular plasma surrounding the fast liner which is generated by an annular relativistic electron beam. An azimuthal magnetic field produced by axial current flow in the annular plasma, causes the energy in the heated annular plasma to converge on the fast liner

Fast turn-off of high voltage 4H–SiC npn BJTs from the saturation on-state regime

International Nuclear Information System (INIS)

Ivanov, P A; Levinshtein, M E; Palmour, J W; Agarwal, A K; Zhang, J

2010-01-01

Fast turn-off of high-voltage (breakdown voltage ≥ 3 kV) 4H–SiC npn bipolar junction transistors driven in a deeply saturated regime has been reported. In the conventional turn-off mode (base current break), the turn-off delay and current fall times are 80 ns and 100 ns, respectively. It is shown that these times can be made as short as 20 and 4 ns, respectively, if a reverse base current pulse of appropriate amplitude is applied to sweep out minority carriers from the base. The experimental values of delay and turn-off times well coincide with those calculated in terms of the charge control model

High-Average, High-Peak Current Injector Design

CERN Document Server

Biedron, S G; Virgo, M

2005-01-01

There is increasing interest in high-average-power (>100 kW), um-range FELs. These machines require high peak current (~1 kA), modest transverse emittance, and beam energies of ~100 MeV. High average currents (~1 A) place additional constraints on the design of the injector. We present a design for an injector intended to produce the required peak currents at the injector, eliminating the need for magnetic compression within the linac. This reduces the potential for beam quality degradation due to CSR and space charge effects within magnetic chicanes.

Fast T1 mapping of the brain at high field using Look-Locker and fast imaging.

Science.gov (United States)

Jiang, Ke; Zhu, Yanjie; Jia, Sen; Wu, Yin; Liu, Xin; Chung, Yiu-Cho

2017-02-01

This study aims to develop and evaluate a new method for fast high resolution T1 mapping of the brain based on the Look-Locker technique. Single-shot turboflash sequence with high temporal acceleration is used to sample the recovery of inverted magnetization. Multi-slice interleaved acquisition within one inversion slab is used to reduce the number of inversion pulses and hence SAR. Accuracy of the proposed method was studied using simulation and validated in phantoms. It was then evaluated in healthy volunteers and stroke patients. In-vivo results were compared to values obtained by inversion recovery fast spin echo (IR-FSE) and literatures. With the new method, T 1 values in phantom experiments agreed with reference values with median error map was acquired in 3.35s and the T1 maps of the whole brain were acquired in 2min with two-slice interleaving, with a spatial resolution of 1.1×1.1×4mm 3 . The T 1 values obtained were comparable to those measured with IR-FSE and those reported in literatures. These results demonstrated the feasibility of the proposed method for fast T1 mapping of the brain in both healthy volunteers and stroke patients at 3T. Copyright © 2016 Elsevier Inc. All rights reserved.

High-density and high-ρR fuel assembly for fast-ignition inertial confinement fusion

International Nuclear Information System (INIS)

Betti, R.; Zhou, C.

2005-01-01

Scaling relations to optimize implosion parameters for fast-ignition inertial confinement fusion are derived and used to design high-gain fast-ignition targets. A method to assemble thermonuclear fuel at high densities, high ρR, and with a small-size hot spot is presented. Massive cryogenic shells can be imploded with a low implosion velocity V I on a low adiabat α using the relaxation-pulse technique. While the low V I yields a small hot spot, the low α leads to large peak values of the density and areal density. It is shown that a 750 kJ laser can assemble fuel with V I ≅1.7x10 7 cm/s, α≅0.7, ρ≅400 g/cc, ρR≅3 g/cm 2 , and a hot-spot volume of less than 10% of the compressed core. If fully ignited, this fuel assembly can produce high gains of interest to inertial fusion energy applications

High PRF high current switch

Science.gov (United States)

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.

Fast ion confinement during high power tangential neutral beam injection into low plasma current discharges on the ISX-B tokamak

International Nuclear Information System (INIS)

Carnevali, A.; Scott, S.D.; Neilson, H.; Galloway, M.; Stevens, P.; Thomas, C.E.

1988-01-01

The beam ion thermalization process during tangential neutral beam injection in the ISX-B tokamak is investigated. The classical model is tested in co- and counter-injected discharges at low plasma current, a regime where large orbit width excursions enhance the importance of the loss regions. To test the model, experimental charge exchange spectra are compared with the predictions of an orbit following Monte Carlo code. Measurements of beam-plasma neutron emission and measured decay rates of the emission following beam turnoff provide additional information. Good agreement is found between theory and experiment. Furthermore, beam additivity experiments show that, globally, the confinement of beam ions remains classical, independently of the injected beam power. However, some experimental evidence suggests that the fast ion density in the plasma core did not increase with beam power in a way consistent with classical processes. (author). 35 refs, 17 figs, 3 tabs

Application of Electron Bernstein Wave heating and current drive to high beta plasmas

International Nuclear Information System (INIS)

Efthimion, P.C.

2002-01-01

Electron Bernstein Waves (EBW) can potentially heat and drive current in high-beta plasmas. Electromagnetic waves can convert to EBW via two paths. O-mode heating, demonstrated on W-7AS, requires waves be launched within a narrow k-parallel range. Alternately, in high-beta plasmas, the X-mode cutoff and EBW conversion layers are millimeters apart, so the fast X-mode can tunnel to the EBW branch. We are studying the conversion of EBW to the X-mode by measuring the radiation temperature of the cyclotron emission and comparing it to the electron temperature. In addition, mode conversion has been studied with an approximate kinetic full-wave code. We have enhanced EBW mode conversion to ∼ 100% by encircling the antenna with a limiter that shortens the density scale length at the conversion layer in the scrape off of the CDX-U spherical torus (ST) plasma. Consequently, a limiter in front of a launch antenna achieves efficient X-mode coupling to EBW. Ray tracing and Fokker-Planck codes have been used to develop current drive scenarios in NSTX high-beta (∼ 40%) ST plasmas and a relativistic code will examine the potential synergy of EBW current drive with the bootstrap current. (author)

Development of a fast voltage control method for electrostatic accelerators

International Nuclear Information System (INIS)

Lobanov, Nikolai R.; Linardakis, Peter; Tsifakis, Dimitrios

2014-01-01

The concept of a novel fast voltage control loop for tandem electrostatic accelerators is described. This control loop utilises high-frequency components of the ion beam current intercepted by the image slits to generate a correction voltage that is applied to the first few gaps of the low- and high-energy acceleration tubes adjoining the high voltage terminal. New techniques for the direct measurement of the transfer function of an ultra-high impedance structure, such as an electrostatic accelerator, have been developed. For the first time, the transfer function for the fast feedback loop has been measured directly. Slow voltage variations are stabilised with common corona control loop and the relationship between transfer functions for the slow and new fast control loops required for optimum operation is discussed. The main source of terminal voltage instabilities, which are due to variation of the charging current caused by mechanical oscillations of charging chains, has been analysed

Status of national programmes on fast reactors

International Nuclear Information System (INIS)

1994-04-01

Based on the International Working Group on Fast reactors (IWGFR) members' request, the IAEA organized a special meeting on Fast Reactor Development and the Role of the IAEA in May 1993. The purpose of the meeting was to review and discuss the status and recent development, to present major changes in fast reactor programmes and to recommend future activities on fast reactors. The IWGFR took note that in some Member States large prototypes have been built or are under construction. However, some countries, due to their current budget constraints, have reduced the level of funding for research and development programmes on fast reactors. The IWGFR noted that in this situation the international exchange of information and cooperation on the development of fast reactors is highly desirable and stressed the importance of the IAEA's programme on fast reactors. These proceedings contain important and useful information on national programmes and new developments in sodium cooled fast reactors in Member States. Refs, figs and tabs

An analysis of JET fast-wave heating and current drive experiments directly related to ITER

Energy Technology Data Exchange (ETDEWEB)

Bhatnagar, V P; Eriksson, L; Gormezano, C; Jacquinot, J; Kaye, A; Start, D F.H. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking

1994-07-01

The ITER fast-wave system is required to serve a variety of purposes, in particular, plasma heating to ignition, current profile and burn control and eventually, in conjunction with other schemes, a central non-inductive current drive (CD) for the steady-state operation of ITER. The ICRF heating and current drive data that has been obtained in JET are analyzed in terms of dimensionless parameters, with a view to ascertaining its direct relevance to key ITER requirements. The analysis is then used to identify areas both in physics and technological aspects of ion-cyclotron resonance heating (ICRH) and CD that require further experimentation in ITER-relevant devices such as JET to establish the required data base. (authors). 12 refs., 8 figs.

An analysis of JET fast-wave heating and current drive experiments directly related to ITER

International Nuclear Information System (INIS)

Bhatnagar, V.P.; Eriksson, L.; Gormezano, C.; Jacquinot, J.; Kaye, A.; Start, D.F.H.

1994-01-01

The ITER fast-wave system is required to serve a variety of purposes, in particular, plasma heating to ignition, current profile and burn control and eventually, in conjunction with other schemes, a central non-inductive current drive (CD) for the steady-state operation of ITER. The ICRF heating and current drive data that has been obtained in JET are analyzed in terms of dimensionless parameters, with a view to ascertaining its direct relevance to key ITER requirements. The analysis is then used to identify areas both in physics and technological aspects of ion-cyclotron resonance heating (ICRH) and CD that require further experimentation in ITER-relevant devices such as JET to establish the required data base. (authors). 12 refs., 8 figs

Low power fast settling multi-standard current reusing CMOS fractional-N frequency synthesizer

International Nuclear Information System (INIS)

Lou Wenfeng; Feng Peng; Wang Haiyong; Wu Nanjian

2012-01-01

A low power fast settling multi-standard CMOS fractional-N frequency synthesizer is proposed. The current reusing and frequency presetting techniques are adopted to realize the low power fast settling multi-standard fractional-N frequency synthesizer. An auxiliary non-volatile memory (NVM) is embedded to avoid the repetitive calibration process and to save power in practical application. This PLL is implemented in a 0.18 μm technology. The frequency range is 0.3 to 2.54 GHz and the settling time is less than 5 μs over the entire frequency range. The LC-VCO with the stacked divide-by-2 has a good figure of merit of −193.5 dBc/Hz. The measured phase noise of frequency synthesizer is about −115 dBc/Hz at 1 MHz offset when the carrier frequency is 2.4 GHz and the reference spurs are less than −52 dBc. The whole frequency synthesizer consumes only 4.35 mA and 1.8 V. (semiconductor integrated circuits)

Microwave testing of high-Tc based direct current to a single flux quantum converter

DEFF Research Database (Denmark)

Kaplunenko, V. K.; Fischer, Gerd Michael; Ivanov, Z. G.

1994-01-01

Design, simulation, and experimental investigations of a direct current to a single flux quantum converter loaded with a Josephson transmission line and driven by an external 70 GHz microwave oscillator are reported. The test circuit includes nine YBaCuO Josephson junctions aligned on the grain...... boundary of a 0°–32° asymmetric Y-ZrO2 bicrystal substrate. The performance of such converters is important for the development of the fast Josephson samplers required for testing of high-Tc rapid single flux quantum circuits in high-speed digital superconducting electronics. Journal of Applied Physics...

Low fasting low high-density lipoprotein and postprandial lipemia

Directory of Open Access Journals (Sweden)

Sorodila Konstandina

2004-07-01

Full Text Available Abstract Background Low levels of high density lipoprotein (HDL cholesterol and disturbed postprandial lipemia are associated with coronary heart disease. In the present study, we evaluated the variation of triglyceride (TG postprandially in respect to serum HDL cholesterol levels. Results Fifty two Greek men were divided into 2 main groups: a the low HDL group (HDL p = 0.002. The low HDL group had significantly higher TG at 4, 6 and 8 h postprandially compared to the controls (p = 0.006, p = 0.002, and p p = 0.017 compared to the matched-control group. ROC analysis showed that fasting TG ≥ 121 mg/dl have 100% sensitivity and 81% specificity for an abnormal TG response (auc = 0.962, p Conclusions The delayed TG clearance postprandially seems to result in low HDL cholesterol even in subjects with low fasting TG. The fasting TG > 121 mg/dl are predictable for abnormal response to fatty meal.

The physics of fast Z pinches

International Nuclear Information System (INIS)

Ryutov, D.D.; Derzon, M.S.; Matzen, M.K.

1998-07-01

The spectacular progress made during the last few years in reaching high energy densities in fast implosions of annular current sheaths (fast Z pinches) opens new possibilities for a broad spectrum of experiments, from x-ray generation to controlled thermonuclear fusion and astrophysics. Presently Z pinches are the most intense laboratory X ray sources (1.8 MJ in 5 ns from a volume 2 mm in diameter and 2 cm tall). Powers in excess of 200 TW have been obtained. This warrants summarizes the present knowledge of physics that governs the behavior of radiating current-carrying plasma in fast Z-pinches. This survey covers essentially all aspects of the physics of fast Z pinches: initiation, instabilities of the early stage, magnetic Rayleigh-Taylor instability in the implosion phase, formation of a transient quasi-equilibrium near the stagnation point, and rebound. Considerable attention is paid to the analysis of hydrodynamic instabilities governing the implosion symmetry. Possible ways of mitigating these instabilities are discussed. Non-magnetohydrodynamic effects (anomalous resistivity, generation of particle beams, etc.) are summarized. Various applications of fast Z pinches are briefly described. Scaling laws governing development of more powerful Z pinches are presented. The survey contains 52 figures and nearly 300 references

The Physics of Fast Z Pinches

Energy Technology Data Exchange (ETDEWEB)

RYUTOV,D.D.; DERZON,MARK S.; MATZEN,M. KEITH

1999-10-25

The spectacular progress made during the last few years in reaching high energy densities in fast implosions of annular current sheaths (fast Z pinches) opens new possibilities for a broad spectrum of experiments, from x-ray generation to controlled thermonuclear fusion and astrophysics. Presently Z pinches are the most intense laboratory X ray sources (1.8 MJ in 5 ns from a volume 2 mm in diameter and 2 cm tall). Powers in excess of 200 TW have been obtained. This warrants summarizing the present knowledge of physics that governs the behavior of radiating current-carrying plasma in fast Z pinches. This survey covers essentially all aspects of the physics of fast Z pinches: initiation, instabilities of the early stage, magnetic Rayleigh-Taylor instability in the implosion phase, formation of a transient quasi-equilibrium near the stagnation point, and rebound. Considerable attention is paid to the analysis of hydrodynamic instabilities governing the implosion symmetry. Possible ways of mitigating these instabilities are discussed. Non-magnetohydrodynamic effects (anomalous resistivity, generation of particle beams, etc.) are summarized. Various applications of fast Z pinches are briefly described. Scaling laws governing development of more powerful Z pinches are presented. The survey contains 36 figures and more than 300 references.

High current plasma electron emitter

International Nuclear Information System (INIS)

Fiksel, G.; Almagri, A.F.; Craig, D.

1995-07-01

A high current plasma electron emitter based on a miniature plasma source has been developed. The emitting plasma is created by a pulsed high current gas discharge. The electron emission current is 1 kA at 300 V at the pulse duration of 10 ms. The prototype injector described in this paper will be used for a 20 kA electrostatic current injection experiment in the Madison Symmetric Torus (MST) reversed-field pinch. The source will be replicated in order to attain this total current requirement. The source has a simple design and has proven very reliable in operation. A high emission current, small size (3.7 cm in diameter), and low impurity generation make the source suitable for a variety of fusion and technological applications

Commissioning of the long-pulse fast wave current drive antennas for DIII-D

International Nuclear Information System (INIS)

Baity, F.W.; Barber, G.C.; Goulding, R.H.; Hoffman, D.J.; DeGrassie, J.S.; Pinsker, R.I.; Petty, C.C.; Cary, W.

1995-01-01

Two new four-element fast wave current drive antennas have been installed on DIII-D. These antennas are designed for 10-s pulses at 2 MW each in the frequency range of 30 to 120 MHz. Each element comprises two poloidal segments fed in parallel in order to optimize plasma coupling at the upper end of the frequency range. The antennas are mounted on opposite sides of the vacuum vessel, in ports designated 0 degrees and 180 degrees after their toroidal angle. Each antenna array is fed by a single transmitter. The power is first split two ways by means of a 3-dB hybrid coupler, then each of these lines feeds a resonant loop connecting a pair of array elements. The power transfer during asymmetric phasing is shunted between resonant loops by a decoupler. The resonant loops are fitted with line stretchers so that multiple frequencies of operation are possible without reconfiguring the transmission line. Commissioning of these antennas has been underway since June 1994. Several deficiencies in the transmission line system were uncovered during initial vacuum conditioning, including problems with the transmission line insulators and with the drive rods for the variable elements. The former was solved by replacing the original alumina insulators, and the latter has been avoided during operation to date by positioning the tuners to avoid high voltage appearing on the drive rods. A modified design for the drive rods will be implemented before RF operations resume operation June 1995. New transmitters were procured from ABB for the new antennas and were installed in parallel with the antenna installation. During initial vacuum conditioning of the antenna in the 180 degree port a fast digital oscilloscope was used to try to pinpoint the location of arcing by a time-of-flight technique and to develop an understanding of the typical arc signature in the system

Remote field eddy current testing for steam generator inspection of fast reactor

Energy Technology Data Exchange (ETDEWEB)

Kobayashi, Noriyasu, E-mail: noriyasu.kobayashi@toshiba.co.jp [Power and Industrial Systems Research and Development Center, Toshiba Corporation, 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8523 (Japan); Ueno, Souichi; Nagai, Satoshi; Ochiai, Makoto [Power and Industrial Systems Research and Development Center, Toshiba Corporation, 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8523 (Japan); Jimbo, Noboru [Isogo Nuclear Engineering Center, Toshiba Corporation, 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8523 (Japan)

2011-12-15

Highlights: Black-Right-Pointing-Pointer We confirmed defect detection performances of remote field eddy current testing. Black-Right-Pointing-Pointer It is difficult to inspect outer surface of double wall tube steam generator. Black-Right-Pointing-Pointer We used coils with flux guide made of iron-nickel alloy for high sensitivity. Black-Right-Pointing-Pointer Output voltage of detector coil increased more than 100 times. Black-Right-Pointing-Pointer We were able to detect small hole defect of 1mm in diameter on outer surface. - Abstract: We confirmed the defect detection performances of the remote field eddy current testing (RFECT) in order to inspect the helical-coil-type double wall tube steam generator (DWTSG) with the wire mesh layer for the new small fast reactor 4S (Super-Safe, Small and Simple). As the high sensitivity techniques, we tried to increase the direct magnetic field intensity in the vicinity of the inner wall of the tube and decrease the direct magnetic field around the central axis of the tube using the exciter coil with the flux guide made of the iron-nickel alloy. We adopted the horizontal type multiple detector coils with the flux guides arrayed circumferentially to enhance the sensitivity of the radial component. According to the experimental results, the output voltage of the detector coil in the region of indirect magnetic field increased more than 100 times by the application of the exciter and detector coils with the flux guides. Finally, we were able to detect the small hole defect of 1 mm in diameter and 20% of the outer tube thickness in depth over the wire mesh layer by the adoption of the exciter coil and horizontal type multiple detector coils with the flux guides. We also confirmed that the RFECT probe is useful for detecting thinning defects. These experimental results indicated that there is the possibility that we can inspect the double wall tube with the wire mesh layer using the RFECT.

Recent Developments in High-Harmonic Fast Wave Physics in NSTX

International Nuclear Information System (INIS)

LeBlanc, B.P.; Bell, R.E.; Bonoli, P.; Harvey, R.; Heidbrink, W.W.; Hosea, J.C.; Kaye, S.M.; Liu, D.; Maingi, R.; Medley, S.S.; Ono, M.; Podesta, M.; Phillips, C.K.; Ryan, P.M.; Roquemore, A.L.; Taylor, G.; Wilson, J.R.

2010-01-01

Understanding the interaction between ion cyclotron range of frequency (ICRF) fast waves and the fast-ions created by neutral beam injection (NBI) is critical for future devices such as ITER, which rely on a combination ICRF and NBI. Experiments in NSTX which use 30 MHz High-Harmonic Fast-Wave (HHFW) ICRF and NBI heating show a competition between electron heating via Landau damping and transit-time magnetic pumping, and radio-frequency wave acceleration of NBI generated fast ions. Understanding and mitigating some of the power loss mechanisms outside the last closed flux surface (LCFS) has resulted in improved HHFW heating inside the LCFS. Nevertheless a significant fraction of the HHFW power is diverted away from the enclosed plasma. Part of this power is observed locally on the divertor. Experimental observations point toward the radio-frequency (RF) excitation of surface waves, which disperse wave power outside the LCFS, as a leading loss mechanism. Lithium coatings lower the density at the antenna, thereby moving the critical density for perpendicular fast-wave propagation away from the antenna and surrounding material surfaces. Visible and infrared imaging reveal flows of RF power along open field lines into the divertor region. In L-mode -- low average NBI power -- conditions, the fast-ion D-alpha (FIDA) diagnostic measures a near doubling and broadening of the density profile of the upper energetic level of the fast ions concurrent with the presence of HHFW power launched with k// = -8m-1. We are able to heat NBI-induced H-mode plasmas with HHFW. The captured power is expected to be split between absorption by the electrons and absorption by the fast ions, based on TORIC calculation. In the case discussed here the Te increases over the whole profile when ∼2MW of HHFW power with antenna k// = 13m-1 is applied after the H-mode transition. But somewhat unexpectedly fast-ion diagnostics do not observe a change between the HHFW heated NBI discharge and the

High-Sensitivity Fast Neutron Detector KNK-2-8M

Science.gov (United States)

Koshelev, A. S.; Dovbysh, L. Ye.; Ovchinnikov, M. A.; Pikulina, G. N.; Drozdov, Yu. M.; Chuklyaev, S. V.; Pepyolyshev, Yu. N.

2017-12-01

The design of the fast neutron detector KNK-2-8M is outlined. The results of he detector study in the pulse counting mode with pulses from 238U nuclei fission in the radiator of the neutron-sensitive section and in the current mode with separation of functional section currents are presented. The possibilities of determination of the effective number of 238U nuclei in the radiator of the neutron-sensitive section are considered. The diagnostic capabilities of the detector in the counting mode are demonstrated, as exemplified by the analysis of reference data on characteristics of neutron fields in the BR-1 reactor hall. The diagnostic capabilities of the detector in the current mode are demonstrated, as exemplified by the results of measurements of 238U fission intensity in the power startup of the BR-K1 reactor in the fission pulse generation mode with delayed neutrons and the detector placed in the reactor cavity in conditions of large-scale variation of the reactor radiation fields.

Application of high speed photography for high current vacuum arcs

NARCIS (Netherlands)

Damstra, G.C.; Merck, W.F.H.; Vossen, J.W.G.L.; Janssen, M.F.P.; Bouwmeester, C.E.

1998-01-01

A high speed image detection system for 106 frames per second or 107 streaks per second has been developed for the testing of vacuum circuit breakers, using 10×16 optical fibres for light transfer to 160 fast photo diodes. The output of these diodes is multiplexed, AD converted in a 4 bit

Technical Meeting on Impact of Fukushima Event on Current and Future Fast Reactor Designs. Presentations

International Nuclear Information System (INIS)

2012-01-01

The overall purpose of the Technical Meeting was to recognize and analyse the implications of the accident occurred at the Fukushima Dai-ichi Nuclear Power Station on current and future fast neutron systems design and operation. The aim was to provide a global forum for discussing the principal lessons learned from this event, and thus to review safety principles and characteristics of existing and future fast neutron concepts, especially in relation with extreme natural events which potentially may lead to severe accident scenarios. The participants also presented and discussed innovative technical solutions, design features and countermeasures for design extension conditions - including earthquakes, tsunami and other extreme natural hazards - which can enhance the safety level of existing and future fast neutron systems. Furthermore, the meeting gave the opportunity to present advanced methods for the evaluation of the robustness of plants against design extension conditions. Another important goal of this TM was to discuss how to harmonize safety approaches and goals for next generation’s fast reactors. Finally, the meeting was intended to identify areas where further research and development in nuclear safety, technology and engineering in the light of the Fukushima accident are needed. In the frame of the implementation of its Nuclear Safety Action Plan endorsed by all Member States, the IAEA will consider these areas as potential technical topics for new Coordinated Research Projects, to be launched in the near future

The Association between Socio-Demographic Charactristics and Fast Food Consumption withinHigh School Students in Isfahan, Iran

Directory of Open Access Journals (Sweden)

Parastoo Yarmohammadi

2015-12-01

Full Text Available Abstract Introduction: Fast food consumption has greatly increased with in adolescents in recent years, which is linked with weight gain, poor dietary indexes and insulin resistance. Hence, the purpose of this study was to examine the association between demographic characteristics and fast food consumption with in high school students. Materials & Methods: In this descriptive-analytic study, a sample of 521 high school students  aged 15-18 years were examined in Isfahan city, who were selected via multistage sampling method. The study data were collected using a questionnaire completed by the students. The present study probed to assess such items as frequency of fast food consumption, demographic characteristics, hours of television viewing, as well as high school students' knowledge and attitude. The collected data were analyzed using descriptive and inferential statistics. Result: Frequent intake of fast food (&ge1 time/week was reported 15.5% within females and 15.3% within males. A significant relationship was detected between parents’ high level of education and high income of the family with the fast food consumption. The predominate reasons for fast food consumption were stated as “enjoying tastes”, “eating at any place”,” inexpensive and economic”. Conclusion: The findings revealed that fast food consumption increased in families with high income and high education level, though these families needed to be educated on the harmful effects of fast food and how to choose the healthy foods. Therefore, some interventions may be regarded beneficial in order to reduce the exposure to the fast food and promote knowledge, attitude, and behavior change in regard with reducing consumption of fast food.

Development of a fast rise-time, high-voltage pulse generator

International Nuclear Information System (INIS)

Zhang Yanxia; Zhu Jie; Li Xianyou

2006-01-01

In order to test the attenuation of the system, a fast rise-time, high-voltage pulse generator is required for the fast pulse signal measurement. The paper presents the development of the generator. More emphasis is paid on the discussion of the difficulties occurring in the circuit debugging and their resolutions. The output rise-time of the generator is 700 ps, the amplitude is adjustable in the range of 0 to 500 V, the pulse-width is adjustable in the range of 4ns to 1μs. (authors)

The economics of fast charging infrastructure for electric vehicles

International Nuclear Information System (INIS)

Schroeder, Andreas; Traber, Thure

2012-01-01

By 2011 little is known about the economic rationale of public fast chargers for electric vehicles (EV). This paper aims at providing an insight into the business case of this technology in a case study for Germany. The estimated Return on Investment (ROI) of a public fast charging station constitutes the main contribution. Potential users and organization structures are investigated as well as different tariff types. According to the estimations, the current market outlook seems too uncertain for triggering a large-scale roll-out of fast charging infrastructure. Approximations suggest that investment is hardly profitable at low EV adoption rates, unless investment cost can be severely lowered. Besides competition with alternative charging solutions, the general EV adoption rate is detected as being a main risk factor for investment in public charging infrastructure. Highlights: ► Private investment into public fast charging infrastructure appears to be driven by other than pure project prospects at current EV penetration rates. ► High cost markups are needed to refinance investment, unless grid tariffs are exempted or constant high demand is assured. ► Investment into public fast charging remains risky and incentives can be contained by the spreading of alternative home-charging devices and alternative propulsion technologies.

A Fast General-Purpose Clustering Algorithm Based on FPGAs for High-Throughput Data Processing

CERN Document Server

Annovi, A; The ATLAS collaboration; Castegnaro, A; Gatta, M

2012-01-01

We present a fast general-purpose algorithm for high-throughput clustering of data ”with a two dimensional organization”. The algorithm is designed to be implemented with FPGAs or custom electronics. The key feature is a processing time that scales linearly with the amount of data to be processed. This means that clustering can be performed in pipeline with the readout, without suffering from combinatorial delays due to looping multiple times through all the data. This feature makes this algorithm especially well suited for problems where the data has high density, e.g. in the case of tracking devices working under high-luminosity condition such as those of LHC or Super-LHC. The algorithm is organized in two steps: the first step (core) clusters the data; the second step analyzes each cluster of data to extract the desired information. The current algorithm is developed as a clustering device for modern high-energy physics pixel detectors. However, the algorithm has much broader field of applications. In ...

Fast-opening vacuum switches for high-power inductive energy storage

International Nuclear Information System (INIS)

Cooperstein, G.

1988-01-01

The subject of fast-opening vacuum switches for high-power inductive energy storage is emerging as an exciting new area of plasma science research. This opening switch technology, which generally involves the use of plasmas as the switching medium, is key to the development of inductive energy storage techniques for pulsed power which have a number of advantages over conventional capacitive techniques with regard to cost and size. This paper reviews the state of the art in this area with emphasis on applications to inductive storage pulsed power generators. Discussion focuses on fast-opening vacuum switches capable of operating at high power (≥10 12 W). These include plasma erosion opening switches, ion beam opening switches, plasma filled diodes, reflex diodes, plasma flow switches, and other novel vacuum opening switches

Profile Modifications Resulting from Early High-harmonic Fast Wave heating in NSTX

International Nuclear Information System (INIS)

Mendard, J.E.; LeBlanc, Wilson J.R.; Sabbagh, S.A.; Stutman, D.; Swain, D.W.

2001-01-01

Experiments have been performed in the National Spherical Torus Experiment (NSTX) to inject high harmonic fast wave (HHFW) power early during the plasma current ramp-up in an attempt to reduce the current penetration rate to raise the central safety factor during the flattop phase of the discharge. To date, up to 2 MW of HHFW power has been coupled to deuterium plasmas as early as t = 50 ms using the slowest interstrap phasing of k|| approximately equals 14 m(superscript)-1 (nf = 24). Antenna-plasma gap scans have been performed and find that for small gaps (5-8 cm), electron heating is observed with relatively small density rises and modest reductions in current penetration rate. For somewhat larger gaps (10-12 cm), weak electron heating is observed but with a spontaneous density rise at the plasma edge similar to that observed in NSTX H-modes. In the larger gap configuration, EFIT code reconstructions (without MSE [motional Stark effect]) find that resistive flux consumption is reduced as much as 30%, the internal inductance is maintained below 0.6 at 1 MA into the flattop, q(0) is increased significantly, and the MHD stability character of the discharges is strongly modified

Z a Fast Pulsed Power Generator for Ultra-High Magnetic Field Generation

Science.gov (United States)

Spielman, R. B.; Stygar, W. A.; Struve, K. W.; Asay, J. R.; Hall, C. A.; Bernard, M. A.; Bailey, J. E.; McDaniel, D. H.

2004-11-01

Advances in fast, pulsed-power technologies have resulted in the development of very high current drivers that have current rise times ~100 ns. The largest such pulsed power driver today is the new Z accelerator located at Sandia National Laboratories in Albuquerque, New Mexico. Z can deliver more than 20 MA with a time-to-peak of 105 ns to low inductance (~1 nH) loads. Such large drivers are capable of directly generating magnetic fields approaching 3 kT in small, 1 cm3 volumes. In addition to direct field generation, Z can be used to compress an applied, axial seed field with a plasma. Flux compression schemes are not new and are, in fact, the basis of all explosive flux-compression generators, but we propose the use of plasma armatures rather than solid, conducting armatures. We present experimental results from the Z accelerator in which magnetic fields of ~2 kT are generated and measured with several diagnostics. Issues such as energy loss in solid conductors and dynamic response of current-carrying conductors to very large magnetic fields are reviewed in context with Z experiments. We describe planned flux-compression experiments that are expected to create the highest-magnitude uniform-field volumes yet attained in the laboratory.

THE NIOBIUM-THORIUM EUTECTIC ALLOY AS A HIGH-FIELD, HIGH-CURRENT SUPERCONDUCTOR

Energy Technology Data Exchange (ETDEWEB)

Cline, H. E.; Rose, R. M.; Wulff, J.

1963-03-15

Niobium-thorium eutectic alloys having fine acicuiar microstructures were produced by fast cooling frorn a vacuum melt. Although the solidified material was normal, continuity between the superconducting niobium-rich phase, which was essentially pure niobium, was attained by plastic deformation at room temperature. The resulting wire was tested for critical current at 4.2 deg K, in transverse magnetic fields up to 82.5 kilogauss; at the highest field, critical current densities of slightly more than 10/sup 4/ amps per square centimeter were observed. The critical current density was independent of applied field from 20 kilogauss to the highest field used; the level of critical current density depended on diameter in a manner that suggested dependence on cold work. It was concluded that the cold work reduced the thickness of the needles of niobium below the superconducting penetration depth, and brought them sufficiently close together to allow the superconducting correlation to interconnect the niobium, in the manner suggested by Cooper; furthermore, the constant critical current region may possibly extend to considerably higher fields. (auth)

Characterization of high-current, high-temperature superconductor current lead elements

International Nuclear Information System (INIS)

Niemann, R.C.; Evans, D.J.; Fisher, B.L.; Brockenborough, W.E.; Roberts, P.R.; Rodenbush, A.J.

1996-08-01

The refrigeration loads of current leads for superconducting magnets can be significantly reduced by using high-temperature superconductor (HTS) leads. An HTS conductor type that is well suited for this application is a laminated sintered stack of HTS powder-in-tube (PIT) tapes. The superconducting elements are normally characterized by their manufacturer by measuring critical currents at 77 K in self field. Additional characterization, which correlates electrical performance at 77 K and at lower temperatures with applied magnetic fields, provides the current lead designer and conductor element manufacturer with critical information. For HTS conductor elements comprising a laminated and sintered stack of Bi-2223 PIT tapes having an alloyed Ag sheath, this characterization uses variable applied fields and operating temperatures

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

Science.gov (United States)

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

2014-07-01

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

Measurements of fusion-protons anisotropy around the pinch axis within high-current PF-1000 experiments

Energy Technology Data Exchange (ETDEWEB)

Sadowski, M.J. [The Andrzej Soltan Institute for Nuclear Studies - IPJ, 05-400 Otwock-Swierk (Poland)] [Institute of Plasma Physics and Laser Microfusion - IPPLM, 01-497 Warsaw (Poland); Malinowska, A.; Malinowski, K.; Czaus, K.; Kwiatkowski, R.; Skladnik-Sadowska, E.; Zebrowski, J. [The Andrzej Soltan Institute for Nuclear Studies - IPJ, 05-400 Otwock-Swierk (Poland); Karpinski, L.; Paduch, M.; Scholz, M.; Stepniewski, W. [Institute of Plasma Physics and Laser Microfusion - IPPLM, 01-497 Warsaw (Poland)

2011-07-01

The paper describes measurements of fast protons produced by D-D fusion reactions during high-current discharges within the PF-1000 facility operated with the deuterium filling at 27 kV, 480 kJ. The measurements were performed by means of a set of pinhole-cameras equipped with PM-355 track detectors shielded by 80-{mu}m-thick Al-filters, which eliminated fast primary deuterons and protons of lower energy (< 3 MeV). Those cameras were placed at different angles around the pinch axis. The obtained proton images showed a distinct angular anisotropy, which was explained by an influence of local magnetic fields connected with a filamentary structure of the plasma column during the fast proton (and neutron) emission. The paper shows that in addition to measurements of a fusion neutron anisotropy it is reasonable to study also an anisotropy of fusion protons (originated from the second branch of the D-D reactions), as well as other charged fusion products. This document is composed of a paper followed by a poster

CUTLASS HF radar observations of high-latitude azimuthally propagating vortical currents in the nightside ionosphere during magnetospheric substorms

Directory of Open Access Journals (Sweden)

J. A. Wild

Full Text Available High-time resolution CUTLASS observations and ground-based magnetometers have been employed to study the occurrence of vortical flow structures propagating through the high-latitude ionosphere during magnetospheric substorms. Fast-moving flow vortices (~800 m s^-1 associated with Hall currents flowing around upward directed field-aligned currents are frequently observed propagating at high speed (~1 km s^-1 azimuthally away from the region of the ionosphere associated with the location of the substorm expansion phase onset. Furthermore, a statistical analysis drawn from over 1000 h of high-time resolution, nightside radar data has enabled the characterisation of the bulk properties of these vortical flow systems. Their occurrence with respect to substorm phase has been investigated and a possible generation mechanism has been suggested.

Key words: Ionosphere (auroral ionosphere; electric fields and currents · Magnetospheric physics (storms and substorms

Programme and current status of fast breeder reactor development in Japan

International Nuclear Information System (INIS)

Suita, T.; Oyama, A.

1977-01-01

In 1967 the Japan Atomic Energy Commission revised her long term programme after a two year study for giving principles to her nuclear energy development programme, which indicated the dominant role of nuclear energy mid 1980's in the electric power generation and stressed the necessity of developing fast breeder reactors. It also recommended to organize a nucleus to undertake this nation-wide project, bringing together the total capability available throughout the country. Accordingly, the Power Reactor and Nuclear Fuel Development Corporation (PNC) was established in 1967 to develop two sodium-cooled fast reactors, an experimental fast reactor of about 100 MW thermal and a prototype fast breeder reactor of about 300 MW electrical, both using mixed oxide fuels. Construction of the experimental fast reactor started in 1970 and was essentially completed at the end of in 1974. The precommissioning test was followed in parallel with re-evaluating quality assurance of all systems. Physics test will be initiated around the end of 1976. The conceptual design of the prototype fast breeder reactor is now toward its final stage. Surveys on its proposed site have just started. Construction will start in 1978. Beside R and D works conducted by many organizations in Japan as well as under the international cooperation, several key test facilities were installed by PNC itself to conduct in-sodium test of full-size prototype components including 50 MW steam generators and post-irradiation-examination of fuels and materials. Recently an interim report was issued to an ad-hoc committee organized by JAEC to evaluate future prospect of the fuel cycle and power reactors. This recommended start of construction of the prototype reactor as scheduled and the large demonstration reactor to be followed to the prototype. Thus the fast breeder reactor is indicated as the most indispensable in 1990's

Photo-induced current transient spectroscopy for high-resistivity neutron-transmutation-doped silicon

International Nuclear Information System (INIS)

Tokuda, Yutaka; Inoue, Yajiro; Usami, Akira

1987-01-01

Defects in high-resistivity neutron-transmutation-doped (NTD) silicon prior to annealing were studied by photo-induced current transient spectroscopy (PICTS). The thermal-neutron fluence was 9.5 x 10 17 cm -2 to give a resistivity of about 30 Ω after annealing, and the fast-neutron fluence was 9.5 x 10 16 cm -2 . Four traps with thermal emission activation energies of 0.15, 0.41. 0.47 and 0.50 eV were observed in NTD silicon. A trap with the thermal emission activation energy of 0.15 eV was considered to correspond to the divacancy. Although the clustered nature of the defects was observed, PICTS measurements suggest that the material state of high-resistivity NTD silicon is still crystalline and not amorphous. (author)

Fast IMRT with narrow high energy scanned photon beams

Energy Technology Data Exchange (ETDEWEB)

Andreassen, Bjoern; Straaring t, Sara Janek; Holmberg, Rickard; Naefstadius, Peder; Brahme, Anders [Department of Medical Radiation Physics, Karolinska Institutet and Stockholm University, P.O. Box 260, SE-171 76 Stockholm (Sweden); Department of Hospital Physics, Karolinska University Hospital, SE-171 76 Stockholm (Sweden); Department of Medical Radiation Physics, Karolinska Institutet and Stockholm University, P.O. Box 260, SE-171 76 Stockholm, Sweden and Department of Hospital Physics, Karolinska University Hospital, SE-171 76 Stockholm (Sweden)

2011-08-15

Purpose: Since the first publications on intensity modulated radiation therapy (IMRT) in the early 1980s almost all efforts have been focused on fairly time consuming dynamic or segmental multileaf collimation. With narrow fast scanned photon beams, the flexibility and accuracy in beam shaping increases, not least in combination with fast penumbra trimming multileaf collimators. Previously, experiments have been performed with full range targets, generating a broad bremsstrahlung beam, in combination with multileaf collimators or material compensators. In the present publication, the first measurements with fast narrow high energy (50 MV) scanned photon beams are presented indicating an interesting performance increase even though some of the hardware used were suboptimal. Methods: Inverse therapy planning was used to calculate optimal scanning patterns to generate dose distributions with interesting properties for fast IMRT. To fully utilize the dose distributional advantages with scanned beams, it is necessary to use narrow high energy beams from a thin bremsstrahlung target and a powerful purging magnet capable of deflecting the transmitted electron beam away from the generated photons onto a dedicated electron collector. During the present measurements the scanning system, purging magnet, and electron collimator in the treatment head of the MM50 racetrack accelerator was used with 3-6 mm thick bremsstrahlung targets of beryllium. The dose distributions were measured with diodes in water and with EDR2 film in PMMA. Monte Carlo simulations with geant4 were used to study the influence of the electrons transmitted through the target on the photon pencil beam kernel. Results: The full width at half-maximum (FWHM) of the scanned photon beam was 34 mm measured at isocenter, below 9.5 cm of water, 1 m from the 3 mm Be bremsstrahlung target. To generate a homogeneous dose distribution in a 10 x 10 cm{sup 2} field, the authors used a spot matrix of 100 equal intensity

Current and capacitance measurements as a fast diagnostic tool for evaluation of semiconductor parameters

CERN Document Server

Kemmer, J; Krause, N; Krieglmeyer, C; Yang Yi

2000-01-01

A fast qualitative method is described for evaluation of semiconductor parameters by analyzing both the capacitance/voltage (C/V) and current/voltage (I/V) characteristics of pn- or Schottky-diodes, which are fabricated on the material under investigation. The method is applied for measurement of recombination and generation lifetimes of minority charge carriers and for determination of doping profiles and distribution of active generation/recombination (G/R) centers after irradiation with Am-alpha particles and deep phosphorus implantation. Measurements on epitaxial silicon result in doping profiles and distributions of active impurities within the epi-layer.

Fast reactor fuel reprocessing in the UK

International Nuclear Information System (INIS)

Allardice, R.H.; Williams, J.; Buck, C.

1977-01-01

Enriched uranium metal fuel irradiated in the Dounreay Fast Reactor has been reprocessed and refabricated in plants specifically designed for the purpose in the U.K. since 1961. Efficient and reliable fuel recycle is essential to the development of a plutonium based fast reactor system and the importance of establishing at an early stage fast reactor fuel reprocessing has been reinforced by current world difficulties in reprocessing high burn-up thermal reactor oxide fuel. In consequence, the U.K. has decided to reprocess irradiated fuel from the 250 MW(E) Prototype Fast Reactor as an integral part of the fast reactor development programme. Flowsheet and equipment development work for the small scale fully active demonstration plant have been carried out over the past 5 years and the plant will be commissioned and ready for active operation during 1977. In parallel, a comprehensive waste management system has been developed and installed. Based on this development work and the information which will arise from active operation of the plant a parallel development programme has been initiated to provide the basis for the design of a large scale fast reactor fuel reprocessing plant to come into operation in the late 1980s to support the projected U.K. fast reactor installation programme. The paper identifies the important differences between fast reactor and thermal reactor fuel reprocessing technologies and describes some of the development work carried out in these areas for the small scale P.F.R. fuel reprocessing operation. In addition, the development programme in aid of the design of a larger scale fast reactor fuel reprocessing plant is outlined and the current design philosophy is discussed

High beam current shut-off systems in the APS linac and low energy transfer line

International Nuclear Information System (INIS)

Wang, X.; Knott, M.; Lumpkin, A.

1994-01-01

Two independent high beam current shut-off current monitoring systems (BESOCM) have been installed in the APS linac and the low energy transport line to provide personnel safety protection in the event of acceleration of excessive beam currents. Beam current is monitored by a fast current transformer (FCT) and fully redundant supervisory circuits connected to the Access Control Interlock System (ACIS) for beam intensity related shutdowns of the linac. One FCT is located at the end of the positron linac and the other in the low energy transport line, which directs beam to the positron accumulator ring (PAR). To ensure a high degree of reliability, both systems employ a continuous self-checking function, which injects a test pulse to a single-turn test winding after each ''real'' beam pulse to verify that the system is fully functional. The system is designed to be fail-safe for all possible system faults, such as loss of power, open or shorted signal or test cables, loss of external trigger, malfunction of gated integrator, etc. The system has been successfully commissioned and is now a reliable part of the total ACIS

High-sensitivity fast neutron detector KNK-2-7M

Energy Technology Data Exchange (ETDEWEB)

Koshelev, A. S., E-mail: alexsander.coshelev@yandex.ru; Dovbysh, L. Ye.; Ovchinnikov, M. A.; Pikulina, G. N.; Drozdov, Yu. M. [Russian Federal Nuclear Center All-Russian Research Institute of Experimental Physics (Russian Federation); Chuklyaev, S. V. [Research Institute of Materials Technology (Russian Federation)

2015-12-15

The construction of the fast neutron detector KNK-2-7M is briefly described. The results of the study of the detector in the pulse-counting mode are given for the fissions of {sup 237}Np nuclei in the radiator of the neutron-sensitive section and in the current mode with the separation of sectional currents of functional sections. The possibilities of determining the effective number of {sup 237}Np nuclei in the radiator of the neutronsensitive section are considered. The diagnostic possibilities of the detector in the counting mode are shown by example of the analysis of the reference data from the neutron-field characteristics in the working hall of the BR-K1 reactor. The diagnostic possibilities of the detector in the current operating mode are shown by example of the results of measuring the {sup 237}Np-fission intensity in the BR-K1 reactor power start-ups implemented in the mode of fission-pulse generation on delayed neutrons at the detector arrangement inside the reactor core cavity under conditions of a wide variation of the reactor radiation field.

A fast chopper for the Fermilab High Intensity Neutrino Source (HINS)

Energy Technology Data Exchange (ETDEWEB)

Madrak, R.; Wildman, D.; /Fermilab; Dymokde-Bradshaw, A.; Hares, J.; Kellett, P.

2008-10-01

A fast chopper capable of kicking single 2.5 MeV H-bunches spaced at 325 MHz, at rates greater than 50 MHz is needed for the Fermilab High Intensity Neutrino Source (HINS) [1]. Four 1.2 kV fast pulsers, designed and manufactured by Kentech Instruments Ltd., will drive a 0.5 m long meander made from a copper plated ceramic composite. Test results showing pulses from the first 1.2 kV pulser and meander results will be presented.

Design and Preparation of RF System for the Lower Hybrid Fast Wave Heating and Current Drive Research on VEST

Energy Technology Data Exchange (ETDEWEB)

Kim, Sun Ho; Jeong, Seung Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Hyun Woo; Lee, Byung Je [Kwang Woon University, Chuncheon (Korea, Republic of); Jo, Jong Gab; Lee, Hyun Young; Hwang, Yong Seok [Seoul National University, Seoul (Korea, Republic of)

2015-10-15

Continuous current drive is one of the key issues for tokamak to be a commercial fusion reactor. As a part of new and efficient current drive concept research by using a Lower Hybrid Fast Wave (LHFW), the experimental study is planned on Versatile Experiment Spherical Torus (VEST) and a RF system is being developed in collaboration with Kwang Woon University (KWU), Korea Accelerator Plasma Research Association (KAPRA) and Seoul National University (SNU). The LHFW RF system includes UHF band klystron, inter-digital antenna, RF diagnostics and power transmission sub components such as circulator, DC breaker, vacuum feed-thru. The design and preparation status of the RF system will be presented in the meeting in detail. A RF system has been designed and prepared for the experimental study of efficient current drive by using Lower Hybrid Fast Wave. Overall LHFW RF system including diagnostics is designed to deliver about 10 kW in UHF band. And the key hardware components including klystron and antenna are being prepared and designed through the collaboration with KWU, KAPRA and SNU.

U.S. Sodium Fast Reactor Codes and Methods: Current Capabilities and Path Forward

Energy Technology Data Exchange (ETDEWEB)

Brunett, A. J.; Fanning, T. H.

2017-06-26

The United States has extensive experience with the design, construction, and operation of sodium cooled fast reactors (SFRs) over the last six decades. Despite the closure of various facilities, the U.S. continues to dedicate research and development (R&D) efforts to the design of innovative experimental, prototype, and commercial facilities. Accordingly, in support of the rich operating history and ongoing design efforts, the U.S. has been developing and maintaining a series of tools with capabilities that envelope all facets of SFR design and safety analyses. This paper provides an overview of the current U.S. SFR analysis toolset, including codes such as SAS4A/SASSYS-1, MC2-3, SE2-ANL, PERSENT, NUBOW-3D, and LIFE-METAL, as well as the higher-fidelity tools (e.g. PROTEUS) being integrated into the toolset. Current capabilities of the codes are described and key ongoing development efforts are highlighted for some codes.

Upgrading the Fast Calorimeter Simulation in ATLAS

CERN Document Server

Schaarschmidt, Jana; The ATLAS collaboration

2017-01-01

The tremendous need for simulated samples now and even more so in the future, encourage the development of fast simulation techniques. The Fast Calorimeter Simulation is a faster though less accurate alternative to the full calorimeter simulation with Geant4. It is based on parametrizing the longitudunal and lateral energy deposits of single particles in the ATLAS calorimeter. Principal component analysis and machine learning techniques are used to improve the performance and decrease the memory need compared to the current version of the ATLAS Fast Calorimeter Simulation. The parametrizations are expanded to cover very high energies and very forward detector regions, to increase the applicability of the tool. A prototype of this upgraded Fast Calorimeter Simulation has been developed and first validations with single particles show substantial improvements over the previous version.

Generation of highly collimated high-current ion beams by skin-layer laser-plasma interaction at relativistic laser intensities

International Nuclear Information System (INIS)

Badziak, J.; Jablonski, S.; Glowacz, S.

2006-01-01

Generation of fast ion beams by laser-induced skin-layer ponderomotive acceleration has been studied using a two-dimensional (2D) two-fluid relativistic computer code. It is shown that the key parameter determining the spatial structure and angular divergence of the ion beam is the ratio d L /L n , where d L is the laser beam diameter and L n is the plasma density gradient scale length. When d L >>L n , a dense highly collimated megaampere ion (proton) beam of the ion current density approaching TA/cm 2 can be generated by skin-layer ponderomotive acceleration, even with a tabletop subpicosecond laser

Opportunities for Integrated Fast Ignition program

International Nuclear Information System (INIS)

Mackinnon, A. J.; Key, M. H.; Hatchett, S. P.; Tabak, M.; Town, R.; Gregori, G.; Patel, P. K.; Snavely, R.; Freeman, R. R.; Stephens, R. B.; Beg, F.

2005-01-01

Experiments designed to investigate the physics of particle transport and heating of dense plasmas have been carried out in an number of facilities around the world since the publication of the fast ignition concept in 1997. To date a number of integrated experiments, examining the capsule implosion and subsequent heating have been carried out on the Gekko facility at the Institute of Laser Engineering (ILE) Osaka, Japan. The coupling of energy by the short pulse into the pre-compressed core in these experiments was very encouraging. More facilities capable of carrying out integrated experiments are currently under construction: Firex at ILEm the Omega EP facility at the University of Rochester, Z PW at Sandia National Lab, LIL in France and eventually high energy PW beams on the NIF. This presentation will review the current status of experiments in this area and discuss the capabilities of integrated fast ignition research that will be required to design the proof of principle and scaling experiments for fast ignition to be carried on the NIF. (Author)

Technical Meeting on Impact of Fukushima Event on Current and Future Fast Reactor Designs. Working Material

International Nuclear Information System (INIS)

2012-01-01

The overall purpose of the Technical Meeting was to recognize and analyse the implications of the accident occurred at the Fukushima Dai-ichi Nuclear Power Station on current and future fast neutron systems design and operation. The aim was to provide a global forum for discussing the principal lessons learned from this event, and thus to review safety principles and characteristics of existing and future fast neutron concepts, especially in relation with extreme natural events which potentially may lead to severe accident scenarios. The participants also presented and discussed innovative technical solutions, design features and countermeasures for design extension conditions - including earthquakes, tsunami and other extreme natural hazards - which can enhance the safety level of existing and future fast neutron systems. Furthermore, the meeting gave the opportunity to present advanced methods for the evaluation of the robustness of plants against design extension conditions. Another important goal of this TM was to discuss how to harmonize safety approaches and goals for next generation’s fast reactors. Finally, the meeting was intended to identify areas where further research and development in nuclear safety, technology and engineering in the light of the Fukushima accident are needed. In the frame of the implementation of its Nuclear Safety Action Plan endorsed by all Member States, the IAEA will consider these areas as potential technical topics for new Coordinated Research Projects, to be launched in the near future

Can nanofluidic chemical release enable fast, high resolution neurotransmitter-based neurostimulation?

Directory of Open Access Journals (Sweden)

Peter D Jones

2016-03-01

Full Text Available Artificial chemical stimulation could provide improvements over electrical neurostimulation. Physiological neurotransmission between neurons relies on the nanoscale release and propagation of specific chemical signals to spatially-localized receptors. Current knowledge of nanoscale fluid dynamics and nanofluidic technology allows us to envision artificial mechanisms to achieve fast, high resolution neurotransmitter release. Substantial technological development is required to reach this goal. Nanofluidic technology — rather than microfluidic — will be necessary; this should come as no surprise given the nanofluidic nature of neurotransmission.This perspective reviews the state of the art of high resolution electrical neuroprostheses and their anticipated limitations. Chemical release rates from nanopores are compared to rates achieved at synapses and with iontophoresis. A review of microfluidic technology justifies the analysis that microfluidic control of chemical release would be insufficient. Novel nanofluidic mechanisms are discussed, and we propose that hydrophobic gating may allow control of chemical release suitable for mimicking neurotransmission. The limited understanding of hydrophobic gating in artificial nanopores and the challenges of fabrication and large-scale integration of nanofluidic components are emphasized. Development of suitable nanofluidic technology will require dedicated, long-term efforts over many years.

The Fast Tracker Real Time Processor: high quality real-time tracking at ATLAS

CERN Document Server

Stabile, A; The ATLAS collaboration

2011-01-01

As the LHC luminosity is ramped up to the design level of 1x1034 cm−2 s−1 and beyond, the high rates, multiplicities, and energies of particles seen by the detectors will pose a unique challenge. Only a tiny fraction of the produced collisions can be stored on tape and immense real-time data reduction is needed. An effective trigger system must maintain high trigger efficiencies for the most important physics and at the same time suppress the enormous QCD backgrounds. This requires massive computing power to minimize the online execution time of complex algorithms. A multi-level trigger is an effective solution for an otherwise impossible problem. The Fast Tracker (FTK)[1], [2] is a proposed upgrade to the current ATLAS trigger system that will operate at full Level-1 output rates and provide high quality tracks reconstructed over the entire detector by the start of processing in Level-2. FTK is a dedicated Super Computer based on a mixture of advanced technologies. The architecture broadly employs powerf...

Hyperuricemia Is a Risk Factor for the Onset of Impaired Fasting Glucose in Men with a High Plasma Glucose Level: A Community-Based Study

Science.gov (United States)

Miyake, Teruki; Kumagi, Teru; Furukawa, Shinya; Hirooka, Masashi; Kawasaki, Keitarou; Koizumi, Mitsuhito; Todo, Yasuhiko; Yamamoto, Shin; Abe, Masanori; Kitai, Kohichiro; Matsuura, Bunzo; Hiasa, Yoichi

2014-01-01

Background It is not clear whether elevated uric acid is a risk factor for the onset of impaired fasting glucose after stratifying by baseline fasting plasma glucose levels. We conducted a community-based retrospective longitudinal cohort study to clarify the relationship between uric acid levels and the onset of impaired fasting glucose, according to baseline fasting plasma glucose levels. Methods We enrolled 6,403 persons (3,194 men and 3,209 women), each of whom was 18–80 years old and had >2 annual check-ups during 2003–2010. After excluding persons who had fasting plasma glucose levels ≥6.11 mM and/or were currently taking anti-diabetic agents, the remaining 5,924 subjects were classified into quartiles according to baseline fasting plasma glucose levels. The onset of impaired fasting glucose was defined as fasting plasma glucose ≥6.11 mM during the observation period. Results In the quartile groups, 0.9%, 2.1%, 3.4%, and 20.2% of the men developed impaired fasting glucose, respectively, and 0.1%, 0.3%, 0.5%, and 5.6% of the women developed impaired fasting glucose, respectively (P trend fasting glucose in men with highest-quartile fasting plasma glucose levels (adjusted hazard ratio, 1.003; 95% confidence interval, 1.0001–1.005, P = 0.041). Conclusions Among men with high fasting plasma glucose, hyperuricemia may be independently associated with an elevated risk of developing impaired fasting glucose. PMID:25237894

The Booster to AGS beam transfer fast kicker systems

International Nuclear Information System (INIS)

Zhang, W.; Bunicci, J.; Soukas, A.V.; Zhang, S.Y.

1992-01-01

The Brookhaven AGS Booster has a very successful commissioning period in June 1991. The third phase of that commissioning was a beam extraction test. The Booster extraction fast kicker (F3) deflected a 1.2 GeV proton beam from the Booster circulating orbit into the extraction septum aperture, partially down the extraction line to a temporary beam stop. Now, the Booster is committed to the AGS operations program for both heavy ion and proton beams. Thus, the Booster extraction and the corresponding AGS injection systems must operate routinely up to a pulse repetition frequency of 7.5 Hertz, and up to a beam energy of 1.5 Gev. The injection fast kicker is located in the A5 section of the AGS ring and is used to deflect the proton or heavy ion beam into its final AGS closed orbit. A distinctive feature of the AGS injection fast kicker modulators is the tail-bitting function required for proton beam injection. This enables the system to produce a fast current fall time to go along with the high current pulse amplitude with a fast rise time. The AGS injection fast kicker system has three pulse modulators, and each modulator consists of two thyratrons. The main PFN thyratrons switch on the current, and the tail bitting thyratrons are used to force the magnet current to decrease rapidly. Two digital pulse delay generators are used to align the main thyratrons and the tail bitting thyratrons respectively. The system has been tested and installed. The final commissioning of the Booster to AGS beam transfer line and injection is currently being undertaken. In this article, the system design, realization techniques and performance data will be presented

MgB2-based superconductors for fault current limiters

Science.gov (United States)

Sokolovsky, V.; Prikhna, T.; Meerovich, V.; Eisterer, M.; Goldacker, W.; Kozyrev, A.; Weber, H. W.; Shapovalov, A.; Sverdun, V.; Moshchil, V.

2017-02-01

A promising solution of the fault current problem in power systems is the application of fast-operating nonlinear superconducting fault current limiters (SFCLs) with the capability of rapidly increasing their impedance, and thus limiting high fault currents. We report the results of experiments with models of inductive (transformer type) SFCLs based on the ring-shaped bulk MgB2 prepared under high quasihydrostatic pressure (2 GPa) and by hot pressing technique (30 MPa). It was shown that the SFCLs meet the main requirements to fault current limiters: they possess low impedance in the nominal regime of the protected circuit and can fast increase their impedance limiting both the transient and the steady-state fault currents. The study of quenching currents of MgB2 rings (SFCL activation current) and AC losses in the rings shows that the quenching current density and critical current density determined from AC losses can be 10-20 times less than the critical current determined from the magnetization experiments.

System for evaluating weld quality using eddy currents

Science.gov (United States)

Todorov, Evgueni I.; Hay, Jacob

2017-12-12

Electromagnetic and eddy current techniques for fast automated real-time and near real-time inspection and monitoring systems for high production rate joining processes. An eddy current system, array and method for the fast examination of welds to detect anomalies such as missed seam (MS) and lack of penetration (LOP) the system, array and methods capable of detecting and sizing surface and slightly subsurface flaws at various orientations in connection with at least the first and second weld pass.

The effect of the fast neutron current on the amino acid contents and nucleic acid synthesis in maize plants

International Nuclear Information System (INIS)

Akhundova, N.I.

2001-01-01

At the present time the effects of external influences on the genetic structures of the plant cells and the transmission of the accepted signals to other cellular structures and then to the whole organism have actively been studied. According to the opinion of a number of authors the gene expression and repression are immediate responses to the environment changes. To affect the plant genetic apparatus it is quite enough to expose it to some factors such as gamma rays, X- rays, neutron currents, saline-, temperature- or osmotic stresses. At the current stage of the research of the molecular mechanisms of the plant adaptation to the environment changes the priority goal is to ascertain the nature of the influence of the above mentioned factors on the processes of DNA replication and transcription, as the nucleic acids are the targets for external effects. The fast neutron current is one of the factors that influence the plant growth and development. Unlike gamma rays, the mechanism of the neutron irradiation on the plant genetic apparatus is very poorly studied. The objective of our research was the study of the fast neutron current effects on the DNA replication and transcription processes and amino acid synthesis in the irradiated maize plants

Noninductive current drive for INTOR: A comparison of four driver options

International Nuclear Information System (INIS)

Ehst, D.A.; Evans, K. Jr.; Mikkelsen, D.R.; Ignat, D.W.; Mau, T.K.

1987-01-01

The current drive power and normalized efficiency are calculated for the INTOR tokamak, including spatial profiles of the plasma and current density. Current drive requirements are computed for purely steady state operation with no electromotive force and also in the presence of a reversed emf typical of start-up or transformer recharging. Results are obtained for lower-hybrid-waves, high frequency fast waves, low frequency fast waves and neutral beam injection

Accelerated Irradiations for High Dose Microstructures in Fast Reactor Alloys

Energy Technology Data Exchange (ETDEWEB)

Jiao, Zhijie [Univ. of Michigan, Ann Arbor, MI (United States)

2017-03-31

The objective of this project is to determine the extent to which high dose rate, self-ion irradiation can be used as an accelerated irradiation tool to understand microstructure evolution at high doses and temperatures relevant to advanced fast reactors. We will accomplish the goal by evaluating phase stability and swelling of F-M alloys relevant to SFR systems at very high dose by combining experiment and modeling in an effort to obtain a quantitative description of the processes at high and low damage rates.

High-efficiency toroidal current drive using low-phase-velocity kinetic Alfven waves

International Nuclear Information System (INIS)

Puri, S.

1991-09-01

A method for obtaining efficient current drive in Tokamaks using low-phase-velocity (v ρ = ω/K parallel ∝ 0.1v te ) kinetic Alfen wave is proposed. The wave momentum, imparted primarily to the trapped electrons by Landau damping, is stored as the canonical angular momentum via the Ware pinch. In steady state, collisions restore the pinched electrons to their original phase-space configuration, in the process releasing the stored canonical angular momentum to the background ions and electrons in proportion to the respective collision frequencies. Despite the loss of a part of the original impulse to the plasma ions, well over half the wave momentum is ultimately delivered to the bulk-plasma electrons, resulting in an efficient current drive. A normalized current-drive efficiency γ = R 0 20 > I/P ∝ 2 would be feasible using the subthermal kinetic-Alfen-wave current drive in a Tokamak of reactor parameters. Optimum antenna loading conditions are described. The problem of accessibility is discussed. In an elongated, high-β plasma with a density dependence n e ∝ (1-ρ 2 ) Χn , accessibility is restricted to ρ > or approx. 3/(4A Χn ), where A is the aspect ratio. For current drive at still lower values of ρ, operation in conjunction with fast-wave current drive is suggested. (orig.)

Measurement of fast risetime megampere currents by quartz gauge

International Nuclear Information System (INIS)

Williams, R.R.; McDaniel, D.H.; Stinnett, R.W.

1980-01-01

Quartz gauges have been used on the Sandia National Laboratories Proto II accelerator to measure current in the magnetically insulated transmission line at the 11 TW power level. The accelerator delivers 3.5 MA at 2 x 10 14 A/s in a 40 ns pulse to a 0.0127 m diameter aluminum liner to produce a high density plasma. At this radius and dI/dt levels, the B-dot monitors no longer function for the measurement of load current because the monitor suffers electrical breakdown. Quartz pressure gauges mounted at a radius of 0.0086 m have successfully measured the magnetic pressure due to the load current with nanosecond temporal resolution

High current density ion source

International Nuclear Information System (INIS)

King, H.J.

1977-01-01

A high-current-density ion source with high total current is achieved by individually directing the beamlets from an electron bombardment ion source through screen and accelerator electrodes. The openings in these screen and accelerator electrodes are oriented and positioned to direct the individual beamlets substantially toward a focus point. 3 figures, 1 table

High flux-fluence measurements in fast reactors

International Nuclear Information System (INIS)

Lippincott, E.P.; Ulseth, J.A.

1977-01-01

Characterization of irradiation environments for fuels and materials tests in fast reactors requires determination of the neutron flux integrated over times as long as several years. An accurate integration requires, therefore, passive dosimetry monitors with long half-life or stable products which can be conveniently measured. In addition, burn-up, burn-in, and burn-out effects must be considered in high flux situations and use of minimum quantities of dosimeter materials is often desirable. These conditions force the use of dosimeter and dosimeter container designs, measured products, and techniques that are different from those that are used in critical facilities and other well-characterized benchmark fields. Recent measurements in EBR-II indicate that high-accuracy results can be attained and that tie-backs to benchmark field technique calibrations can be accomplished

Fast wire scanner for intense electron beams

Directory of Open Access Journals (Sweden)

T. Moore

2014-02-01

Full Text Available We have developed a cost-effective, fast rotating wire scanner for use in accelerators where high beam currents would otherwise melt even carbon wires. This new design uses a simple planetary gear setup to rotate a carbon wire, fixed at one end, through the beam at speeds in excess of 20  m/s. We present results from bench tests, as well as transverse beam profile measurements taken at Cornell’s high-brightness energy recovery linac photoinjector, for beam currents up to 35 mA.

High-performance rechargeable batteries with fast solid-state ion conductors

Energy Technology Data Exchange (ETDEWEB)

Farmer, Joseph C.

2017-06-27

A high-performance rechargeable battery using ultra-fast ion conductors. In one embodiment the rechargeable battery apparatus includes an enclosure, a first electrode operatively connected to the enclosure, a second electrode operatively connected to the enclosure, a nanomaterial in the enclosure, and a heat transfer unit.

HbA1c, fasting and 2 h plasma glucose in current, ex- and never-smokers

DEFF Research Database (Denmark)

Soulimane, Soraya; Simon, Dominique; Herman, William H

2014-01-01

AIMS/HYPOTHESIS: The relationships between smoking and glycaemic variables have not been well explored. We compared HbA1c, fasting plasma glucose (FPG) and 2 h plasma glucose (2H-PG) in current, ex- and never-smokers. METHODS: This meta-analysis used individual data from 16,886 men and 18,539 women......, there was no significant difference between current and never-smokers (-0.004 mmol/l [-0.03, 0.02]) but FPG was higher in ex-smokers (0.12 mmol/l [0.09, 0.14]). In comparison with never-smokers, 2H-PG was lower (-0.44 mmol/l [-0.52, -0.37]) in current smokers, with no difference for ex-smokers (0.02 mmol/l [-0.06, 0...... as screened by 2H-PG, in comparison with never-smokers. CONCLUSION/INTERPRETATION: Across this heterogeneous group of studies, current smokers had a higher HbA1c and lower 2H-PG than never-smokers. This will affect the chances of smokers being diagnosed with diabetes....

Fast-reactor fuel reprocessing in the United Kingdom

International Nuclear Information System (INIS)

Allardice, R.H.; Buck, C.; Williams, J.

1977-01-01

Enriched uranium metal fuel irradiated in the Dounreay Fast Reactor has been reprocessed and refabricated in plants specifically designed for the purpose in the United Kingdom since 1961. Efficient and reliable fuel recycle is essential to the development of a plutonium-based fast-reactor system, and the importance of establishing at an early stage fast-reactor fuel reprocessing has been reinforced by current world difficulties in reprocessing high-burnup thermal-reactor oxide fuel. The United Kingdom therefore decided to reprocess irradiated fuel from the 250MW(e) Prototype Fast Reactor (PFR) as an integral part of the fast reactor development programme. Flowsheet and equipment development work for the small-scale fully active demonstration plant has been carried out since 1972, and the plant will be commissioned and ready for active operation during 1977. In parallel, a comprehensive waste-management system has been developed and installed. Based on this development work and the information which will arise from active operation of the plant, a parallel development programme has been initiated to provide the basis for the design of a large-scale fast-reactor fuel-reprocessing plant to come into operation in the late 1980s to support the projected UK fast-reactor installation programme. The paper identifies the important differences between fast-reactor and thermal-reactor fuel-reprocessing technologies and describes some of the development work carried out in these areas for the small-scale PFR fuel-reprocessing operation. In addition, the development programme in aid of the design of a larger scale fast-reactor fuel-reprocessing plant is outlined and the current design philosophy discussed. (author)

High-intensity interval exercise attenuates but does not eliminate endothelial dysfunction after a fast food meal.

Science.gov (United States)

Tucker, Wesley J; Sawyer, Brandon J; Jarrett, Catherine L; Bhammar, Dharini M; Ryder, Justin R; Angadi, Siddhartha S; Gaesser, Glenn A

2018-02-01

We investigated whether two different bouts of high-intensity interval exercise (HIIE) could attenuate postprandial endothelial dysfunction. Thirteen young (27 ± 1 yr), nonexercise-trained men underwent three randomized conditions: 1) four 4-min intervals at 85-95% of maximum heart rate separated by 3 min of active recovery (HIIE 4 × 4), 2) 16 1-min intervals at 85-95% of maximum heart rate separated by 1 min of active recovery (HIIE 16 × 1), and 3) sedentary control. HIIE was performed in the afternoon, ~18 h before the morning fast food meal (1,250 kcal, 63g of fat). Brachial artery flow-mediated dilation (FMD) was performed before HIIE ( baseline 1), during fasting before meal ingestion ( baseline 2), and 30 min, 2 h, and 4 h postprandial. Capillary glucose and triglycerides were assessed at fasting, 30 min, 1 h, 2 h, and 4 h (triglycerides only). Both HIIE protocols increased fasting FMD compared with control (HIIE 4 × 4: 6.1 ± 0.4%, HIIE 16 × 1: 6.3 ± 0.5%, and control: 5.1 ± 0.4%, P fast food meal can attenuate but not entirely eliminate postprandial decreases in FMD. This effect is not dependent on reductions in postprandial lipemia or glycemia. NEW & NOTEWORTHY Two similar high-intensity interval exercise (HIIE) protocols performed ∼18 h before ingestion of a high-energy fast food meal attenuated but did not entirely eliminate postprandial endothelial dysfunction in young men largely by improving fasting endothelial function. Both HIIE protocols produced essentially identical results, suggesting high reproducibility of HIIE effects.

Numerical study of the electron heating and current drive by the fast waves in the JFT-2M tokamak plasma

International Nuclear Information System (INIS)

Yamamoto, Takumi; Uesugi, Yoshihiko; Hoshino, Katsumichi; Kawashima, Hisato; Ohtsuka, Hideo

1986-08-01

A 200 MHz fast wave experiment for the JET-2M tokamak is examined. Noticeable single-path electron Landau damping of the fast waves with the parallel refractive index of N // = 4 is expected in the plasma with electron temperature more than 2.5 keV at the electron density of n e = 1.5 x 10 19 m -3 . Furthermore, it is shown that 8 kA of the plasma current is driven by the fast waves with N //≅ 2 at n e = 3 x 10 19 m -3 in the single-path damping when 100 kW of the rf power radiates into the plasma in the presence of the hot electrons with the temperature of 19 keV and the fraction of the density of 2 %. (author)

An option for the Brazilian nuclear project: necessity of fast breeder reactors and core design for an experimental fast reactor

International Nuclear Information System (INIS)

Ishiguro, Y.

1983-01-01

In order to assure the continued utilization of fission energy, development of fast breeder reactors (FBRs) is a necessity. Binary fueled LMFBRs are proposed as the best type for future Brazilian nuclear systems. The inherent safety characteristics are superior to current FBRs and an efficient utilization of the abundant thorium is possible. A first step and a basic tool for the development of FBR technologies is the construction and operation of an experimental fast reactor (EFR). A series of core designs for a 90 MW EFR is studied and possible options and the magnitudes of principal parameters are identified. Flexible modifications of the core and sufficiently high fast fluxes for fuel and materials irradiations appear possible. (Author) [pt

A fast mass spring model solver for high-resolution elastic objects

Science.gov (United States)

Zheng, Mianlun; Yuan, Zhiyong; Zhu, Weixu; Zhang, Guian

2017-03-01

Real-time simulation of elastic objects is of great importance for computer graphics and virtual reality applications. The fast mass spring model solver can achieve visually realistic simulation in an efficient way. Unfortunately, this method suffers from resolution limitations and lack of mechanical realism for a surface geometry model, which greatly restricts its application. To tackle these problems, in this paper we propose a fast mass spring model solver for high-resolution elastic objects. First, we project the complex surface geometry model into a set of uniform grid cells as cages through *cages mean value coordinate method to reflect its internal structure and mechanics properties. Then, we replace the original Cholesky decomposition method in the fast mass spring model solver with a conjugate gradient method, which can make the fast mass spring model solver more efficient for detailed surface geometry models. Finally, we propose a graphics processing unit accelerated parallel algorithm for the conjugate gradient method. Experimental results show that our method can realize efficient deformation simulation of 3D elastic objects with visual reality and physical fidelity, which has a great potential for applications in computer animation.

Complexity reduction in the H.264/AVC using highly adaptive fast mode decision based on macroblock motion activity

Science.gov (United States)

Abdellah, Skoudarli; Mokhtar, Nibouche; Amina, Serir

2015-11-01

The H.264/AVC video coding standard is used in a wide range of applications from video conferencing to high-definition television according to its high compression efficiency. This efficiency is mainly acquired from the newly allowed prediction schemes including variable block modes. However, these schemes require a high complexity to select the optimal mode. Consequently, complexity reduction in the H.264/AVC encoder has recently become a very challenging task in the video compression domain, especially when implementing the encoder in real-time applications. Fast mode decision algorithms play an important role in reducing the overall complexity of the encoder. In this paper, we propose an adaptive fast intermode algorithm based on motion activity, temporal stationarity, and spatial homogeneity. This algorithm predicts the motion activity of the current macroblock from its neighboring blocks and identifies temporal stationary regions and spatially homogeneous regions using adaptive threshold values based on content video features. Extensive experimental work has been done in high profile, and results show that the proposed source-coding algorithm effectively reduces the computational complexity by 53.18% on average compared with the reference software encoder, while maintaining the high-coding efficiency of H.264/AVC by incurring only 0.097 dB in total peak signal-to-noise ratio and 0.228% increment on the total bit rate.

Characterisation Of The Beam Plasma In High Current, Low Energy Ion Beams For Implanters

International Nuclear Information System (INIS)

Fiala, J.; Armour, D. G.; Berg, J. A. van der; Holmes, A. J. T.; Goldberg, R. D.; Collart, E. H. J.

2006-01-01

The effective transport of high current, positive ion beams at low energies in ion implanters requires the a high level of space charge compensation. The self-induced or forced introduction of electrons is known to result in the creation of a so-called beam plasma through which the beam propagates. Despite the ability of beams at energies above about 3-5 keV to create their own neutralising plasmas and the development of highly effective, plasma based neutralising systems for low energy beams, very little is known about the nature of beam plasmas and how their characteristics and capabilities depend on beam current, beam energy and beamline pressure. These issues have been addressed in a detailed scanning Langmuir probe study of the plasmas created in beams passing through the post-analysis section of a commercial, high current ion implanter. Combined with Faraday cup measurements of the rate of loss of beam current in the same region due to charge exchange and scattering collisions, the probe data have provided a valuable insight into the nature of the slow ion and electron production and loss processes. Two distinct electron energy distribution functions are observed with electron temperatures ≥ 25 V and around 1 eV. The fast electrons observed must be produced in their energetic state. By studying the properties of the beam plasma as a function of the beam and beamline parameters, information on the ways in which the plasma and the beam interact to reduce beam blow-up and retain a stable plasma has been obtained

A Lean, Fast Mars Round-trip Mission Architecture: Using Current Technologies for a Human Mission in the 2030s

Science.gov (United States)

Bailey, Lora; Folta, David; Barbee, Brent W.; Vaughn, Frank; Kirchman, Frank; Englander, Jacob; Campbell, Bruce; Thronson, Harley; Lin, Tzu Yu

2013-01-01

We present a lean fast-transfer architecture concept for a first human mission to Mars that utilizes current technologies and two pivotal parameters: an end-to-end Mars mission duration of approximately one year, and a deep space habitat of approximately 50 metric tons. These parameters were formulated by a 2012 deep space habitat study conducted at the NASA Johnson Space Center (JSC) that focused on a subset of recognized high- engineering-risk factors that may otherwise limit space travel to destinations such as Mars or near-Earth asteroid (NEA)s. With these constraints, we model and promote Mars mission opportunities in the 2030s enabled by a combination of on-orbit staging, mission element pre-positioning, and unique round-trip trajectories identified by state-of-the-art astrodynamics algorithms.

THE ROLE OF FAST MAGNETOSONIC WAVES IN THE RELEASE AND CONVERSION VIA RECONNECTION OF ENERGY STORED BY A CURRENT SHEET

Energy Technology Data Exchange (ETDEWEB)

Longcope, D. W.; Tarr, L. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States)

2012-09-10

Using a simple two-dimensional, zero-{beta} model, we explore the manner by which reconnection at a current sheet releases and dissipates free magnetic energy. We find that only a small fraction (3%-11% depending on current-sheet size) of the energy is stored close enough to the current sheet to be dissipated abruptly by the reconnection process. The remaining energy, stored in the larger-scale field, is converted to kinetic energy in a fast magnetosonic disturbance propagating away from the reconnection site, carrying the initial current and generating reconnection-associated flows (inflow and outflow). Some of this reflects from the lower boundary (the photosphere) and refracts back to the X-point reconnection site. Most of this inward wave energy is reflected back again and continues to bounce between X-point and photosphere until it is gradually dissipated, over many transits. This phase of the energy dissipation process is thus global and lasts far longer than the initial purely local phase. In the process, a significant fraction of the energy (25%-60%) remains as undissipated fast magnetosonic waves propagating away from the reconnection site, primarily upward. This flare-generated wave is initiated by unbalanced Lorentz forces in the reconnection-disrupted current sheet, rather than by dissipation-generated pressure, as some previous models have assumed. Depending on the orientation of the initial current sheet, the wave front is either a rarefaction, with backward-directed flow, or a compression, with forward-directed flow.

Performance of Fast AMC in E-UTRAN Uplink

DEFF Research Database (Denmark)

Rosa, Claudio; López Villa, Dimas; Úbeda Castellanos, Carlos

2008-01-01

Evolved (E-) UTRA is currently being standardized as a long term evolution (LTE) of the 3GPP radio access technology. One of the goals of E-UTRA is to achieve 2-4 times the spectral efficiency and user throughputs compared to HSUPA/HSDPA [1]. Support for fast link adaptation based on adaptive...... and interference conditions. It is shown that despite measurement errors and the high variability of uplink inter-cell interference, fast AMC can boost the capacity of E-UTRA uplink by approximately 20% to 25%....

Heating and current drive on NSTX

Science.gov (United States)

Wilson, J. R.; Batchelor, D.; Carter, M.; Hosea, J.; Ignat, D.; LeBlanc, B.; Majeski, R.; Ono, M.; Phillips, C. K.; Rogers, J. H.; Schilling, G.

1997-04-01

Low aspect ratio tokamaks pose interesting new challenges for heating and current drive. The NSTX (National Spherical Tokamak Experiment) device to be built at Princeton is a low aspect ratio toroidal device that has the achievement of high toroidal beta (˜45%) and non-inductive operation as two of its main research goals. To achieve these goals significant auxiliary heating and current drive systems are required. Present plans include ECH (Electron cyclotron heating) for pre-ionization and start-up assist, HHFW (high harmonic fast wave) for heating and current drive and eventually NBI (neutral beam injection) for heating, current drive and plasma rotation.

Scanning fast and slow: current limitations of 3 Tesla functional MRI and future potential

Science.gov (United States)

Boubela, Roland N.; Kalcher, Klaudius; Nasel, Christian; Moser, Ewald

2014-02-01

Functional MRI at 3T has become a workhorse for the neurosciences, e.g., neurology, psychology, and psychiatry, enabling non-invasive investigation of brain function and connectivity. However, BOLD-based fMRI is a rather indirect measure of brain function, confounded by fluctuation related signals, e.g. head or brain motion, brain pulsation, blood flow, intermixed with susceptibility differences close or distant to the region of neuronal activity. Even though a plethora of preprocessing strategies have been published to address these confounds, their efficiency is still under discussion. In particular, physiological signal fluctuations closely related to brain supply may mask BOLD signal changes related to "true" neuronal activation. Here we explore recent technical and methodological advancements aimed at disentangling the various components, employing fast multiband vs. standard EPI, in combination with fast temporal ICA.Our preliminary results indicate that fast (TRstudied and task performance better correlated to other measures. This should increase specificity and reliability in fMRI studies. Furthermore, physiological signal changes during scanning may then be recognized as a source of information rather than a nuisance. As we are currently still undersampling the complexity of the brain, even at a rather coarse macroscopic level, we should be very cautious in the interpretation of neuroscientific findings, in particular when comparing different groups (e.g., age, sex, medication, pathology, etc.). From a technical point of view our goal should be to sample brain activity at layer specific resolution with low TR, covering as much of the brain as possible without violating SAR limits. We hope to stimulate discussion towards a better understanding and a more quantitative use of fMRI.

Improving sensitivity of residual current transformers to high frequency earth fault currents

Directory of Open Access Journals (Sweden)

Czapp Stanislaw

2017-09-01

Full Text Available For protection against electric shock in low voltage systems residual current devices are commonly used. However, their proper operation can be interfered when high frequency earth fault current occurs. Serious hazard of electrocution exists then. In order to detect such a current, it is necessary to modify parameters of residual current devices, especially the operating point of their current transformer. The authors proposed the modification in the structure of residual current devices. This modification improves sensitivity of residual current devices when high frequency earth fault current occurs. The test of the modified residual current device proved that the authors’ proposition is appropriate.

High temperature superconductor current leads

International Nuclear Information System (INIS)

Zeimetz, B.; Liu, H.K.; Dou, S.X.

1996-01-01

Full text: The use of superconductors in high electrical current applications (magnets, transformers, generators etc.) usually requires cooling with liquid Helium, which is very expensive. The superconductor itself produces no heat, and the design of Helium dewars is very advanced. Therefore most of the heat loss, i.e. Helium consumption, comes from the current lead which connects the superconductor with its power source at room temperature. The current lead usually consists of a pair of thick copper wires. The discovery of the High Temperature Superconductors makes it possible to replace a part of the copper with superconducting material. This drastically reduces the heat losses because a) the superconductor generates no resistive heat and b) it is a very poor thermal conductor compared with the copper. In this work silver-sheathed superconducting tapes are used as current lead components. The work comprises both the production of the tapes and the overall design of the leads, in order to a) maximize the current capacity ('critical current') of the superconductor, b) minimize the thermal conductivity of the silver clad, and c) optimize the cooling conditions

Reducing AC-Winding Losses in High-Current High-Power Inductors

DEFF Research Database (Denmark)

Nymand, Morten; Madawala, Udaya K.; Andersen, Michael Andreas E.

2009-01-01

Foil windings are preferable in high-current high-power inductors to realize compact designs and to reduce dc-current losses. At high frequency, however, proximity effect will cause very significant increase in ac resistance in multi-layer windings, and lead to high ac winding losses. This paper ...

High current induction linacs

International Nuclear Information System (INIS)

Barletta, W.; Faltens, A.; Henestroza, E.; Lee, E.

1994-07-01

Induction linacs are among the most powerful accelerators in existence. They have accelerated electron bunches of several kiloamperes, and are being investigated as drivers for heavy ion driven inertial confinement fusion (HIF), which requires peak beam currents of kiloamperes and average beam powers of some tens of megawatts. The requirement for waste transmutation with an 800 MeV proton or deuteron beam with an average current of 50 mA and an average power of 40 MW lies midway between the electron machines and the heavy ion machines in overall difficulty. Much of the technology and understanding of beam physics carries over from the previous machines to the new requirements. The induction linac allows use of a very large beam aperture, which may turn out to be crucial to reducing beam loss and machine activation from the beam halo. The major issues addressed here are transport of high intensity beams, availability of sources, efficiency of acceleration, and the state of the needed technology for the waste treatment application. Because of the transformer-like action of an induction core and the accompanying magnetizing current, induction linacs make the most economic sense and have the highest efficiencies with large beam currents. Based on present understanding of beam transport limits, induction core magnetizing current requirements, and pulse modulators, the efficiencies could be very high. The study of beam transport at high intensities has been the major activity of the HIF community. Beam transport and sources are limiting at low energies but are not significant constraints at the higher energies. As will be shown, the proton beams will be space-charge-dominated, for which the emittance has only a minor effect on the overall beam diameter but does determine the density falloff at the beam edge

Nodal method for fast reactor analysis

International Nuclear Information System (INIS)

Shober, R.A.

1979-01-01

In this paper, a nodal method applicable to fast reactor diffusion theory analysis has been developed. This method has been shown to be accurate and efficient in comparison to highly optimized finite difference techniques. The use of an analytic solution to the diffusion equation as a means of determining accurate coupling relationships between nodes has been shown to be highly accurate and efficient in specific two-group applications, as well as in the current multigroup method

The new ATLAS Fast Calorimeter Simulation

CERN Document Server

AUTHOR|(INSPIRE)INSPIRE-00223142; The ATLAS collaboration

2017-01-01

Current and future need for large scale simulated samples motivate the development of reliable fast simulation techniques. The new Fast Calorimeter Simulation is an improved parameterized response of single particles in the ATLAS calorimeter that aims to accurately emulate the key features of the detailed calorimeter response as simulated with Geant4, yet approximately ten times faster. Principal component analysis and machine learning techniques are used to improve the performance and decrease the memory need compared to the current version of the ATLAS Fast Calorimeter Simulation. A prototype of this new Fast Calorimeter Simulation is in development and its integration into the ATLAS simulation infrastructure is ongoing.

The new ATLAS Fast Calorimeter Simulation

Science.gov (United States)

Schaarschmidt, J.; ATLAS Collaboration

2017-10-01

Current and future need for large scale simulated samples motivate the development of reliable fast simulation techniques. The new Fast Calorimeter Simulation is an improved parameterized response of single particles in the ATLAS calorimeter that aims to accurately emulate the key features of the detailed calorimeter response as simulated with Geant4, yet approximately ten times faster. Principal component analysis and machine learning techniques are used to improve the performance and decrease the memory need compared to the current version of the ATLAS Fast Calorimeter Simulation. A prototype of this new Fast Calorimeter Simulation is in development and its integration into the ATLAS simulation infrastructure is ongoing.

BRAIN initiative: fast and parallel solver for real-time monitoring of the eddy current in the brain for TMS applications.

Science.gov (United States)

Sabouni, Abas; Pouliot, Philippe; Shmuel, Amir; Lesage, Frederic

2014-01-01

This paper introduce a fast and efficient solver for simulating the induced (eddy) current distribution in the brain during transcranial magnetic stimulation procedure. This solver has been integrated with MRI and neuronavigation software to accurately model the electromagnetic field and show eddy current in the head almost in real-time. To examine the performance of the proposed technique, we used a 3D anatomically accurate MRI model of the 25 year old female subject.

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

Energy Technology Data Exchange (ETDEWEB)

Chacon-Golcher, Edwin [Univ. of California, Berkeley, CA (United States)

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 (ε_n ≤ 0.006 π· mm · mrad) although measured currents differed from the desired ones (I ~ 5mA) by about a factor of 10.

Variations in the magnetopause current layer

Science.gov (United States)

Laakso, H. E.; Middleton, H. R.

2017-12-01

We use multi-point observations from the Cluster spacecraft to investigate the variations in the magnetopause current layer. With help of the curlometer technique one can determine the magnetopause current and its variability. Most of the time the magnetopause location is moving back and forth, so during any given pass the current layer is crossed several times. We use such crossings to investigate the characteristics of the current layer as the solar wind pressure varies (and the magnetopause moves accordingly). In addition we take an advantage of the ambient electron measurements from the EDI experiment which have been calibrated against the PEACE electron spectrometer data. These data can be used to detect fast variations of 1 keV electrons at resolution of 1-100 ms. Overall, Cluster observations are highly complimentary to the MMS observations due to the polar orbit of the Cluster spacecraft which provide fast vertical profiles of the magnetopause current layer.

Use of high flip angle in T1-prepared FAST sequences for myocardial perfusion quantification

International Nuclear Information System (INIS)

Vallee, Jean-Paul; Ivancevic, Marko; Lazeyras, Francois; Didier, Dominique; Kasuboski, Larry; Chatelain, Pascal; Righetti, Alberto

2003-01-01

This study reports on the first use of high flip angle and radio-frequency (RF) spoiling in T1-prepared fast acquisition in steady state (FAST) sequence for myocardial perfusion in patients. T1 dynamic range was measured in vitro with a FAST, an RF FAST and a snapshot fast low-angle shot (FLASH) sequences with a 90 flip angle. Myocardial perfusion was then measured twice in 6 patients during the same MR session. The RF FAST and FLASH, but not the FAST sequence, demonstrated an extended T1 dynamic range; however, the FLASH images were degraded by artifacts not present on the RF FAST images. The myocardial perfusion indices K1 (first-order transfer constant from the blood to the myocardium for the Gd-DTPA) and Vd (distribution volume of Gd-DTPA in myocardium) did not differ significantly between the two injections. K1 was 0.48±0.12 ml/min g -1 and Vd was 12.5±2.9%. With an extended T1 dynamic range and the sensitivity required for myocardial perfusion quantification, the RF FAST sequence with a 90 flip angle outperformed the snapshot FLASH sequence in terms of image quality and the FAST sequence in terms of contrast dynamic range. (orig.)

Fast pulse discriminator for photon counting at high photon densities

International Nuclear Information System (INIS)

Benoit, R.; Pedrini, A.

1977-03-01

A fast tunnel diode discriminator for photon counting up to 200MHz count frequency is described. The tunnel diode is operated on its apparent I.V. characteristics displayed when the diode is driven into its oscillating region. The pulse shaper-discriminator is completely D.C. coupled in order to avoid base-line shift at high pulse rates

Structure and relative importance of ponderomotive forces and current drive generated by converted fast waves in pre-heated low aspect ratio tokamaks

Energy Technology Data Exchange (ETDEWEB)

Cuperman, S.; Bruma, C.; Komoshvili, K

2003-05-12

The generation in low aspect ratio tokamaks (LARTs) of ponderomotive forces and non-inductive current drive by the resonant fast wave-plasma interaction with mode conversion to kinetic Alfven waves (KAWs) and subsequent deposition, mainly by resonant electron Landau damping, is considered. The calculations follow the rigorous solution of the full wave equations upon using a dielectric tensor operator consisting of (i) a parallel conductivity including both kinetic effects (collisionless Landau damping on passing electrons) and collisional damping on both trapped electrons and passing electrons+ions and (ii) perpendicular components provided by the resistive two-fluid model equations. The fast waves are launched by an antenna located on the low field side and extending {+-}45 deg. about the equatorial plane. A parametric investigation of the structure and importance of the various components of the ponderomotive forces and current drive generated in START-like plasmas is carried out and their suitability for supplementing the required non-rf toroidal equilibrium current is demonstrated.

Properties of high current RFQ injectors

International Nuclear Information System (INIS)

Schempp, A.; Goethe, J.W.

1996-01-01

RFQ linacs are efficient, compact low energy ion structures, which have found numerous applications. They use electrical rf focusing and can capture, bunch and transmit high current ion beams. Some recent development and new projects like a heavy ion injectors for a cyclotron, and the status of the work on high current high duty factor RFQs will be discussed. (author)

Properties of high current RFQ injectors

Energy Technology Data Exchange (ETDEWEB)

Schempp, A.; Goethe, J.W. [Frankfurt Univ. (Germany). Inst. fuer Angewandte Physik

1996-12-31

RFQ linacs are efficient, compact low energy ion structures, which have found numerous applications. They use electrical rf focusing and can capture, bunch and transmit high current ion beams. Some recent development and new projects like a heavy ion injectors for a cyclotron, and the status of the work on high current high duty factor RFQs will be discussed. (author) 2 refs.

High temperature fast reactor for hydrogen production in Brazil; Reator nuclear rapido de altissima temperatura para producao de hidrogenio no Brasil

Energy Technology Data Exchange (ETDEWEB)

Nascimento, Jamil A. do; Ono, Shizuca; Guimaraes, Lamartine N.F. [Centro Tecnico Aeroespacial (CTA-IEAv), Sao Jose dos Campos, SP (Brazil). Inst. de Estudos Avancados]. E-mail: jamil@ieav.cta.br

2008-07-01

The main nuclear reactors technology for the Generation IV, on development phase for utilization after 2030, is the fast reactor type with high temperature output to improve the efficiency of the thermo-electric conversion process and to enable applications of the generated heat in industrial process. Currently, water electrolysis and thermo chemical cycles using very high temperature are studied for large scale and long-term hydrogen production, in the future. With the possible oil scarcity and price rise, and the global warming, this application can play an important role in the changes of the world energy matrix. In this context, it is proposed a fast reactor with very high output temperature, {approx} 1000 deg C. This reactor will have a closed fuel cycle; it will be cooled by lead and loaded with nitride fuel. This reactor may be used for hydrogen, heat and electricity production in Brazil. It is discussed a development strategy of the necessary technologies and some important problems are commented. The proposed concept presents characteristics that meet the requirements of the Generation IV reactor class. (author)

'Leak Current' correction for critical current measurement of no-insulation HTS coil

Energy Technology Data Exchange (ETDEWEB)

Song, Jung Bin [Laboratoire National des Champs Magnétiques Intenses, CNRS, Grenoble (France); Hahn, Seung Yong [Dept. of Electrical and Computer Engineering, Seoul National University, Seoul (Korea, Republic of)

2017-06-15

Discrepancy between a power supply current and an actual “spiral” coil current makes the conventional 4-probe measurement of a critical current (I{sub c}) of a no-insulation (NI) high temperature superconductor (HTS) coil inaccurate and time-consuming. This paper presents a fast and accurate approach for I{sub c} measurement of NI HTS coils. With an NI HTS coil energized at a constant ramping rate, a complete analytic expression for the spiral coil current was obtained from a first-order partial differential equation that derived from an equivalent circuit model of the NI coil. From the analytic solution, both spiral coil current and radial leak current can be obtained simultaneously, which enables fast and accurate measurement of the NI coil I{sub c}. To verify the proposed approach, an NI double-pancake (DP) coil, wound with GdBCO tapes of 6 mm × 0.1 mm, was constructed and its Ic was repeatedly measured with various ramping rates in a bath of liquid nitrogen at 77 K. The measured results agreed well with the calculated ones, which validates the proposed approach to measure I{sub c} of an NI HTS coil.

Nuclear attenuation of fast hadrons produced in charged-current ν and anti ν interactions in neon

International Nuclear Information System (INIS)

Burkot, W.; Coghen, T.; Czyzewski, J.

1996-01-01

The production of hadrons in charged-current (anti)neutrino interactions is studied with the bubble chamber BEBC exposed to the CERN (anti)neutrino wide-band beam. Fast-hadron production in a neon target is found to be attenuated as compared to that in a hydrogen target. This feature is discussed within theoretical models based on the idea of a hadron formation length. The experimental results favour the 'constituent' over the 'yo-yo' length concept, and suggest a quark cross section in the order of 3 mb. (orig.)

Turbulence Scattering of High Harmonic Fast Waves

International Nuclear Information System (INIS)

M. Ono; J. Hosea; B. LeBlanc; J. Menard; C.K. Phillips; R. Wilson; P. Ryan; D. Swain; J. Wilgen; S. Kubota; and T.K. Mau

2001-01-01

Effect of scattering of high-harmonic fast-magnetosonic waves (HHFW) by low-frequency plasma turbulence is investigated. Due to the similarity of the wavelength of HHFW to that of the expected low-frequency turbulence in the plasma edge region, the scattering of HHFW can become significant under some conditions. The scattering probability increases with the launched wave parallel-phase-velocity as the location of the wave cut-off layer shifts toward the lower density edge. The scattering probability can be reduced significantly with higher edge plasma temperature, steeper edge density gradient, and magnetic field. The theoretical model could explain some of the HHFW heating observations on the National Spherical Torus Experiment (NSTX)

Fast-wave ion cyclotron current drive for ITER and prospects for near-term proof-of-principle experiments

International Nuclear Information System (INIS)

Swain, D.W.; Batchelor, D.B.; Carter, M.D.; Jaeger, E.F.; Ryan, P.M.; Hoffman, D.J.

1989-01-01

Low-frequency fast-wave current drive (FWCD) with frequencies in the range from 30 to 100 MHz looks promising for current drive in ITER. Its theoretical efficiencies are comparable to other current-drive techniques, and it could be significantly cheaper than other proposed current drive methods because of the ready availability of inexpensive (<$1/W), efficient, multi-megawatt rf power sources. The most critical issues for FWCD are concerns about the acceptability and survivability of an appropriate antenna launching system and the lack of an experimental demonstration of FWCD in a large tokamak. We describe an antenna array that is flush with the first wall of ITER and should be able to survive in the plasma environment, present theoretical calculations of FWCD in ITER, and show results from a brief survey of some present-day tokamaks in which it might be possible to carry out FWCD proof-of-principle experiments. 4 refs., 5 figs., 1 tab

Neighborhood fast food restaurants and fast food consumption: a national study.

Science.gov (United States)

Richardson, Andrea S; Boone-Heinonen, Janne; Popkin, Barry M; Gordon-Larsen, Penny

2011-07-08

Recent studies suggest that neighborhood fast food restaurant availability is related to greater obesity, yet few studies have investigated whether neighborhood fast food restaurant availability promotes fast food consumption. Our aim was to estimate the effect of neighborhood fast food availability on frequency of fast food consumption in a national sample of young adults, a population at high risk for obesity. We used national data from U.S. young adults enrolled in wave III (2001-02; ages 18-28) of the National Longitudinal Study of Adolescent Health (n = 13,150). Urbanicity-stratified multivariate negative binomial regression models were used to examine cross-sectional associations between neighborhood fast food availability and individual-level self-reported fast food consumption frequency, controlling for individual and neighborhood characteristics. In adjusted analysis, fast food availability was not associated with weekly frequency of fast food consumption in non-urban or low- or high-density urban areas. Policies aiming to reduce neighborhood availability as a means to reduce fast food consumption among young adults may be unsuccessful. Consideration of fast food outlets near school or workplace locations, factors specific to more or less urban settings, and the role of individual lifestyle attitudes and preferences are needed in future research.

Neighborhood fast food restaurants and fast food consumption: A national study

Directory of Open Access Journals (Sweden)

Gordon-Larsen Penny

2011-07-01

Full Text Available Abstract Background Recent studies suggest that neighborhood fast food restaurant availability is related to greater obesity, yet few studies have investigated whether neighborhood fast food restaurant availability promotes fast food consumption. Our aim was to estimate the effect of neighborhood fast food availability on frequency of fast food consumption in a national sample of young adults, a population at high risk for obesity. Methods We used national data from U.S. young adults enrolled in wave III (2001-02; ages 18-28 of the National Longitudinal Study of Adolescent Health (n = 13,150. Urbanicity-stratified multivariate negative binomial regression models were used to examine cross-sectional associations between neighborhood fast food availability and individual-level self-reported fast food consumption frequency, controlling for individual and neighborhood characteristics. Results In adjusted analysis, fast food availability was not associated with weekly frequency of fast food consumption in non-urban or low- or high-density urban areas. Conclusions Policies aiming to reduce neighborhood availability as a means to reduce fast food consumption among young adults may be unsuccessful. Consideration of fast food outlets near school or workplace locations, factors specific to more or less urban settings, and the role of individual lifestyle attitudes and preferences are needed in future research.

Scanning fast and slow: current limitations of 3 Tesla functional MRI and future potential

Directory of Open Access Journals (Sweden)

Roland N Boubela

2014-02-01

Full Text Available Functional MRI at 3T has become a workhorse for the neurosciences, e.g., neurology, psychology, and psychiatry, enabling non-invasive investigation of brain function and connectivity. However, BOLD-based fMRI is a rather indirect measure of brain function, confounded by fluctuation related signals, e.g. head or brain motion, brain pulsation, blood flow, intermixed with susceptibility differences close or distant to the region of neuronal activity. Even though a plethora of preprocessing strategies have been published to address these confounds, their efficiency is still under discussion. In particular, physiological signal fluctuations closely related to brain supply may mask BOLD signal changes related to true neuronal activation. Here we explore recent technical and methodological advancements aimed at disentangling the various components, employing fast multiband vs. standard EPI, in combination with fast temporal ICA.Our preliminary results indicate that fast (TR< 0.5s scanning may help to identify and eliminate physiologic components, increasing tSNR and functional contrast. In addition, biological variability can be studied and task performance better correlated to other measures. This should increase specificity and reliability in fMRI studies. Furthermore, physiological signal changes during scanning may then be recognized as a source of information rather than a nuisance. As we are currently still undersampling the complexity of the brain, even at a rather coarse macroscopic level, we should be very cautious in the interpretation of neuroscientific findings, in particular when comparing different groups (e.g., age, sex, medication, pathology, etc.. From a technical point of view our goal should be to sample brain activity at layer specific resolution with low TR, covering as much of the brain as possible without violating SAR limits. We hope to stimulate discussion towards a better understanding and a more quantitative use of fMRI.

Determinants of Fast Food Consumption among Iranian High School Students Based on Planned Behavior Theory

Directory of Open Access Journals (Sweden)

Gholamreza Sharifirad

2013-01-01

Full Text Available Objective. This study was conducted to identify some factors (beliefs and norms which are related to fast food consumption among high school students in Isfahan, Iran. We used the framework of the theory planned behavior (TPB to predict this behavior. Subjects & Methods. Cross-sectional data were available from high school students who were recruited by cluster randomized sampling. All of the students completed a questionnaire assessing variables of standard TPB model including attitude, subjective norms, perceived behavior control (PBC, and the additional variables past behavior, actual behavior control (ABC. Results. The TPB variables explained 25.7% of the variance in intentions with positive attitude as the strongest (, and subjective norms as the weakest (, determinant. Concurrently, intentions accounted for 6% of the variance for fast food consumption. Past behavior and ABC accounted for an additional amount of 20.4% of the variance in fast food consumption. Conclusion. Overall, the present study suggests that the TPB model is useful in predicting related beliefs and norms to the fast food consumption among adolescents. Subjective norms in TPB model and past behavior in TPB model with additional variables (past behavior and actual behavior control were the most powerful predictors of fast food consumption. Therefore, TPB model may be a useful framework for planning intervention programs to reduce fast food consumption by students.

Determinants of Fast Food Consumption among Iranian High School Students Based on Planned Behavior Theory

Science.gov (United States)

Sharifirad, Gholamreza; Yarmohammadi, Parastoo; Azadbakht, Leila; Morowatisharifabad, Mohammad Ali; Hassanzadeh, Akbar

2013-01-01

Objective. This study was conducted to identify some factors (beliefs and norms) which are related to fast food consumption among high school students in Isfahan, Iran. We used the framework of the theory planned behavior (TPB) to predict this behavior. Subjects & Methods. Cross-sectional data were available from high school students (n = 521) who were recruited by cluster randomized sampling. All of the students completed a questionnaire assessing variables of standard TPB model including attitude, subjective norms, perceived behavior control (PBC), and the additional variables past behavior, actual behavior control (ABC). Results. The TPB variables explained 25.7% of the variance in intentions with positive attitude as the strongest (β = 0.31, P intentions accounted for 6% of the variance for fast food consumption. Past behavior and ABC accounted for an additional amount of 20.4% of the variance in fast food consumption. Conclusion. Overall, the present study suggests that the TPB model is useful in predicting related beliefs and norms to the fast food consumption among adolescents. Subjective norms in TPB model and past behavior in TPB model with additional variables (past behavior and actual behavior control) were the most powerful predictors of fast food consumption. Therefore, TPB model may be a useful framework for planning intervention programs to reduce fast food consumption by students. PMID:23936635

Heating and current drive on NSTX

International Nuclear Information System (INIS)

Wilson, J.R.; Batchelor, D.; Carter, M.; Hosea, J.; Ignat, D.; LeBlanc, B.; Majeski, R.; Ono, M.; Phillips, C.K.; Rogers, J.H.; Schilling, G.

1997-01-01

Low aspect ratio tokamaks pose interesting new challenges for heating and current drive. The NSTX (National Spherical Tokamak Experiment) device to be built at Princeton is a low aspect ratio toroidal device that has the achievement of high toroidal beta (∼45%) and non-inductive operation as two of its main research goals. To achieve these goals significant auxiliary heating and current drive systems are required. Present plans include ECH (Electron cyclotron heating) for pre-ionization and start-up assist, HHFW (high harmonic fast wave) for heating and current drive and eventually NBI (neutral beam injection) for heating, current drive and plasma rotation. copyright 1997 American Institute of Physics

Filtering and Control of High Speed Motor Current in a Flywheel Energy Storage System

Science.gov (United States)

Kenny, Barbara H.; Santiago, Walter

2004-01-01

The NASA Glenn Research Center has been developing technology to enable the use of high speed flywheel energy storage units in future spacecraft for the last several years. An integral part of the flywheel unit is the three phase motor/generator that is used to accelerate and decelerate the flywheel. The motor/generator voltage is supplied from a pulse width modulated (PWM) inverter operating from a fixed DC voltage supply. The motor current is regulated through a closed loop current control that commands the necessary voltage from the inverter to achieve the desired current. The current regulation loop is the innermost control loop of the overall flywheel system and, as a result, must be fast and accurate over the entire operating speed range (20,000 to 60,000 rpm) of the flywheel. The voltage applied to the motor is a high frequency PWM version of the DC bus voltage that results in the commanded fundamental value plus higher order harmonics. Most of the harmonic content is at the switching frequency and above. The higher order harmonics cause a rapid change in voltage to be applied to the motor that can result in large voltage stresses across the motor windings. In addition, the high frequency content in the motor causes sensor noise in the magnetic bearings that leads to disturbances for the bearing control. To alleviate these problems, a filter is used to present a more sinusoidal voltage to the motor/generator. However, the filter adds additional dynamics and phase lag to the motor system that can interfere with the performance of the current regulator. This paper will discuss the tuning methodology and results for the motor/generator current regulator and the impact of the filter on the control. Results at speeds up to 50,000 rpm are presented.

Fast Mapping Across Time: Memory Processes Support Children's Retention of Learned Words

Directory of Open Access Journals (Sweden)

Haley eVlach

2012-02-01

Full Text Available Children's remarkable ability to map linguistic labels to objects in the world is referred to as fast mapping. The current study examined children's (N = 216 and adults’ (N = 54 retention of fast-mapped words over time (immediately, after a 1 week delay, and after a 1 month delay. The fast mapping literature often characterizes children's retention of words as consistently high across timescales. However, the current study demonstrates that learners forget word mappings at a rapid rate. Moreover, these patterns of forgetting parallel forgetting functions of domain general memory processes. Memory processes are critical to children's word learning and the role of one such process, forgetting, is discussed in detail—forgetting supports both word mapping and the generalization of words and categories.

Fast Mapping Across Time: Memory Processes Support Children's Retention of Learned Words.

Science.gov (United States)

Vlach, Haley A; Sandhofer, Catherine M

2012-01-01

Children's remarkable ability to map linguistic labels to referents in the world is commonly called fast mapping. The current study examined children's (N = 216) and adults' (N = 54) retention of fast-mapped words over time (immediately, after a 1-week delay, and after a 1-month delay). The fast mapping literature often characterizes children's retention of words as consistently high across timescales. However, the current study demonstrates that learners forget word mappings at a rapid rate. Moreover, these patterns of forgetting parallel forgetting functions of domain-general memory processes. Memory processes are critical to children's word learning and the role of one such process, forgetting, is discussed in detail - forgetting supports extended mapping by promoting the memory and generalization of words and categories.

High-Resolution Fast-Neutron Spectrometry for Arms Control and Treaty Verification

Energy Technology Data Exchange (ETDEWEB)

David L. Chichester; James T. Johnson; Edward H. Seabury

2012-07-01

Many nondestructive nuclear analysis techniques have been developed to support the measurement needs of arms control and treaty verification, including gross photon and neutron counting, low- and high-resolution gamma spectrometry, time-correlated neutron measurements, and photon and neutron imaging. One notable measurement technique that has not been extensively studied to date for these applications is high-resolution fast-neutron spectrometry (HRFNS). Applied for arms control and treaty verification, HRFNS has the potential to serve as a complimentary measurement approach to these other techniques by providing a means to either qualitatively or quantitatively determine the composition and thickness of non-nuclear materials surrounding neutron-emitting materials. The technique uses the normally-occurring neutrons present in arms control and treaty verification objects of interest as an internal source of neutrons for performing active-interrogation transmission measurements. Most low-Z nuclei of interest for arms control and treaty verification, including 9Be, 12C, 14N, and 16O, possess fast-neutron resonance features in their absorption cross sections in the 0.5- to 5-MeV energy range. Measuring the selective removal of source neutrons over this energy range, assuming for example a fission-spectrum starting distribution, may be used to estimate the stoichiometric composition of intervening materials between the neutron source and detector. At a simpler level, determination of the emitted fast-neutron spectrum may be used for fingerprinting 'known' assemblies for later use in template-matching tests. As with photon spectrometry, automated analysis of fast-neutron spectra may be performed to support decision making and reporting systems protected behind information barriers. This paper will report recent work at Idaho National Laboratory to explore the feasibility of using HRFNS for arms control and treaty verification applications, including simulations

A small modular fast reactor as starting point for industrial deployment of fast reactors

International Nuclear Information System (INIS)

Chang, Yoon I.; Lo Pinto, Pierre; Konomura, Mamoru

2006-01-01

The current commercial reactors based on light water technology provide 17% of the electricity worldwide owing to their reliability, safety and competitive economics. In the near term, next generation reactors are expected to be evolutionary type, taking benefits of extensive LWR experience feedbacks and further improved economics and safety provisions. For the long term, however, sustainable energy production will be required due to continuous increase of the human activities, environmental concerns such as greenhouse effect and the need of alternatives to fossil fuels as long term energy resources. Therefore, future generation commercial reactors should meet some criteria of sustainability that the current generation cannot fully satisfy. In addition to the current objectives of economics and safety, waste management, resource extension and public acceptance become other major objectives among the sustainability criteria. From this perspective, two questions can be raised: what reactor type can meet the sustainability criteria, and how to proceed to an effective deployment in harmony with the high reliability and availability of the current nuclear reactor fleet. There seems to be an international consensus that the fast spectrum reactor, notably the sodium-cooled system is most promising to meet all of the long term sustainability criteria. As for the latter, we propose a small modular fast reactor project could become a base to prepare the industrial infrastructure. The paper has the following contents: - Introduction; - SMFR project; - Core design; - Supercritical CO 2 Brayton cycle; - Near-term reference plant; - Advanced designs; - Conclusions. To summarize, the sodium-cooled fast reactor is currently recognized as the technology of choice for the long term nuclear energy expansion, but some research and development are required to optimize and validate advanced design solutions. A small modular fast reactor can satisfy some existing near-term market niche

A fast isotope switching system for high energy ions

International Nuclear Information System (INIS)

Niklaus, T.R.; Sie, S.H.; Suter, G.F.

1998-01-01

A fast bouncing system for the high energy end of an Accelerator Mass Spectrometry system has been devised for the AUSTRALIS at the CSIRO HIAF laboratory. Based on a method designed for excitation function measurements, it has been adapted as an isotope sequencer for AMS at the high energy side. In this scheme, different isotopes of the same energy are deflected off axis in the orbit plane by varying amounts at the entrance to the magnet and returned to the main axis at the exit by another deflection of the same magnitude in the same plane. Synchronised with the low energy side bouncer, the system will enable isotope ratios measurements with high precision by overcoming drifts in the source, beam transport and the accelerator itself

Assessment of the thorium and uranium fuel cycle in the fast breeder and the high temperature reactor

International Nuclear Information System (INIS)

Schikorr, W.M.

1977-01-01

This report assesses the fissile fuel economy of the uranium and thorium cycle in the advanced reactors currently under development, the fast breeder reactor (FBR) and the high temperature reactor (HTR). It is shown by means of detailed burnup calculations that replacing UO 2 with ThO 2 or Th-metal as the radial blanket breeding material will not have any significant imapct on the breeding and burnup properties of the FBR. A global, analytical investigation is performed to study the fissile fuel economy of the many fissile fuel cycles possible in the HTR. Here it is demonstrated that the optimum conversion ratio of CR 3 O 8 ) demands are evaluated for a country such as the FRG under the assumptions of different future reactor strategy scenarios. Here it is demonstrated that the employement of both HTRs and FBRs can lead to a practically resource independent energy supply system within the next 40 to 60 years. However only through the large scale employement of the fast breeder can the future nuclear resource requirements be assured. (orig.) [de

Stable operating regimes in NET with respect to Alfven wave instabilities during neutral beam current drive

International Nuclear Information System (INIS)

Eckhartt, D.

1989-01-01

Supra-thermal ions can contribute to the steady-state current in future large tokamak machines like NET or ITER. The fast-ion population is generated by collisional slowing-down of high-energy ions which were injected as neutral atoms in quasi-tangential direction and ionized by plasma interactions. Depending on the initial beam shape these fast ions can excite microinstabilities of the Alfven-wave type which are driven by the gradients in velocity-space. The ensuring plasma turbulence is expected to slow down the fast ions very quickly. This effect reduces the current drive efficiency which otherwise is comparable to that of other current drive schemes like lower hybrid waves where the toroidal current is carried by high-energy resonant electrons. (author) 3 refs., 1 fig

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

International Nuclear Information System (INIS)

Chacon-Golcher, E.

2002-01-01

This dissertation develops diverse research on small (diameter ∼ few mm), high current density (J ∼ several tens of mA/cm 2 ) 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/cm 2 were observed in 2.3 (micro)s 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 (micro)s), high current densities (∼ 100 mA/cm 2 ) and low operating pressures ( e psilon) n (le) 0.006 π mm · mrad) although measured currents differed from the desired ones (I ∼ 5mA) by about a factor of 10

Differences in perceptions and fast food eating behaviours between Indians living in high- and low-income neighbourhoods of Chandigarh, India.

Science.gov (United States)

Aloia, Christopher Robert; Gasevic, Danijela; Yusuf, Salim; Teo, Koon; Chockalingam, Arun; Patro, Binod Kumar; Kumar, Rajesh; Lear, Scott Alexander

2013-01-07

Increased density of fast food restaurants is associated with increased prevalence of obesity in developed countries. However, less is known about this relationship in developing countries undergoing rapid urbanization and how differences in neighbourhood income affect the patronage of fast food outlets. The purpose of the study is to explore the differences in fast food preferences, perceptions, and patronage between Indians living in high- and low-income neighbourhoods. This cross-sectional study recruited 204 men and women (35 to 65 years in age) from high- and low-income neighbourhoods who completed a questionnaire on fast food consumption. The questionnaire asked participants to define fast food and to provide reasons for and frequency of visits to fast food restaurants. The differences were analyzed using Chi square and t-tests for categorical and continuous variables, respectively. Participants from a high-income neighbourhood were more likely to perceive Western -style fast food as fast food, while people from the low-income neighbourhood were more likely to identify food sold by street vendors as fast food (p food from street vendors while less likely to dine out at both fast food and non-fast food restaurants (pfood restaurants than their low-income neighbourhood counterparts, there were no significant differences in the reasons for visiting fast food restaurants (convenience, price, social enjoyment, and quality of meals) between the two groups. Both groups preferred home cooked over restaurant meals, and they recognized that home cooked food was healthier. Overall, consumption of fast food was low. People from a high-income neighbourhood dined out more frequently and were more likely to perceive Western-style food as fast food compared to their counterparts from the low-income neighbourhood.

Fast Spectrum Reactors

CERN Document Server

Todd, Donald; Tsvetkov, Pavel

2012-01-01

Fast Spectrum Reactors presents a detailed overview of world-wide technology contributing to the development of fast spectrum reactors. With a unique focus on the capabilities of fast spectrum reactors to address nuclear waste transmutation issues, in addition to the well-known capabilities of breeding new fuel, this volume describes how fast spectrum reactors contribute to the wide application of nuclear power systems to serve the global nuclear renaissance while minimizing nuclear proliferation concerns. Readers will find an introduction to the sustainable development of nuclear energy and the role of fast reactors, in addition to an economic analysis of nuclear reactors. A section devoted to neutronics offers the current trends in nuclear design, such as performance parameters and the optimization of advanced power systems. The latest findings on fuel management, partitioning and transmutation include the physics, efficiency and strategies of transmutation, homogeneous and heterogeneous recycling, in addit...

Anthropometric, biomechanical, and isokinetic strength predictors of ball release speed in high-performance cricket fast bowlers.

Science.gov (United States)

Wormgoor, Shohn; Harden, Lois; Mckinon, Warrick

2010-07-01

Fast bowling is fundamental to all forms of cricket. The purpose of this study was to identify parameters that contribute to high ball release speeds in cricket fast bowlers. We assessed anthropometric dimensions, concentric and eccentric isokinetic strength of selected knee and shoulder muscle groups, and specific aspects of technique from a single delivery in 28 high-performance fast bowlers (age 22.0 +/- 3.0 years, ball release speed 34.0 +/- 1.3 m s(-1)). Six 50-Hz cameras and the Ariel Performance Analysis System software were used to analyse the fast and accurate deliveries. Using Pearson's correlation, parameters that showed significant associations with ball release speed were identified. The findings suggest that greater front leg knee extension at ball release (r=0.52), shoulder alignment in the transverse plane rotated further away from the batsman at front foot strike (r=0.47), greater ankle height during the delivery stride (r=0.44), and greater shoulder extension strength (r=0.39) contribute significantly to higher ball release speeds. Predictor variables failed to allow their incorporation into a multivariate model, which is known to exist in less accomplished bowlers, suggesting that factors that determine ball release speed found in other groups may not apply to high-performance fast bowlers.

FAST Plasma Scenarios and Equilibrium Configurations

International Nuclear Information System (INIS)

Calabro, G.; Crisanti, F.; Ramogida, G.; Cardinali, A.; Cucchiaro, A.; Maddaluno, G.; Pizzuto, A.; Pericoli Ridolfini, V.; Tuccillo, A.A.; Zonca, F.; Albanese, R.; Granucci, G.; Nowak, S.

2008-01-01

In this paper we present the Fusion Advanced Studies Torus (FAST) plasma scenarios and equilibrium configurations, designed to reproduce the ITER ones (with scaled plasma current) and suitable to fulfil plasma conditions for integrated studies of burning plasma physics, Plasma Wall interaction, ITER relevant operation problems and Steady State scenarios. The attention is focused on FAST flexibility in terms of both performance and physics that can be investigated: operations are foreseen at a wide range of parameters from high performance H-Mode (toroidal field, B T , up to 8.5 T; plasma current, I P , up to 8 MA) to advanced tokamak (AT) operation (I P =3 MA) as well as full non inductive current scenario (I P =2 MA). The coupled heating power is provided with 30MW delivered by an Ion Cyclotron Resonance Heating (ICRH) system (30-90MHz), 6 MW by a Lower Hybrid (LH) system (3.7 or 5 GHz) for the long pulse AT scenario, 4 MW by an Electron Cyclotron Resonant Heating (ECRH) system (170 GHz-B T =6T) for MHD and electron heating localized control and, eventually, with 10 MW by a Negative Ion Beam (NNBI), which the ports are designed to accommodate. In the reference H-mode scenario FAST preserves (with respect to ITER) fast ions induced as well as turbulence fluctuation spectra, thus, addressing the cross-scale couplings issue of micro- to meso-scale physics. The noninductive scenario at I P =2MA is obtained with 60-70 % of bootstrap and the remaining by LHCD. Predictive simulations of the H-mode scenarios described above have been performed by means of JETTO code, using a semi-empirical mixed Bohm/gyro-Bohm transport model. Plasma position and Shape Control studies are also presented for the reference scenario

Low-frequency current drive and helicity injection

International Nuclear Information System (INIS)

Chan, V.S.; Miller, R.L.; Ohkawa, T.

1990-01-01

For ω much-lt Ω i , where Ω i is the ion cyclotron frequency, circularly polarized waves can drive current far exceeding the current resulting from linearly polarized waves. Further, the efficiency can be independent of plasma density. In some cases, this circular polarization may be interpreted in terms of helicity injection. For tokamak applications, where the wavenumber in the toroidal direction is a real quantity, wave helicity is injected only with finite E z waves, where z is the direction of the static magnetic field. The Alfven waves are possible current drive candidates but, in the cylindrical model considered, the compressional wave is weakly damped because E z =0, while the shear Alfven wave is totally absorbed at the surface because of finite E z . A mixture of the two modes is shown to drive an oscillatory surface current even though the efficiency is high and independent of density. A more promising current drive candidate is a fast wave that propagates to the plasma interior and is damped by the minority cyclotron resonance. Near the minority mode conversion region, the fast wave is left-handed circularly polarized and it has a small but finite E z component at high electron temperatures. The current drive efficiency, although not as high as that of the Alfven wave, is still good and independent of density, making it attractive for fusion reactors

Fast Breeder Reactor studies

International Nuclear Information System (INIS)

Till, C.E.; Chang, Y.I.; Kittel, J.H.; Fauske, H.K.; Lineberry, M.J.; Stevenson, M.G.; Amundson, P.I.; Dance, K.D.

1980-07-01

This report is a compilation of Fast Breeder Reactor (FBR) resource documents prepared to provide the technical basis for the US contribution to the International Nuclear Fuel Cycle Evaluation. The eight separate parts deal with the alternative fast breeder reactor fuel cycles in terms of energy demand, resource base, technical potential and current status, safety, proliferation resistance, deployment, and nuclear safeguards. An Annex compares the cost of decommissioning light-water and fast breeder reactors. Separate abstracts are included for each of the parts

Fast Breeder Reactor studies

Energy Technology Data Exchange (ETDEWEB)

Till, C.E.; Chang, Y.I.; Kittel, J.H.; Fauske, H.K.; Lineberry, M.J.; Stevenson, M.G.; Amundson, P.I.; Dance, K.D.

1980-07-01

This report is a compilation of Fast Breeder Reactor (FBR) resource documents prepared to provide the technical basis for the US contribution to the International Nuclear Fuel Cycle Evaluation. The eight separate parts deal with the alternative fast breeder reactor fuel cycles in terms of energy demand, resource base, technical potential and current status, safety, proliferation resistance, deployment, and nuclear safeguards. An Annex compares the cost of decommissioning light-water and fast breeder reactors. Separate abstracts are included for each of the parts.

Neighborhood fast food restaurants and fast food consumption: A national study

OpenAIRE

Richardson, Andrea S; Boone-Heinonen, Janne; Popkin, Barry M; Gordon-Larsen, Penny

2011-01-01

Abstract Background Recent studies suggest that neighborhood fast food restaurant availability is related to greater obesity, yet few studies have investigated whether neighborhood fast food restaurant availability promotes fast food consumption. Our aim was to estimate the effect of neighborhood fast food availability on frequency of fast food consumption in a national sample of young adults, a population at high risk for obesity. Methods We used national data from U.S. young adults enrolled...

Monitoring the fast neutrons in a high flux: The case for 242Pu fission chambers

International Nuclear Information System (INIS)

Filliatre, P.; Jammes, C.; Oriol, L.; Geslot, B.; Vermeeren, L.

2009-01-01

Fission chambers are widely used for on-line monitoring of neutron fluxes in irradiation reactors. A selective measurement of a component of interest of the neutron flux is possible in principle thanks to a careful choice of the deposit material. However, measuring the fast component is challenging when the flux is high (up to 10 15 n/cm 2 /s) with a significant thermal component. The main problem is that the isotopic content of a material selected for its good response to fast neutrons evolves with irradiation, so that the material is more and more sensitive to thermal neutrons. Within the framework of the FNDS (Fast Neutron Detector System) project, we design tools that simulate the evolution of the isotopic composition and fission rate for several deposits under any given flux. In the case of a high flux with a significant thermal component, 242 Pu is shown after a comprehensive study of all possibilities to be the best choice for measuring the fast component, as long as its purity is sufficient. If an estimate of the thermal flux is independently available, one can correct the signal for that component. This suggests a system of two detectors, one of which being used for such a correction. It is of very high interest when the detectors must be operated up to a high neutron fluence. (authors)

An accurate, fast, and scalable solver for high-frequency wave propagation

Science.gov (United States)

Zepeda-Núñez, L.; Taus, M.; Hewett, R.; Demanet, L.

2017-12-01

In many science and engineering applications, solving time-harmonic high-frequency wave propagation problems quickly and accurately is of paramount importance. For example, in geophysics, particularly in oil exploration, such problems can be the forward problem in an iterative process for solving the inverse problem of subsurface inversion. It is important to solve these wave propagation problems accurately in order to efficiently obtain meaningful solutions of the inverse problems: low order forward modeling can hinder convergence. Additionally, due to the volume of data and the iterative nature of most optimization algorithms, the forward problem must be solved many times. Therefore, a fast solver is necessary to make solving the inverse problem feasible. For time-harmonic high-frequency wave propagation, obtaining both speed and accuracy is historically challenging. Recently, there have been many advances in the development of fast solvers for such problems, including methods which have linear complexity with respect to the number of degrees of freedom. While most methods scale optimally only in the context of low-order discretizations and smooth wave speed distributions, the method of polarized traces has been shown to retain optimal scaling for high-order discretizations, such as hybridizable discontinuous Galerkin methods and for highly heterogeneous (and even discontinuous) wave speeds. The resulting fast and accurate solver is consequently highly attractive for geophysical applications. To date, this method relies on a layered domain decomposition together with a preconditioner applied in a sweeping fashion, which has limited straight-forward parallelization. In this work, we introduce a new version of the method of polarized traces which reveals more parallel structure than previous versions while preserving all of its other advantages. We achieve this by further decomposing each layer and applying the preconditioner to these new components separately and

Investigation of Ion Absorption of the High Harmonic Fast Wave in NSTX using HPRT

International Nuclear Information System (INIS)

Rosenberg, A.; Menard, J.E.; LeBlanc, B.P.

2001-01-01

Understanding high harmonic fast wave (HHFW) power absorption by ions in a spherical torus (ST) is of critical importance to assessing the wave's viability as a means of heating and especially driving current. In this work, the HPRT code is used to calculate absorption for helium and deuterium, with and without minority hydrogen in National Spherical Torus Experiment (NSTX) plasmas using experimental EFIT code equilibria and kinetic profiles. HPRT is a two-dimensional ray-tracing code which uses the full hot plasma dielectric to compute the perpendicular wave number along the hot electron and cold ion plasma ray path. Ion and electron absorption dependence on antenna phasing, ion temperature, beta (subscript t), and minority temperature and concentration is analyzed. These results form the basis for comparisons with other codes, such as CURRAY, METS, TORIC, and AORSA

Fast SMES for generation of high power pulses

International Nuclear Information System (INIS)

Juengst, K.P.; Salbert, H.

1996-01-01

A technique for generation of high power pulses based on a fast SMES has been developed and a model of a power modulator for linear accelerators was built. The basic function of the modulator that generates 2 ms long, approximately 1 MW power pulses at a repetition rate of 10 Hz is described in this paper. A modular construction of the SMES that consists of up to six coils has been chosen to meet the demands of several applications in high energy physics and energy distribution. The rate of change of magnetic field achieved during ramping of the magnet was more than 60 T/s without a quench. The magnet was designed with respect to the high AC losses during repetitive ramping of the SMES. The suitability of mixed matrix superconductors instead of more expensive net frequency wires for this kind of AC stress was investigated. The applied mixed matrix Cu/CuNi/NbTi wire and the construction of a single coil is described

ICON, a current model preamplifier in CMOS technology for use with high rate particle detectors

International Nuclear Information System (INIS)

Anghinolfi, F.; Aspell, P.; Campbell, M.; Heijne, E.H.M.; Jarron, P.; Meddeler, G.; Santiard, J.C.

1993-01-01

The ICON current mode preamplifier is intended for use in experiments at high rate hadron colliders. The transient response and noise performance have been analyzed. One chip has been made using an ICON circuit with resistive feedback to produce a preamplifier with a peaking time of below 10 ns. This fast preamplifier has a gain of 870 mV/pC and a power dissipation of around 1 mW. Another chip was made which uses the ICON circuit as the front-end to a dual port analog memory. The noise measured is between 2,400 e - and 3,000 e - . An important characteristic of ICON is that it can tolerate a detector leakage current of 10 μA at the DC coupled input. Therefore, it is very suitable for silicon detector systems under severe radiation conditions

High current polarized electron source

Science.gov (United States)

Suleiman, R.; Adderley, P.; Grames, J.; Hansknecht, J.; Poelker, M.; Stutzman, M.

2018-05-01

Jefferson Lab operates two DC high voltage GaAs photoguns with compact inverted insulators. One photogun provides the polarized electron beam at the Continuous Electron Beam Accelerator Facility (CEBAF) up to 200 µA. The other gun is used for high average current photocathode lifetime studies at a dedicated test facility up to 4 mA of polarized beam and 10 mA of un-polarized beam. GaAs-based photoguns used at accelerators with extensive user programs must exhibit long photocathode operating lifetime. Achieving this goal represents a significant challenge for proposed facilities that must operate in excess of tens of mA of polarized average current. This contribution describes techniques to maintain good vacuum while delivering high beam currents, and techniques that minimize damage due to ion bombardment, the dominant mechanism that reduces photocathode yield. Advantages of higher DC voltage include reduced space-charge emittance growth and the potential for better photocathode lifetime. Highlights of R&D to improve the performance of polarized electron sources and prolong the lifetime of strained-superlattice GaAs are presented.

Three-dimensional Core Design of a Super Fast Reactor with a High Power Density

International Nuclear Information System (INIS)

Cao, Liangzhi; Oka, Yoshiaki; Ishiwatari, Yuki; Ikejiri, Satoshi; Ju, Haitao

2010-01-01

The SuperCritical Water-cooled Reactor (SCWR) pursues high power density to reduce its capital cost. The fast spectrum SCWR, called a super fast reactor, can be designed with a higher power density than thermal spectrum SCWR. The mechanism of increasing the average power density of the super fast reactor is studied theoretically and numerically. Some key parameters affecting the average power density, including fuel pin outer diameter, fuel pitch, power peaking factor, and the fraction of seed assemblies, are analyzed and optimized to achieve a more compact core. Based on those sensitivity analyses, a compact super fast reactor is successfully designed with an average power density of 294.8 W/cm 3 . The core characteristics are analyzed by using three-dimensional neutronics/thermal-hydraulics coupling method. Numerical results show that all of the design criteria and goals are satisfied

High-frame rate imaging of two-phase flow in a thin rectangular channel using fast neutrons.

Science.gov (United States)

Zboray, R; Mor, I; Dangendorf, V; Stark, M; Tittelmeier, K; Cortesi, M; Adams, R

2014-08-01

We have demonstrated the feasibility of performing high-frame-rate, fast neutron radiography of air-water two-phase flows in a thin channel with rectangular cross section. The experiments have been carried out at the accelerator facility of the Physikalisch-Technische Bundesanstalt. A polychromatic, high-intensity fast neutron beam with average energy of 6 MeV was produced by 11.5 MeV deuterons hitting a thick Be target. Image sequences down to 10 ms exposure times were obtained using a fast-neutron imaging detector developed in the context of fast-neutron resonance imaging. Different two-phase flow regimes such as bubbly slug and churn flows have been examined. Two phase flow parameters like the volumetric gas fraction, bubble size and mean bubble velocities have been measured. The first results are promising, improvements for future experiments are also discussed. Copyright © 2014 Elsevier Ltd. All rights reserved.

New conceptual antenna with spiral structure and back Faraday shield for FWCD (fast wave current drive)

International Nuclear Information System (INIS)

Saigusa, M.; Moriyama, S.; Fujii, T.; Kimura, H.

1994-01-01

A new conceptual antenna, which we call as a spiral antenna, is proposed as a traveling wave antenna for fast wave current drive in tokamaks. The features of the spiral antenna are a sharp N z spectrum, easy impedance matching, N z controllable and good coupling. A back Faraday shield is proposed for improving the cooling design of Faraday shield and better antenna-plasma coupling. A helical support which is a compact and wide band support is proposed as a kind of quarter wave length stub supports. The RF properties of the spiral antenna and the back Faraday shield have been investigated by using mock-up antennas. The VSWR of spiral antenna is low at the wide frequency band from 15 MHz to 201 MHz. The back Faraday shield is effective for suppressing the RF toroidal electric field between adjacent currents straps. (author)

Fast Coordinated Control of DFIG Wind Turbine Generators for Low and High Voltage Ride-Through

DEFF Research Database (Denmark)

Wang, Yun; Wu, Qiuwei; Xu, Honghua

2014-01-01

This paper presents a fast coordinated control scheme of the rotor side converter (RSC), the DC chopper and the grid side converter (GSC) of doubly fed induction generator (DFIG) wind turbine generators (WTGs) which is to improve the low voltage ride through (LVRT) and high voltage ride through...... were proposed considering the characteristics of the DFIG WTGs during voltage changes. The fast coordinated control of RSC and GSC were developed based on the characteristic analysis in order to realize efficient LVRT and HVRT of the DFIG WTGs. The proposed fast coordinated control schemes were...

Fast photomultiplier ELUP 151

International Nuclear Information System (INIS)

Andreeva, L.I.; Belokon', V.A.; Krasin, E.V.

1992-01-01

High-velocity photomultiplier is described. The latter is recommended to be used in nuclear physics, plasma physics, nuclear medical diagnostics and at measurement of fast-occurring process parameters. Main specifications are as follows: range of spectral sensitivity - 0.2-0.7 μm; limit of dinamic characteristic linearity - up to 5A; dark current at +20 deg C ambient temperature - maximum 10-8A, time of anode pulse growth - maximum 8 ns; photocathode quantum yield in the maximum of spectral characteristic (λ max =380-420 nm) - 24-26%; supply voltage - 4-5 kV

Fast nanostructured carbon microparticle synthesis by one-step high-flux plasma processing

NARCIS (Netherlands)

Aussems, D. U. B.; Bystrov, K.; Dogan, I.; Arnas, C.; Cabié, M.; Neisius, T.; Rasinski, M.; Zoethout, E.; Lipman, P.; van de Sanden, M. C. M.; Morgan, T. W.

2017-01-01

This study demonstrates a fast one-step synthesis method for nanostructured carbon microparticles on graphite samples using high-flux plasma exposure. These structures are considered as potential candidates for energy applications such as Li-ion batteries and supercapacitors. The samples were

Fast nanostructured carbon microparticle synthesis by one-step high-flux plasma processing

NARCIS (Netherlands)

Aussems, D.U.B.; Bystrov, K.E.; Doǧan, I.; Arnas, C.; Cabié, M.; Neisius, T.; Rasinski, M.; Lipman, P.J.L.; van de Sanden, M.C.M.; Morgan, T.W.

This study demonstrates a fast one-step synthesis method for nanostructured carbon microparticles on graphite samples using high-flux plasma exposure. These structures are considered as potential candidates for energy applications such as Li-ion batteries and supercapacitors. The samples were

A highly scalable massively parallel fast marching method for the Eikonal equation

Science.gov (United States)

Yang, Jianming; Stern, Frederick

2017-03-01

The fast marching method is a widely used numerical method for solving the Eikonal equation arising from a variety of scientific and engineering fields. It is long deemed inherently sequential and an efficient parallel algorithm applicable to large-scale practical applications is not available in the literature. In this study, we present a highly scalable massively parallel implementation of the fast marching method using a domain decomposition approach. Central to this algorithm is a novel restarted narrow band approach that coordinates the frequency of communications and the amount of computations extra to a sequential run for achieving an unprecedented parallel performance. Within each restart, the narrow band fast marching method is executed; simple synchronous local exchanges and global reductions are adopted for communicating updated data in the overlapping regions between neighboring subdomains and getting the latest front status, respectively. The independence of front characteristics is exploited through special data structures and augmented status tags to extract the masked parallelism within the fast marching method. The efficiency, flexibility, and applicability of the parallel algorithm are demonstrated through several examples. These problems are extensively tested on six grids with up to 1 billion points using different numbers of processes ranging from 1 to 65536. Remarkable parallel speedups are achieved using tens of thousands of processes. Detailed pseudo-codes for both the sequential and parallel algorithms are provided to illustrate the simplicity of the parallel implementation and its similarity to the sequential narrow band fast marching algorithm.

Wearable supercapacitors on polyethylene terephthalate fabrics with good wash fastness and high flexibility

Science.gov (United States)

Wang, Guixia; Babaahmadi, Vahid; He, Nanfei; Liu, Yixin; Pan, Qin; Montazer, Majid; Gao, Wei

2017-11-01

All solid-state micro-supercapacitors (MSC) have emerged as attractive energy-storage units for portable and wearable electronics. Here, we describe a textile-based solid-state MSC via laser scribing of graphene oxide (GO) coatings on a flexible polyethylene terephthalate (PET) fabric. The laser-scribed graphene oxide layers (LGO) possess three-dimensionally porous structure suitable for electrochemical-double-layer formation. To improve the wash fastness and the flexibility of the as-prepared MSCs, glutaraldehyde (GA) was employed to crosslink the GO layers and PVA-gel electrolyte onto the PET fabric. The resultant all solid-state MSCs exhibited excellent flexibility, high areal specific capacitance (756 μF·cm-2 at 20 mV·s-1), and good rate capability when subject to bending and laundering. Furthermore, the MSC device showed a high power density of about 1.4 W·cm-3 and an energy density of 5.3 × 10-5 Wh·cm-3, and retained 98.3% of its initial capacitance after 1000 cycles at a current density of 0.5 mA·cm-2. This work is the first demonstration of in-plane MSCs on PET fabric surfaces with enhanced durability and flexibility.

Preparative separation of flavonoids from the medicinal plant Davilla elliptica St. Hill. by high-speed counter-current chromatography

OpenAIRE

Rinaldo Daniel; Silva Marcelo Aparecido; Rodrigues Clenilson Martins; Calvo Tamara Regina; Sannomiya Miriam; Santos Lourdes Campaner dos; Vilegas Wagner; Kushima Hélio; Hiruma-Lima Clélia Akiko; Brito Alba Regina Monteiro de Souza

2006-01-01

High-speed counter-current chromatography (HSCCC) is a major tool for the fast separation of natural products from plants. It was used for the preparative isolation of the flavonoid monoglucosides present in the aerial parts of the Davilla elliptica St. Hill. (Dilleniaceae). This species is used in Brazilian folk medicine for the treatment of gastric disorders. The optimum solvent system used was composed of a mixture of ethyl acetate-n-propanol-water (140:8:80, v/v/v) and led to a successful...

A fast alignment method for breast MRI follow-up studies using automated breast segmentation and current-prior registration

Science.gov (United States)

Wang, Lei; Strehlow, Jan; Rühaak, Jan; Weiler, Florian; Diez, Yago; Gubern-Merida, Albert; Diekmann, Susanne; Laue, Hendrik; Hahn, Horst K.

2015-03-01

In breast cancer screening for high-risk women, follow-up magnetic resonance images (MRI) are acquired with a time interval ranging from several months up to a few years. Prior MRI studies may provide additional clinical value when examining the current one and thus have the potential to increase sensitivity and specificity of screening. To build a spatial correlation between suspicious findings in both current and prior studies, a reliable alignment method between follow-up studies is desirable. However, long time interval, different scanners and imaging protocols, and varying breast compression can result in a large deformation, which challenges the registration process. In this work, we present a fast and robust spatial alignment framework, which combines automated breast segmentation and current-prior registration techniques in a multi-level fashion. First, fully automatic breast segmentation is applied to extract the breast masks that are used to obtain an initial affine transform. Then, a non-rigid registration algorithm using normalized gradient fields as similarity measure together with curvature regularization is applied. A total of 29 subjects and 58 breast MR images were collected for performance assessment. To evaluate the global registration accuracy, the volume overlap and boundary surface distance metrics are calculated, resulting in an average Dice Similarity Coefficient (DSC) of 0.96 and root mean square distance (RMSD) of 1.64 mm. In addition, to measure local registration accuracy, for each subject a radiologist annotated 10 pairs of markers in the current and prior studies representing corresponding anatomical locations. The average distance error of marker pairs dropped from 67.37 mm to 10.86 mm after applying registration.

Fast and effective determination of strontium-90 in high volumes water samples

International Nuclear Information System (INIS)

Basarabova, B.; Dulanska, S.

2014-01-01

A simple and fast method was developed for determination of 90 Sr in high volumes of water samples from vicinity of nuclear power facilities. Samples were taken from the environment near Nuclear Power Plants in Jaslovske Bohunice and Mochovce in Slovakia. For determination of 90 Sr was used solid phase extraction using commercial sorbent Analig R Sr-01 from company IBC Advanced Technologies, Inc.. Determination of 90 Sr was performed with dilute solution of HNO 3 (1.5-2 M) and also tested in base medium with NaOH. For elution of 90 Sr was used eluent EDTA with pH in range 8-9. To achieve fast determination, automation was applied, which brings significant reduction of separation time. Concentration of water samples with evaporation was not necessary. Separation was performed immediately after filtration of analyzed samples. The aim of this study was development of less expensive, time unlimited and energy saving method for determination of 90 Sr in comparison with conventional methods. Separation time for fast-flow with volume of 10 dm 3 of water samples was 3.5 hours (flow-rate approximately 3.2 dm 3 / 1 hour). Radiochemical strontium yield was traced by using radionuclide 85 Sr. Samples were measured with HPGe detector (High-purity Germanium detector) at energy E φ = 514 keV. By using Analig R Sr-01 yields in range 72 - 96 % were achieved. Separation based on solid phase extraction using Analig R Sr-01 employing utilization of automation offers new, fast and effective method for determination of 90 Sr in water matrix. After ingrowth of yttrium samples were measured by Liquid Scintillation Spectrometer Packard Tricarb 2900 TR with software Quanta Smart. (authors)

The High-Potential Fast-Flying Achiever: Themes from the English Language Literature 1976-1995.

Science.gov (United States)

Altman, Yochanan

1997-01-01

Review of business management literature from the United States, United Kingdom, and Canada identified the following: the images of high flyer, fast track, and high achiever; the meaning of success; emphasis on performance; corporate rites of passage; and opportunities for women to be high flyers. (SK)

Thermal-mechanical simulation of high-current pulsed electron beam surface modification process of pure aluminum

International Nuclear Information System (INIS)

Zou Jianxin; Qin Ying; Wu Aimin; Hao Shengzhi; Wang Xiaogang; Dong Chuang

2004-01-01

A mathematical physics model is established to describe the surface modification process of High Current Pulsed Electron Beams (HCPEB) of pure aluminum alloy. Computer simulation is used to reveal the phenomena of fast heating and cooling, melting, solidification, evaporation, and thermal stress wave associated with the HCPEB bombardment. The calculated melting depth is about 1-10 μm, which is close to the experimental results. The evaporated layer is at nanometer level, which can be omitted in the calculation of temperature field. The thermal stress wave, though as weak as about 0.1 MPa in peak amplitude (proportional to pulsed energy density), has strong impacts on material's structure and properties. (authors)

Measurements of Pfirsch-Schlueter current and pressure profile for the high density ECH plasmas in Heliotron DR

International Nuclear Information System (INIS)

Morimoto, S.; Yanagi, N.; Nakasuga, M.; Obiki, T.; Iiyoshi, A.; Uo, K.

1988-01-01

The Pfirsch-Schlueter current and pressure profiles are estimated from magnetic measurements for high density electron cyclotron heating (ECH) plasmas (n-bar e =(2-3)x10 13 cm -3 , T e0 =200-400 eV, (β) 0 (1-(r/a) 2 ) s , is about two in macroscopically stable plasmas. A fast loss of plasma energy from the centre to the periphery is observed during the onset of the MHD instability. This method of measuring the pressure profile shape is simple and useful for heliotron type devices. (author). 20 refs, 8 figs, 1 tab

A lattice-gas model of the ion current across the solid interface: fast-ion conductor - intercalate

International Nuclear Information System (INIS)

Nachev, I.; Balkanski, M.

1994-12-01

The transport of Lithium ions across the material interface: fast-ion conducting glass - intercalate is simulated by a non-trivial lattice-gas model. The model takes explicitly into account the influence of the Coulomb correlations, the site-blocking effect and the boundary conditions on the ion kinetics. Potential device applications of the model are pointed out by computing the current density of Lithium ions for material parameters of the real interface: doped ternary borate glass - Indium Selenide, which constitute the electrolyte and the cathode, respectively, of a thin-film microbattery with improved performance. (author). 10 refs, 4 figs

Fast measure proceeding of weak currents; Un procede de mesure rapide des courants faibles

Energy Technology Data Exchange (ETDEWEB)

Taieb, J [Commissariat a l' Energie Atomique, Siege (France). Centre d' Etudes Nucleaires

1953-07-01

The process of fast measure of the weak currents that we are going to describe briefly apply worthy of the provided currents by the sources to elevated value internal resistance, as it is the case for the ionization chamber, the photocells, mass spectroscopic tubes. The problem to measure weak currents is essentially a problem of amplifier and of input circuit. We intended to achieve a whole amplifier and input circuit with advanced performances, meaning that for a measured celerity we wanted to have an signal/noise ratio the most important as in the classic systems and for a same report signal/noise a more quickly done measure. (M.B.) [French] Le procede de mesure rapide des courants faibles que nous allons brievement decrire s'applique a la mesure des courants fournis par les sources a resistance interne de valeur elevee, comme c'est le cas pour les chambres d'ionisation, les photocellules, les tubes de spectrographe de masse. Le probleme de mesure de courants faibles est essentiellement un probleme d'amplificateur et de circuit d'entree. Nous nous sommes proposes de realiser un ensemble amplificateur et circuit d'entree a performances poussees, c'est a dire que pour une meme rapidite de mesure nous desirions avoir un rapport signal/bruit plus important que dans les systemes classiques et pour un meme rapport signal/bruit une mesure effectuee plus rapidement. (M.B.)

Energy conversion assessment of vacuum, slow and fast pyrolysis processes for low and high ash paper waste sludge

International Nuclear Information System (INIS)

Ridout, Angelo J.; Carrier, Marion; Collard, François-Xavier; Görgens, Johann

2016-01-01

Highlights: • Vacuum, slow and fast pyrolysis of low and high ash paper waste sludge (PWS) is compared. • Reactor temperature and pellet size optimised to maximise liquid and solid product yields. • Gross energy recovery from solid and liquid was assessed. • Fast pyrolysis of low and high ash PWS offers higher energy conversions. - Abstract: The performance of vacuum, slow and fast pyrolysis processes to transfer energy from the paper waste sludge (PWS) to liquid and solid products was compared. Paper waste sludges with low and high ash content (8.5 and 46.7 wt.%) were converted under optimised conditions for temperature and pellet size to maximise both product yields and energy content. Comparison of the gross energy conversions, as a combination of the bio-oil/tarry phase and char (EC_s_u_m), revealed that the fast pyrolysis performance was between 18.5% and 20.1% higher for the low ash PWS, and 18.4% and 36.5% higher for high ash PWS, when compared to the slow and vacuum pyrolysis processes respectively. For both PWSs, this finding was mainly attributed to higher production of condensable organic compounds and lower water yields during FP. The low ash PWS chars, fast pyrolysis bio-oils and vacuum pyrolysis tarry phase products had high calorific values (∼18–23 MJ kg"−"1) making them promising for energy applications. Considering the low calorific values of the chars from alternative pyrolysis processes (∼4–7 MJ kg"−"1), the high ash PWS should rather be converted to fast pyrolysis bio-oil to maximise the recovery of usable energy products.

Development of high pressure deuterium gas targets for the generation of intense mono-energetic fast neutron beams

International Nuclear Information System (INIS)

Guzek, J.; Richardson, K.; Franklyn, C.B.; Waites, A.; McMurray, W.R.; Watterson, J.I.W.; Tapper, U.A.S.

1999-01-01

Two different technical solutions to the problem of generation of mono-energetic fast neutron beams on the gaseous targets are presented here. A simple and cost-effective design of a cooled windowed gas target system is described in the first part of this paper. It utilises a thin metallic foil window and circulating deuterium gas cooled down to 100 K. The ultimate beam handling capability of such target is determined by the properties of the window. Reliable performance of this gas target system was achieved at 1 bar of deuterium gas, when exposed to a 45 μA beam of 5 MeV deuterons, for periods in excess of 6 h. Cooling of the target gas resulted in increased fast neutron output and improved neutron to gamma-ray ratio. The second part of this paper discusses the design of a high pressure, windowless gas target for use with pulsed, low duty cycle accelerators. A rotating seal concept was applied to reduce the gas load in a differentially pumped system. This allows operation at 1.23 bar of deuterium gas pressure in the gas cell region. Such a gas target system is free from the limitations of the windowed target but special attention has to be paid to the heat dissipation capability of the beam dump, due to the use of a thin target. The rotating seal concept is particularly suitable for use with accelerators such as radio-frequency quadrupole (RFQ) linacs that operate with a very high peak current at low duty cycle. The performance of both target systems was comprehensively characterized using the time-of-flight (TOF) technique. This demonstrated that very good quality mono-energetic fast neutron beams were produced with the slow neutron and gamma-ray component below 10% of the total target output

Fast Batch Production of High-Quality Graphene Films in a Sealed Thermal Molecular Movement System.

Science.gov (United States)

Xu, Jianbao; Hu, Junxiong; Li, Qi; Wang, Rubing; Li, Weiwei; Guo, Yufen; Zhu, Yongbo; Liu, Fengkui; Ullah, Zaka; Dong, Guocai; Zeng, Zhongming; Liu, Liwei

2017-07-01

Chemical vapor deposition (CVD) growth of high-quality graphene has emerged as the most promising technique in terms of its integrated manufacturing. However, there lacks a controllable growth method for producing high-quality and a large-quantity graphene films, simultaneously, at a fast growth rate, regardless of roll-to-roll (R2R) or batch-to-batch (B2B) methods. Here, a stationary-atmospheric-pressure CVD (SAPCVD) system based on thermal molecular movement, which enables fast B2B growth of continuous and uniform graphene films on tens of stacked Cu(111) foils, with a growth rate of 1.5 µm s -1 , is demonstrated. The monolayer graphene of batch production is found to nucleate from arrays of well-aligned domains, and the films possess few defects and exhibit high carrier mobility up to 6944 cm 2 V -1 s -1 at room temperature. The results indicate that the SAPCVD system combined with single-domain Cu(111) substrates makes it possible to realize fast batch-growth of high-quality graphene films, which opens up enormous opportunities to use this unique 2D material for industrial device applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of the fast electrons distribution produced in a high intensity laser target interaction

Energy Technology Data Exchange (ETDEWEB)

Westover, B. [Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California 92093 (United States); Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Chen, C. D.; Patel, P. K.; McLean, H. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Beg, F. N., E-mail: fbeg@ucsd.edu [Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California 92093 (United States)

2014-03-15

Experiments on the Titan laser (∼150 J, 0.7 ps, 2 × 10{sup 20} W cm{sup −2}) at the Lawrence Livermore National Laboratory were carried out in order to study the properties of fast electrons produced by high-intensity, short pulse laser interacting with matter under conditions relevant to Fast Ignition. Bremsstrahlung x-rays produced by these fast electrons were measured by a set of compact filter-stack based x-ray detectors placed at three angles with respect to the target. The measured bremsstrahlung signal allows a characterization of the fast electron beam spectrum, conversion efficiency of laser energy into fast electron kinetic energy and angular distribution. A Monte Carlo code Integrated Tiger Series was used to model the bremsstrahlung signal and infer a laser to fast electron conversion efficiency of 30%, an electron slope temperature of about 2.2 MeV, and a mean divergence angle of 39°. Simulations were also performed with the hybrid transport code ZUMA which includes fields in the target. In this case, a conversion efficiency of laser energy to fast electron energy of 34% and a slope temperature between 1.5 MeV and 4 MeV depending on the angle between the target normal direction and the measuring spectrometer are found. The observed temperature of the bremsstrahlung spectrum, and therefore the inferred electron spectrum are found to be angle dependent.

The Biological Effect of Fast Neutrons and High-Energy Protons

International Nuclear Information System (INIS)

Moskalev, Ju.I.; Petrovich, I.K.; Strel'cova, V.N.

1964-01-01

The paper gives the results of comparative experiments on the effects of fast neutrons and high-energy protons (500 MeV) on life expectancy, peripheral blood, incidence and rate of appearance of tumours in the rat as a function of administered dose and time of observation. The neutron experiment was performed on 573 and the proton experiment on 490 white rats. The animals irradiated with fast neutrons were given doses between 8.5 and 510 rad, and those irradiated with protons received doses between 28 and 1008 rad. The effective doses for the acute, sub-acute and chronic forms of sickness were established for fast neutrons and for protons. LD 50/30 for neutrons was 408 and for protons 600 rad, and the corresponding LD 50 / 120 values were 380 and 600 rad. The conditions governing rat mortality were analysed both in the early and the later stages of the experiment. It is shown that the average life expectancy of rats irradiated with fast neutrons does not depend on sex. The shape of the dose-effect curve for the various peripheral-blood indexes is strongly dependent not only on the radiosensitivity of the blood cells in question but also on the time of observation. It may change greatly in time for one and the same index. A considerable time after irradiation with either fast neutrons or protons, benign and malignant tumours appear in different tissues of the rats, including the haemopoeitic tissues, mammary glands, pituitary, uterus, ovaries, prostate gland, testicles, liver, kidneys, lungs, gastro-intestinal tract, subcutaneous tissue, lymph nodes, urinary bladder, etc. The over-all incidence of tumours and the number of cases of multi centred neoplasms in females are two to three times higher than in males. The minimum tumour dose for the mammary glands with neutron irradiation is apparently rather less than 42.5 rad. The maximum incidence of tumours of the pituitary is found after irradiation with a dose of 42.5 rad.- At this same dose leucosis and tumour of the

High current and high power superconducting rectifiers

International Nuclear Information System (INIS)

Kate, H.H.J. ten; Bunk, P.B.; Klundert, L.J.M. van de; Britton, R.B.

1981-01-01

Results on three experimental superconducting rectifiers are reported. Two of them are 1 kA low frequency flux pumps, one thermally and magnetically switched. The third is a low-current high-frequency magnetically switched rectifier which can use the mains directly. (author)

Electric Vehicles in Colorado: Anticipating Consumer Demand for Direct Current Fast Charging

Energy Technology Data Exchange (ETDEWEB)

Wood, Eric W. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rames, Clement L. [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2017-07-01

To support the State of Colorado in planning for growth in direct current fast charging (DCFC) for electric vehicles, the National Renewable Energy Laboratory (NREL) has partnered with the Regional Air Quality Council (RAQC) and the Colorado Department of Transportation (CDOT) to analyze a number of DCFC investment scenarios. NREL analyzed existing electric vehicle registration data from IHS Markit (IHS) to highlight early trends in the electric vehicle market, which were compared with sales forecasts predicting large growth in the Colorado electric vehicle market. Electric vehicle forecasts were then used to develop future DCFC scenarios to be evaluated in a simulation environment to estimate consumer benefits of the hypothetical DCFC networks in terms of increased driving range and electric vehicle miles traveled (eVMT). Simulated utilization of the hypothetical DCFC networks was analyzed for geographic trends, particularly for correlations with vehicle electric range. Finally, a subset of simulations is presented for consumers with potentially inconsistent access to charging at their home location and presumably greater reliance on public DCFC infrastructure.

Iodine laser of high efficiency and fast repetition rate

Energy Technology Data Exchange (ETDEWEB)

Hohla, K; Witte, K J

1976-07-01

The scaling laws of an iodine laser of high efficiency and fast repetition rate are reported. The laser is pumped with a new kind of low pressure Hg-UV-lamps which convert 32% of the electrical input in UV-light in the absorption band of the iodine laser and which can be fired up to 100 Hz. Details of a 10 kJ/1 nsec system as dimensions, energy density, repetition rate, flow velocity, gas composition and gas pressure and the overall efficiency are given which is expected to be about 2%.

libstable: Fast, Parallel, and High-Precision Computation of α-Stable Distributions in R, C/C++, and MATLAB

Directory of Open Access Journals (Sweden)

Javier Royuela-del-Val

2017-06-01

Full Text Available α-stable distributions are a family of well-known probability distributions. However, the lack of closed analytical expressions hinders their application. Currently, several tools have been developed to numerically evaluate their density and distribution functions or to estimate their parameters, but available solutions either do not reach sufficient precision on their evaluations or are excessively slow for practical purposes. Moreover, they do not take full advantage of the parallel processing capabilities of current multi-core machines. Other solutions work only on a subset of the α-stable parameter space. In this paper we present an R package and a C/C++ library with a MATLAB front-end that permit parallelized, fast and high precision evaluation of density, distribution and quantile functions, as well as random variable generation and parameter estimation of α-stable distributions in their whole parameter space. The described library can be easily integrated into third party developments.

Onset of Fast Magnetic Reconnection via Subcritical Bifurcation

Directory of Open Access Journals (Sweden)

ZHIBIN eGUO

2015-04-01

Full Text Available We report a phase transition model for the onset of fast magnetic reconnection. By investigating the joint dynamics of streaming instability(i.e., current driven ion acoustic in this paper and current gradient driven whistler wave {color{blue} {prior to the onset of fast reconnection}}, we show that the nonlinear evolution of current sheet(CS can be described by a Landau-Ginzburg equation. The phase transition from slow reconnection to fast reconnection occurs at a critical thickness, $Delta_csimeq frac{2}{sqrt{pi}}left|frac{v_{the}}{v_c}right|d_e$, where $v_{the}$ is electron thermal velocity and $v_c$ is the velocity threshold of the streaming instability. For current driven ion acoustic, $Delta_c$ is $leq10d_e$. If the thickness of the CS is narrower than $Delta_c$, the CS subcritically bifurcates into a rough state, which facilitates breakage of the CS, and consequently initiates fast reconnection.

Fast food (image)

Science.gov (United States)

Fast foods are quick, reasonably priced, and readily available alternatives to home cooking. While convenient and economical for a busy lifestyle, fast foods are typically high in calories, fat, saturated fat, ...

Fast neutron induced flux pinning in Tl-based high-Tc single crystals and thin films, highly textured tapes and melt-textured bulk 123-superconductors

International Nuclear Information System (INIS)

Brandstaetter, G.; Samadi Hosseinalli, G.; Kern, C.; Sauerzopf, F.M.; Schulz, G.W.; Straif, W.; Yang, X.; Weber, H.W.; Hu, Q.Y.

1999-01-01

Various compounds (TI-2223, TI-1223, TI-2212) as well as material forms (single crystals, thin films, ceramics, tapes) of TI-based high temperature superconductors were investigated by magnetic and transport techniques. TI-2223 has a very 'low lying' irreversibility line (H parallel e) and negligible critical current densities J c at 77 K. However, the irreversibility line shifts to higher fields and temperatures and J c is strongly enhanced, even at 77 K, after fast neutron irradiation. In contrast, the related TI-1223 compound has a much steeper irreversibility line (H parallel c) similar to that of Y-123. J c is significant up to 77 K, even in the unirradiated state, and can be largely improved by neutron irradiation. Transport measurements made on TI-1223 tapes still show much lower critical current densities. TI-2212 and Tl-2223 thin films have J c 's at 77 K, which are comparable to those of TI-1223 single crystals. Transport measurements on highly textured Bi-2223 tapes as well as flux profile measurements on Nd-123 bulk superconductors confirm the beneficial effects of neutron induced defects (collision cascades) for flux pinning. (author)

Monitoring the fast neutrons in a high flux: The case for {sup 242}Pu fission chambers

Energy Technology Data Exchange (ETDEWEB)

Filliatre, P.; Jammes, C.; Oriol, L.; Geslot, B. [Commissariat a l' Energie Atomique, DEN/SPEX/LDCI, Centre de Cadarache, F-13108 Saint-Paul-lez-Durance (France); Vermeeren, L. [SCK-CEN, Boeretang 200, B-2400 Mol (Belgium)

2009-07-01

Fission chambers are widely used for on-line monitoring of neutron fluxes in irradiation reactors. A selective measurement of a component of interest of the neutron flux is possible in principle thanks to a careful choice of the deposit material. However, measuring the fast component is challenging when the flux is high (up to 10{sup 15} n/cm{sup 2}/s) with a significant thermal component. The main problem is that the isotopic content of a material selected for its good response to fast neutrons evolves with irradiation, so that the material is more and more sensitive to thermal neutrons. Within the framework of the FNDS (Fast Neutron Detector System) project, we design tools that simulate the evolution of the isotopic composition and fission rate for several deposits under any given flux. In the case of a high flux with a significant thermal component, {sup 242}Pu is shown after a comprehensive study of all possibilities to be the best choice for measuring the fast component, as long as its purity is sufficient. If an estimate of the thermal flux is independently available, one can correct the signal for that component. This suggests a system of two detectors, one of which being used for such a correction. It is of very high interest when the detectors must be operated up to a high neutron fluence. (authors)

Measurements of fast ion spatial dynamics during magnetic activity in the RFP

Science.gov (United States)

Goetz, J. A.; Anderson, J. K.; Bonofiglo, P.; Kim, J.; McConnell, R.; Magee, R. M.

2017-10-01

Fast ions in the RFP are only weakly affected by a stochastic magnetic field and behave nearly classically in concentration too low to excite Alfvenic activity. At high fast ion concentration sourced by H-NBI in 300kA RFP discharges, a substantial drop in core-localized high pitch fast ions is observed during bursts of coupled EPM and IAE (magnetic island-induced Alfven eigenmode) activity (100-200kHz) through neutral particle analysis. Sourcing instead fast deuterium with NBI, the DD fusion products can measure the dynamics of the fast ion density profile. Both a collimated neutron detector and a new 3MeV fusion proton detector loaned by TriAlpha Energy measure the fast ion density profile with 5cm spatial resolution and 100 μs temporal resolution. In D-NBI, the bursting EPM is excited at slightly lower frequency and the IAE activity is nearly absent, likely due to an isotope effect and loss of wave-particle interaction. In these cases, neutral particle analysis shows little change in the core-localized high pitch fast ion content, and the fusion product profile indicates little change in the fast ion density profile, leaving unexplained the mechanism removing EPM drive. We measure a substantial redistribution of the fast ion profile due to strong lower-frequency ( 30kHz) MHD activity that accompanies the current profile relaxation in the RFP. Profile flattening is strongest in low bulk density discharges, which often occur with a total increase in global neutron flux from acceleration of the beam ions. Work supported by US DoE.

Conditions for substorm onset by the fast reconnection mechanism

Directory of Open Access Journals (Sweden)

M. Ugai

2008-12-01

Full Text Available The fast reconnection mechanism, involving slow shocks and Alfvénic fast plasma jets, is most responsible for the explosive conversion of magnetic energy associated with geomagnetic substorms and solar flares. In this paper, the spontaneous fast reconnection model is applied to well-known phenomena of substorms. When the east-west width of the tail current sheet becomes 3–4 times larger than its north-south thickness, the fast reconnection mechanism can fully be established, which may lead to substorm onset. The resulting Alfvénic jet can exactly explain, both qualitatively and quantitatively, the in-situ satellite observations of the traveling compression regions (TCRs associated with large-scale plasmoids propagating down the tail. Also, the earthward fast reconnection jet causes drastic magnetic field dipolarization, so that the sheet current ahead of the magnetic loop of closed field lines suddenly turns its direction toward the loop footpoint and a large-scale current wedge is formed according to the growth of field-aligned currents. It is demonstrated that an MHD generator arises ahead of the magnetic loop and drives the current wedge to distinctly enhance the current density in a pair of thin layers of the loop footpoint, giving rise to drastic heating in the form of two ribbons.

Preliminary design of the cooling system for a gas-cooled, high-fluence fast pulsed reactor (HFFPR)

International Nuclear Information System (INIS)

Monteith, H.C.

1978-10-01

The High-Fluence Fast Pulsed Reactor (HFFPR) is a research reactor concept currently being evaluated as a source for weapon effects experimentation and advanced reactor safety experiments. One of the designs under consideration is a gas-cooled design for testing large-scale weapon hardware or large bundles of full-length, fast reactor fuel pins. This report describes a conceptual cooling system design for such a reactor. The primary coolant would be helium and the secondary coolant would be water. The size of the helium-to-water heat exchanger and the water-to-water heat exchanger will be on the order of 0.9 metre (3 feet) in diameter and 3 metres (10 feet) in length. Analysis indicates that the entire cooling system will easily fit into the existing Sandia Engineering Reactor Facility (SERF) building. The alloy Incoloy 800H appears to be the best candidate for the tube material in the helium-to-water heat exchanger. Type 316 stainless steel has been recommended for the shell of this heat exchanger. Estimates place the cost of the helium-to-water heat exchanger at approximately $100,000, the water-to-water heat exchanger at approximately $25,000, and the helium pump at approximately $450,000. The overall cost of the cooling system will approach $2 million

Fast-ion Dα measurements of the fast-ion distribution (invited)

International Nuclear Information System (INIS)

Heidbrink, W. W.

2010-01-01

The fast-ion Dα (FIDA) diagnostic is an application of charge-exchange recombination spectroscopy. Fast ions that neutralize in an injected neutral beam emit Balmer-α light with a large Doppler shift. The spectral shift is exploited to distinguish the FIDA emission from other bright sources of Dα light. Background subtraction is the main technical challenge. A spectroscopic diagnostic typically achieves temporal, energy, and transverse spatial resolution of ∼1 ms, ∼10 keV, and ∼2 cm, respectively. Installations that use narrow-band filters achieve high spatial and temporal resolution at the expense of spectral information. For high temporal resolution, the bandpass-filtered light goes directly to a photomultiplier, allowing detection of ∼50 kHz oscillations in FIDA signal. For two-dimensional spatial profiles, the bandpass-filtered light goes to a charge-coupled device camera; detailed images of fast-ion redistribution at instabilities are obtained. Qualitative and quantitative models relate the measured FIDA signals to the fast-ion distribution function. The first quantitative comparisons between theory and experiment found excellent agreement in beam-heated magnetohydrodynamics (MHD)-quiescent plasmas. FIDA diagnostics are now in operation at magnetic-fusion facilities worldwide. They are used to study fast-ion acceleration by ion cyclotron heating, to detect fast-ion transport by MHD modes and microturbulence, and to study fast-ion driven instabilities.

Fast fission phenomena

International Nuclear Information System (INIS)

Gregoire, Christian.

1982-03-01

Experimental studies of fast fission phenomena are presented. The paper is divided into three parts. In the first part, problems associated with fast fission processes are examined in terms of interaction potentials and a dynamic model is presented in which highly elastic collisions, the formation of compound nuclei and fast fission appear naturally. In the second part, a description is given of the experimental methods employed, the observations made and the preliminary interpretation of measurements suggesting the occurence of fast fission processes. In the third part, our dynamic model is incorporated in a general theory of the dissipative processes studied. This theory enables fluctuations associated with collective variables to be calculated. It is applied to highly inelastic collisions, to fast fission and to the fission dynamics of compound nuclei (for which a schematic representation is given). It is with these calculations that the main results of the second part can be interpreted [fr

Calorie Underestimation When Buying High-Calorie Beverages in Fast-Food Contexts.

Science.gov (United States)

Franckle, Rebecca L; Block, Jason P; Roberto, Christina A

2016-07-01

We asked 1877 adults and 1178 adolescents visiting 89 fast-food restaurants in New England in 2010 and 2011 to estimate calories purchased. Calorie underestimation was greater among those purchasing a high-calorie beverage than among those who did not (adults: 324 ±698 vs 102 ±591 calories; adolescents: 360 ±602 vs 198 ±509 calories). This difference remained significant for adults but not adolescents after adjusting for total calories purchased. Purchasing high-calorie beverages may uniquely contribute to calorie underestimation among adults.

A high-current, high-voltage power supply with special output current waveform for APS injector synchrotron dipole magnets

International Nuclear Information System (INIS)

Fathizadeh, M.; Despe, O.D.; McGhee, D.G.; Mills, F.E.; Turner, L.R.

1991-01-01

This paper describes a high-voltage, high-current power supply for the injector synchrotron dipole magnets at APS. In order to reset the dipole magnets in each cycle two different current waveforms are suggested. The first current waveform consists of three sections, namely: dc-reset, linear ramp, and recovery sections where injection is done ''on the fly''. The second current waveform consists of six different sections, dc-reset, transition to injection level, injection flat level, parabolic, linear ramp and recovery sections. The effect of such waveforms on the beam is discussed and the power supply limitations to follow such waveforms are given. The power supply limitations are due to the power components and control loops. The reference for the current loop is generated by a DAC which is discussed

A performance model for the communication in fast multipole methods on high-performance computing platforms

KAUST Repository

Ibeid, Huda

2016-03-04

Exascale systems are predicted to have approximately 1 billion cores, assuming gigahertz cores. Limitations on affordable network topologies for distributed memory systems of such massive scale bring new challenges to the currently dominant parallel programing model. Currently, there are many efforts to evaluate the hardware and software bottlenecks of exascale designs. It is therefore of interest to model application performance and to understand what changes need to be made to ensure extrapolated scalability. The fast multipole method (FMM) was originally developed for accelerating N-body problems in astrophysics and molecular dynamics but has recently been extended to a wider range of problems. Its high arithmetic intensity combined with its linear complexity and asynchronous communication patterns make it a promising algorithm for exascale systems. In this paper, we discuss the challenges for FMM on current parallel computers and future exascale architectures, with a focus on internode communication. We focus on the communication part only; the efficiency of the computational kernels are beyond the scope of the present study. We develop a performance model that considers the communication patterns of the FMM and observe a good match between our model and the actual communication time on four high-performance computing (HPC) systems, when latency, bandwidth, network topology, and multicore penalties are all taken into account. To our knowledge, this is the first formal characterization of internode communication in FMM that validates the model against actual measurements of communication time. The ultimate communication model is predictive in an absolute sense; however, on complex systems, this objective is often out of reach or of a difficulty out of proportion to its benefit when there exists a simpler model that is inexpensive and sufficient to guide coding decisions leading to improved scaling. The current model provides such guidance.

ATLAS Fast Tracker Status and Tracking at High luminosity LHC

CERN Document Server

Ilic, Nikolina; The ATLAS collaboration

2018-01-01

The LHC’s increase in centre of mass energy and luminosity in 2015 makes controlling trigger rates with high efficiency challenging. The ATLAS Fast TracKer (FTK) is a hardware processor built to reconstruct tracks at a rate of up to 100 kHz and provide them to the high level trigger. The FTK reconstructs tracks by matching incoming detector hits with pre-defined track patterns stored in associative memory on custom ASICs. Inner detector hits are fit to these track patterns using modern FPGAs. This talk describes the electronics system used for the FTK’s massive parallelization. The installation, commissioning and running of the system is happening in 2016, and is detailed in this talk. Tracking at High luminosity LHC is also presented.

High Critical Current Coated Conductors

Energy Technology Data Exchange (ETDEWEB)

Paranthaman, M. P.; Selvamanickam, V. (SuperPower, Inc.)

2011-12-27

One of the important critical needs that came out of the DOE’s coated conductor workshop was to develop a high throughput and economic deposition process for YBCO. Metal-organic chemical vapor deposition (MOCVD) technique, the most critical steps in high technical micro fabrications, has been widely employed in semiconductor industry for various thin film growth. SuperPower has demonstrated that (Y,Gd)BCO films can be deposited rapid with world record performance. In addition to high critical current density with increased film thickness, flux pinning properties of REBCO films needs to be improved to meet the DOE requirements for various electric-power equipments. We have shown that doping with Zr can result in BZO nanocolumns, but at substantially reduced deposition rate. The primary purpose of this subtask is to develop high current density MOCVD-REBCO coated conductors based on the ion-beam assisted (IBAD)-MgO deposition process. Another purpose of this subtask is to investigate HTS conductor design optimization (maximize Je) with emphasis on stability and protection issues, and ac loss for REBCO coated conductors.

Studies of fast-ion transport induced by energetic particle modes using fast-particle diagnostics with high time resolution in CHS

International Nuclear Information System (INIS)

Isobe, M.; Toi, K.; Suzuki, C.; Nagaoka, K.; Matsushita, H.; Goto, K.

2006-01-01

The purpose of this work is to reveal the effects of the energetic particle mode (EPM) on fast-ion transport and consequent fast-ion loss in the Compact Helical System (CHS). For this purpose, fast particle diagnostics capable of following fast events originating from the EPM (f -5 Tesla at the magnetic probe position. The lost fast-ion probe (LIP) located at the outboard side of the torus indicates that bursting EPMs lead to periodically enhanced losses of co-going fast ions having smaller pitch angles in addition to losses of marginally co-passing fast ions. Coinciding with EPM bursts, the H- light detector viewing the peripheral region at the outboard side also shows large pulsed increases similar to that of the LIP whereas the detector viewing the peripheral region at the inboard side does not. This is also evidence that fast ions are expelled to the outboard side due to the EPM. The charge-exchange neutral particle analyzer indicates that only fast ions whose energy is close to the beam injection energy E b are strongly affected by EPM, suggesting in turn that observed EPMs are excited by fast ions having energy close to E b . (author)

Implications of rf current drive theory for next step steady-state tokamak design

International Nuclear Information System (INIS)

Schultz, J.H.

1985-06-01

Two missions have been identified for a next-step tokamak experiment in the United States. The more ambitious Mission II device would be a superconducting tokamak, capable of doing long-pulse ignition demonstrations, and hopefully capable of also being able to achieve steady-state burn. A few interesting lines of approach have been identified, using a combination of logical design criteria and parametric system scans [SC85]. These include: (1) TIBER: A point-design suggested by Lawrence Livermore, that proposes a machine with the capability of demonstrating ignition, high beta (10%) and high Q (=10), using high frequency, fast-wave current drive. The TIBER topology uses moderate aspect ratio and high triangularity to achieve high beta. (2) JET Scale-up. (3) Magic5: It is argued here that an aspect ratio of 5 is a magic number for a good steady-state current drive experiment. A moderately-sized machine that achieves ignition and is capable of high Q, using either fast wave or slow wave current drive is described. (4) ET-II: The concept of a highly elongated tokamak (ET) was first proposed as a low-cost approach to Mission I, because of the possibility of achieving ohmic ignition with low-stress copper magnets. We propose that its best application is really for commercial tokamaks, using fast-wave current drive, and suggest a Mission II experiment that would be prototypical of such a reactor

Fast Magnetic Reconnection: Bridging Laboratory and Space Plasma Physics

Energy Technology Data Exchange (ETDEWEB)

Bhattacharjee, Amitava [University New Hampshire- Durham

2012-02-16

Recent developments in experimental and theoretical studies of magnetic reconnection hold promise for providing solutions to outstanding problems in laboratory and space plasma physics. Examples include sawtooth crashes in tokamaks, substorms in the Earth’s Magnetosphere, eruptive solar flares, and more recently, fast reconnection in laser-produced high energy density plasmas. In each of these examples, a common and long-standing challenge has been to explain why fast reconnection proceeds rapidly from a relatively quiescent state. In this talk, we demonstrate the advantages of viewing these problems and their solutions from a common perspective. We focus on some recent, surprising discoveries regarding the role of secondary plasmoid instabilities of thin current sheets. Nonlinearly, these instabilities lead to fast reconnection rates that are very weakly dependent on the Lundquist number of the plasma.

Ultra-fast low concentration detection of Candida pathogens utilizing high resolution micropore chips.

Science.gov (United States)

Mulero, Rafael; Lee, Dong Heun; Kutzler, Michele A; Jacobson, Jeffrey M; Kim, Min Jun

2009-01-01

Although Candida species are the fourth most common cause of nosocomial blood stream infections in the United States, early diagnostic tools for invasive candidemia are lacking. Due to an increasing rate of candidemia, a new screening system is needed to detect the Candida species in a timely manner. Here we describe a novel method of detection using a solid-state micro-scale pore similar to the operational principles of a Coulter counter. With a steady electrolyte current flowing through the pore, measurements are taken of changes in the current corresponding to the shape of individual yeasts as they translocate or travel through the pore. The direct ultra-fast low concentration electrical addressing of C. albicans has established criteria for distinguishing individual yeast based on their structural properties, which may reduce the currently used methods' complexity for both identification and quantification capabilities in mixed blood samples.

Ultra-Fast Low Concentration Detection of Candida Pathogens Utilizing High Resolution Micropore Chips

Directory of Open Access Journals (Sweden)

2009-03-01

Full Text Available Although Candida species are the fourth most common cause of nosocomial blood stream infections in the United States, early diagnostic tools for invasive candidemia are lacking. Due to an increasing rate of candidemia, a new screening system is needed to detect the Candida species in a timely manner. Here we describe a novel method of detection using a solid-state micro-scale pore similar to the operational principles of a Coulter counter. With a steady electrolyte current flowing through the pore, measurements are taken of changes in the current corresponding to the shape of individual yeasts as they translocate or travel through the pore. The direct ultra-fast low concentration electrical addressing of C. albicans has established criteria for distinguishing individual yeast based on their structural properties, which may reduce the currently used methods’ complexity for both identification and quantification capabilities in mixed blood samples

A new high performance current transducer

International Nuclear Information System (INIS)

Tang Lijun; Lu Songlin; Li Deming

2003-01-01

A DC-100 kHz current transducer is developed using a new technique on zero-flux detecting principle. It was shown that the new current transducer is of high performance, its magnetic core need not be selected very stringently, and it is easy to manufacture

Non-inductive current drive experiments on DIII-D, and future plans

International Nuclear Information System (INIS)

Prater, R.; Austin, M.; Baity, F.W.; Callis, R.W.; Chiu, S.C.; DeGrassie, J.S.; Freeman, R.L.; Forest, C.B.; Goulding, R.H.; Harvey, R.W.; Hoffman, D.J.; Ikezi, H.; Lohr, J.; James, R.A.; Kupfer, K.; Lin-Liu, Y.R.; Luce, T.C.; Moeller, C.P.; Petty, C.C.; Pinsker, R.I.; Porkolab, M.; Squire, J.; Trukhin, V.

1995-01-01

Experiments on DIII-D (and other tokamaks) have shown that improved performance can follow from optimization of the current density profile. Increased confinement of energy and a higher limit on β have both been found in discharges in which the current density profile is modified through transient means, such as ramping of current or elongation. Peaking of the current distribution to obtain discharges with high internal inductance l i has been found to be beneficial. Alternatively, discharges with broader profiles, as in the VH mode or with high β poloidal, have shown improved performance. Non-inductive current drive is a means to access these modes of improved confinement on a steady state basis. Accordingly, experiments on non-inductive current drive are underway on the DIII-D tokamak using fast waves and electron cyclotron waves. Recent experiments on fast wave current drive have demonstrated the ability to drive up to 180kA of non-inductive current using 1.5MW of power at 60MHz, including the contribution from 1MW of ECCD and the bootstrap current. Higher power r.f. current drive systems are needed to affect strongly the current profile on DIII-D. An upgrade to the fast wave current drive system is underway to increase the total power to 6MW, using two additional antennas and two new 30-120MHz transmitters. Additionally, a 1MW prototype ECH system at 110GHz is being developed (with eventual upgrade to 10MW). With these systems, non-inductive current drive at the 1MA level will be available for experiments on profile control in DIII-D. ((orig.))

The Fast-Casual Conundrum: Fast-Casual Restaurant Entrées Are Higher in Calories than Fast Food.

Science.gov (United States)

Schoffman, Danielle E; Davidson, Charis R; Hales, Sarah B; Crimarco, Anthony E; Dahl, Alicia A; Turner-McGrievy, Gabrielle M

2016-10-01

Frequently eating fast food has been associated with consuming a diet high in calories, and there is a public perception that fast-casual restaurants (eg, Chipotle) are healthier than traditional fast food (eg, McDonald's). However, research has not examined whether fast-food entrées and fast-casual entrées differ in calorie content. The purpose of this study was to determine whether the caloric content of entrées at fast-food restaurants differed from that found at fast-casual restaurants. This study was a cross-sectional analysis of secondary data. Calorie information from 2014 for lunch and dinner entrées for fast-food and fast-casual restaurants was downloaded from the MenuStat database. Mean calories per entrée between fast-food restaurants and fast-casual restaurants and the proportion of restaurant entrées that fell into different calorie ranges were assessed. A t test was conducted to test the hypothesis that there was no difference between the average calories per entrée at fast-food and fast-casual restaurants. To examine the difference in distribution of entrées in different calorie ranges between fast-food and fast-casual restaurants, χ(2) tests were used. There were 34 fast-food and 28 fast-casual restaurants included in the analysis (n=3,193 entrées). Fast-casual entrées had significantly more calories per entrée (760±301 kcal) than fast-food entrées (561±268; Prestaurants to determine whether the energy content or nutrient density of full meals (ie, entrées with sides and drinks) differs between fast-casual restaurants and fast-food restaurants. Calorie-conscious consumers should consider the calorie content of entrée items before purchase, regardless of restaurant type. Copyright © 2016 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

The Association between Socio-Demographic Charactristics and Fast Food Consumption withinHigh School Students in Isfahan, Iran

OpenAIRE

Parastoo Yarmohammadi; Gholam Reza Sharifirad; Leila Azadbakht; Parisa Yarmohammadi; Zohreh Rahaei; Vali Bahrevar; Zahra Khajeh

2015-01-01

Abstract Introduction: Fast food consumption has greatly increased with in adolescents in recent years, which is linked with weight gain, poor dietary indexes and insulin resistance. Hence, the purpose of this study was to examine the association between demographic characteristics and fast food consumption with in high school students. Materials & Methods: In this descriptive-analytic study, a sample of 521 high school students  aged 15-18 years were examined in Isfahan city, who wer...

Metabolic Profiles in Children During Fasting

NARCIS (Netherlands)

van Veen, Merel R.; van Hasselt, Peter M.; de Sain-van der Velden, Monique G. M.; Verhoeven, Nanda; Hofstede, Floris C.; de Koning, Tom J.; Visser, Gepke

BACKGROUND: Hypoglycemia is one of the most common metabolic derangements in childhood. To establish the cause of hypoglycemia, fasting tolerance tests can be used. Currently available reference values for fasting tolerance tests have limitations in their use in daily practice. OBJECTIVE: The aim of

High power fast ramping power supplies

Energy Technology Data Exchange (ETDEWEB)

Marneris,I.; Bajon, E.; Bonati, R.; Sandberg, J.; Roser, T.; Tsoupas, N.

2009-05-04

Hundred megawatt level fast ramping power converters to drive proton and heavy ion machines are under research and development at accelerator facilities in the world. This is a leading edge technology. There are several topologies to achieve this power level. Their advantages and related issues will be discussed.

FastMag: Fast micromagnetic simulator for complex magnetic structures (invited)

Science.gov (United States)

Chang, R.; Li, S.; Lubarda, M. V.; Livshitz, B.; Lomakin, V.

2011-04-01

A fast micromagnetic simulator (FastMag) for general problems is presented. FastMag solves the Landau-Lifshitz-Gilbert equation and can handle multiscale problems with a high computational efficiency. The simulator derives its high performance from efficient methods for evaluating the effective field and from implementations on massively parallel graphics processing unit (GPU) architectures. FastMag discretizes the computational domain into tetrahedral elements and therefore is highly flexible for general problems. The magnetostatic field is computed via the superposition principle for both volume and surface parts of the computational domain. This is accomplished by implementing efficient quadrature rules and analytical integration for overlapping elements in which the integral kernel is singular. Thus, discretized superposition integrals are computed using a nonuniform grid interpolation method, which evaluates the field from N sources at N collocated observers in O(N) operations. This approach allows handling objects of arbitrary shape, allows easily calculating of the field outside the magnetized domains, does not require solving a linear system of equations, and requires little memory. FastMag is implemented on GPUs with ?> GPU-central processing unit speed-ups of 2 orders of magnitude. Simulations are shown of a large array of magnetic dots and a recording head fully discretized down to the exchange length, with over a hundred million tetrahedral elements on an inexpensive desktop computer.

DMPDS: A Fast Motion Estimation Algorithm Targeting High Resolution Videos and Its FPGA Implementation

Directory of Open Access Journals (Sweden)

Gustavo Sanchez

2012-01-01

Full Text Available This paper presents a new fast motion estimation (ME algorithm targeting high resolution digital videos and its efficient hardware architecture design. The new Dynamic Multipoint Diamond Search (DMPDS algorithm is a fast algorithm which increases the ME quality when compared with other fast ME algorithms. The DMPDS achieves a better digital video quality reducing the occurrence of local minima falls, especially in high definition videos. The quality results show that the DMPDS is able to reach an average PSNR gain of 1.85 dB when compared with the well-known Diamond Search (DS algorithm. When compared to the optimum results generated by the Full Search (FS algorithm the DMPDS shows a lose of only 1.03 dB in the PSNR. On the other hand, the DMPDS reached a complexity reduction higher than 45 times when compared to FS. The quality gains related to DS caused an expected increase in the DMPDS complexity which uses 6.4-times more calculations than DS. The DMPDS architecture was designed focused on high performance and low cost, targeting to process Quad Full High Definition (QFHD videos in real time (30 frames per second. The architecture was described in VHDL and synthesized to Altera Stratix 4 and Xilinx Virtex 5 FPGAs. The synthesis results show that the architecture is able to achieve processing rates higher than 53 QFHD fps, reaching the real-time requirements. The DMPDS architecture achieved the highest processing rate when compared to related works in the literature. This high processing rate was obtained designing an architecture with a high operation frequency and low numbers of cycles necessary to process each block.

Quench properties of high current superconductors

Energy Technology Data Exchange (ETDEWEB)

Garber, M; Sampson, W B

1980-01-01

A technique has been developed which allows the simultaneous determination of most of the important parameters of a high current superconductor. The critical current, propagation velocity, normal state resistivity, magnetoresistance, and enthalpy are determined as a function of current and applied field. The measurements are made on non-inductive samples which simulate conditions in full scale magnets. For wide, braided conductors the propagation velocity was found to vary approximately quadratically with current in the 2 to 5 kA region. A number of conductors have been tested including some Nb/sub 3/Sn braids which have critical currents in excess of 10 kA at 5 T, 4.2 K.

Fast Faraday Cup With High Bandwidth

Science.gov (United States)

Deibele, Craig E [Knoxville, TN

2006-03-14

A circuit card stripline Fast Faraday cup quantitatively measures the picosecond time structure of a charged particle beam. The stripline configuration maintains signal integrity, and stitching of the stripline increases the bandwidth. A calibration procedure ensures the measurement of the absolute charge and time structure of the charged particle beam.

Fast engineering optimization: A novel highly effective control parameterization approach for industrial dynamic processes.

Science.gov (United States)

Liu, Ping; Li, Guodong; Liu, Xinggao

2015-09-01

Control vector parameterization (CVP) is an important approach of the engineering optimization for the industrial dynamic processes. However, its major defect, the low optimization efficiency caused by calculating the relevant differential equations in the generated nonlinear programming (NLP) problem repeatedly, limits its wide application in the engineering optimization for the industrial dynamic processes. A novel highly effective control parameterization approach, fast-CVP, is first proposed to improve the optimization efficiency for industrial dynamic processes, where the costate gradient formulae is employed and a fast approximate scheme is presented to solve the differential equations in dynamic process simulation. Three well-known engineering optimization benchmark problems of the industrial dynamic processes are demonstrated as illustration. The research results show that the proposed fast approach achieves a fine performance that at least 90% of the computation time can be saved in contrast to the traditional CVP method, which reveals the effectiveness of the proposed fast engineering optimization approach for the industrial dynamic processes. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

High-current beam transport in electrostatic accelerator tubes

International Nuclear Information System (INIS)

Ramian, G.; Elais, L.

1987-01-01

The UCSB Free Electron Laser (FEL) has successfully demonstrated the use of a commercial 6 megavolt electrostatic accelerator as a high current beam source in a recirculating configuration. The accelerator, manufactured by National Electrostatics Corp. (NEC), Middleton WI, uses two standard high gradient accelerator tubes. Suppression of ion multiplication was accomplished by NEC with apertures and a shaped electrostatic field. This field shaping has fortuitously provided a periodically reversing radial field component with sufficient focusing strength to transport electron beams of up to 3 Amps current. Present two-stage FEL work requires a 20 Amp beam and proposed very high voltage FEL designs require currents as high as 100 Amps. A plan to permit transport of such high current beams by the addition of solenoidal focussing elements is described

LAMPF first-fault identifier for fast transient faults

International Nuclear Information System (INIS)

Swanson, A.R.; Hill, R.E.

1979-01-01

The LAMPF accelerator is presently producing 800-MeV proton beams at 0.5 mA average current. Machine protection for such a high-intensity accelerator requires a fast shutdown mechanism, which can turn off the beam within a few microseconds of the occurrence of a machine fault. The resulting beam unloading transients cause the rf systems to exceed control loop tolerances and consequently generate multiple fault indications for identification by the control computer. The problem is to isolate the primary fault or cause of beam shutdown while disregarding as many as 50 secondary fault indications that occur as a result of beam shutdown. The LAMPF First-Fault Identifier (FFI) for fast transient faults is operational and has proven capable of first-fault identification. The FFI design utilized features of the Fast Protection System that were previously implemented for beam chopping and rf power conservation. No software changes were required

Recriticality, a Key Phenomenon to Investigate in Core Disruptive Accident Scenarios of Current and Future Fast Reactor Designs

International Nuclear Information System (INIS)

Maschek, W.; Rineiski, A.; Flad, M.; Kriventsev, V.; Gabrielli, F.; Morita, K.

2012-01-01

Final comments and conclusions: • Modern plants, should have performed better under Fukushima type event. • In future fast reactor systems significantly higher active and passive safety features are installed, which should cope with events like Fukushima. • One important lesson: put a focus on rare initiators, accident routes and consequences that are neither expected nor have been observed, events that are categorized under ‘black swans’. • Importance of severe accident research demonstrated - both analytically and experimentally for assessing and interpreting accident scenarios and developments. Precondition for developing preventive & mitigative safety measures. Passive safety measures are in the focus of advanced design options and must work under conditions of multiple loads and aggravating events. • Fast reactor systems behavior as the SFR under severe accident conditions: – In fast spectrum systems as the SFR the core is not in its neutronically most reactive configuration and SFRs may be loaded with MAs for waste management; – Recriticalities have a high probability because of the higher enrichment levels; – Short time scales have to be envisioned for core melt-down; – Decay heat levels might be significantly higher, if MA bearing fuel is involved. • Improve design by measures for prevention and/or mitigation of recriticalities; – High reliability of simulations required for proof; • Assessment of fuel relocated on peripheral structures; • Preventive/mitigating measures should not replace containment measures

Design and realization of a fast digital system for the protection of a linear accelerator

International Nuclear Information System (INIS)

Hamdi, A.

2004-07-01

The new generation of light sources based on SASE Free-Electron-Lasers driven by LINACs operate with electron beams with high beam currents and duty cycles. This is especially true for the superconducting machines like TTF 2 and the X-RAY FEL, under construction or planning at DESY. Elaborate fast protections systems are required not only to protect the machine from electron beams hitting and destroying the vacuum chamber, but also to prevent the machine from running at high loss levels, dangerous for components like the FEL undulator. This document presents the different protection systems currently under construction for TTF 2. The very fast systems, based on transmission measurements and distributed loss detection monitors, are described in detail. This description includes the fast electronics to collect and to transmit the different interlock and status signals: analog to digital converters, DSP and FPGA, interfaces, toroid protection system (TPS) card. The implementation and validation (simulation and tests) of the TPS card at DESY is presented

High-current power supply for accelerator magnets

International Nuclear Information System (INIS)

Bourkland, K.R.; Winje, R.A.

1978-01-01

A power supply for controlling the current to accelerator magnets produces a high current at a precisely controlled time rate of change by varying the resonant frequency of an RLC circuit that includes the magnet and applying the current to the magnet during a predetermined portion of the waveform of an oscillation. The current is kept from going negative despite the reverse-current characteristics of thyristors by a quenching circuit

Current drive and sustain experiments with the bootstrap current in JT-60

International Nuclear Information System (INIS)

Kikuchi, Mitsuru; Azumi, Masafumi; Tani, Keiji; Tsuji, Shunji; Kubo, Hirotaka

1989-11-01

The current drive and sustain experiments with the neoclassical bootstrap current are performed in the JT-60 tokamak. It is shown that up to 80% of total plasma current is driven by the bootstrap current in extremely high β p regime (β p = 3.2) and the current drive product I p (bootstrap) n-bar e R p up to 4.4 x 10 19 MAm -2 has been attained with the bootstrap current. The experimental resistive loop voltages are compared with the calculations using the neoclassical resistivity with and without the bootstrap current and the Spitzer resistivity for a wide range of the plasma current (I p = 0.5 -2 MA) and the poloidal beta (β p = 0.1 - 3.2). The calculated resistive loop voltage is consistent with the neoclassical prediction including the bootstrap current. Current sustain with the bootstrap current is tested by terminating the I p feedback control during the high power neutral beam heating. An enhancement of the L/R decay time than those expected from the plasma resistivity with measured T e and Zeff has been confirmed experimentally supporting the large non-inductive current in the plasma and is consistent with the neoclassical prediction. A new technique to calculate the bootstrap current in multi-collisionality regime for finite aspect ratio tokamak has bee developed. The neoclassical bootstrap current is calculated directly through the force balance equations between viscous and friction forces according to the Hirshman-Sigmar theory. The bootstrap current driven by the fast ion component is also included. Ballooning stability of the high β p plasma are analyzed using the current profiles including the bootstrap current. The plasma pressure is close to the ballooning limit in high β p discharges. (author)

Designing single phase Current-Programmed-Controlled rectifiers by harmonic currents

DEFF Research Database (Denmark)

Andersen, Gert Karmisholt; Blaabjerg, Frede

2002-01-01

The grid current harmonics of a Current-Programmed-Controlled (CPC) pfc rectifier strongly depends on the choice of switching frequency and switching inductance. This paper describes a new simple and vert fast method to calculate the grid current of a CPC controlled pfc converter. The method...

Nanoarchitectured current collector for high rate capability of polyaniline based supercapacitor electrode

International Nuclear Information System (INIS)

Sumboja, Afriyanti; Wang Xu; Yan Jian; Lee, Pooi See

2012-01-01

Highlights: ► Preparation of organic/inorganic coaxial nanowires. ► Modifying current collector to improve both capacitance and rate capability simultaneously. ► Improvement in the charge transport process resulted in the superior rate capability. - Abstract: Indium tin oxide (ITO) nanowires array was used as current collector and building block for polyaniline based supercapacitor. Thin polyaniline coating was deposited on the nanowires and resulted in the formation of polyaniline ITO coaxial nanowires. This hybrid heterostructure design improved the specific capacitance, rate capability, and cycling stability of the supercapacitor electrode. Good conductivity harnessed by these directly grown ITO nanowires is useful to improve the charge transport during the charge discharge processes which were confirmed by the electrochemical impedance spectroscopy measurement. Electrochemical test in 1 M H 2 SO 4 at 4 A g −1 delivered specific capacitance as high as 738 F g −1 . In addition, sub-micron size of the intercoaxial nanowires spacing ensures the fast penetration of electrolyte ions which resulted in the superior rate capability (98% capacitance retention when applied current was varied from 4 to 25 A g −1 ). The capacitance retention is significantly higher as compared to other polyaniline composite electrodes and it is one of the best reported performances to date for polyaniline based supercapacitor electrodes. This work illustrates a promising platform that can be adopted for other redox nanocomposite materials while reaping the benefit as low cost and binder free electrode material for supercapacitor application.

Fast and efficient STT switching in MTJ using additional transient pulse current

Science.gov (United States)

Pathak, Sachin; Cha, Jongin; Jo, Kangwook; Yoon, Hongil; Hong, Jongill

2017-06-01

We propose a profile of write pulse current-density to switch magnetization in a perpendicular magnetic tunnel junction to reduce switching time and write energy as well. Our simulated results show that an overshoot transient pulse current-density (current spike) imposed to conventional rectangular-shaped pulse current-density (main pulse) significantly improves switching speed that yields the reduction in write energy accordingly. For example, we could dramatically reduce the switching time by 80% and thereby reduce the write energy over 9% in comparison to the switching without current spike. The current spike affects the spin dynamics of the free layer and reduces the switching time mainly due to spin torque induced. On the other hand, the large Oersted field induced causes changes in spin texture. We believe our proposed write scheme can make a breakthrough in magnetic random access memory technology seeking both high speed operation and low energy consumption.

Fast pressure measurements for the TMX-U fusion experiment

International Nuclear Information System (INIS)

Hunt, A.L.; Coffield, F.E.; Pickles, W.L.

1982-01-01

The pressure on the boundary of the Lawrence Livermore National Laboratory's (LLNL) tandem mirror (TMX-U) plasma experiment is difficult to trace for several reasons: (1) the TMX-U boundary is in the high vacuum range (10 -5 to 10 -6 Pa) and requires an ionization gauge; (2) the boundary includes high-energy neutral particles and radiation, so the gauge must be optically baffled from the plasma; (3) the gauge must be shielded from the magnetic flux density of 0.03 T; (4) maximum conductance to the gauge must be preserved so that the time response remains about 1 ms; (5) a fast electrical circuit is required to measure the small ion-current changes at a rate consistent with the geometrical and experimental time constant of 1 ms. We have developed solutions to these limitations, including fast ionization gauge (FIG) circuitry for the remote gauge operation and the CAMAC system for recording the pressure-time history in the TMX-U computer data base. We also give some examples of actual fast pressure histories during plasma operation

On establishing constitutive equations for use in design of high-temperature fast-reactor structures

International Nuclear Information System (INIS)

Pugh, C.E.

1978-01-01

The presentation describes the approach being used to establish constitutive equations for wide use in the design of fast breeder reactor (FBR) components in the US. The approach combines exploratory experiments, constitutive model studies, studies of computational techniques, and tests of simple structural configurations. Short-time (elastic-plastic) behavior, long-time (creep) behavior, and their interactions are considered, and some of the background to equations now identified for use in current FBR design applications involving three structural alloys is discussed. Comments are also given on current efforts aimed at identifying improved constitutive equations for these alloys and on properties data required for design applications. References are cited which have addressed the status of the process at various times. (Auth.)

Physiology of Ramadan fasting

OpenAIRE

Shokoufeh Bonakdaran

2016-01-01

Considering the emphasis of Islam on the importance of fasting, Muslims attempt to fast from dawn until sunset during the holy month of Ramadan. Fasting is associated with several benefits for normal and healthy individuals. However, it could pose high risks to the health of diabetic patients due to certain physiological changes. This study aimed to compare the physiological changes associated with fasting in healthy individuals and diabetic patients during Ramadan. Furthermore, we reviewed t...

Test data on electrical contacts at high surface velocities and high current densities for homopolar generators

International Nuclear Information System (INIS)

Brennan, M.; Tolk, K.M.; Weldon, W.F.; Rylander, H.G.; Woodson, H.H.

1977-01-01

Test data is presented for one grade of copper graphite brush material, Morganite CMlS, over a wide range of surface velocities, atmospheres, and current densities that are expected for fast discharge (<100 ms) homopolar generators. The brushes were run on a copper coated 7075-T6 aluminum disk at surface speeds up to 277 m/sec. One electroplated copper and three flame sprayed copper coatings were used during the tests. Significant differences in contact voltage drops and surface mechanical properties of the copper coatings were observed

Obese mice on a high-fat alternate-day fasting regimen lose weight and improve glucose tolerance.

Science.gov (United States)

Joslin, P M N; Bell, R K; Swoap, S J

2017-10-01

Alternate-day fasting (ADF) causes body weight (BW) loss in humans and rodents. However, it is not clear that ADF while maintaining a high-fat (HF) diet results in weight loss and the accompanying improvement in control of circulating glucose. We tested the hypotheses that a high-fat ADF protocol in obese mice would result in (i) BW loss, (ii) improved glucose control, (iii) fluctuating phenotypes on 'fasted' days when compared to 'fed' days and (iv) induction of torpor on 'fasted days'. We evaluated the physiological effects of ADF in diet-induced obese mice for BW, heart rate (HR), body temperature (T b ), glucose tolerance, insulin responsiveness, blood parameters (leptin, insulin, free fatty acids) and hepatic gene expression. Diet-induced obese male C57BL/6J mice lost one-third of their pre-diet BW while on an ADF diet for 10 weeks consisting of HF food. The ADF protocol improved glucose tolerance and insulin sensitivity, although mice on a fast day were less glucose tolerant than the same mice on a fed day. ADF mice on a fast day had low circulating insulin, but had an enhanced response to an insulin-assisted glucose tolerance test, suggesting the impaired glucose tolerance may be a result of insufficient insulin production. On fed days, ADF mice were the warmest, had a high HR and displayed hepatic gene expression and circulating leptin that closely mimicked that of mice fed an ad lib HF diet. ADF mice never entered torpor as assessed by HR and T b . However, on fast days, they were the coolest, had the slowest HR, and displayed hepatic gene expression and circulating leptin that closely mimicked that of Chow-Fed mice. Collectively, the ADF regimen with a HF diet in obese mice results in weight loss, improved blood glucose control, and daily fluctuations in selected physiological and biochemical parameters in the mouse. Journal of Animal Physiology and Animal Nutrition © 2016 Blackwell Verlag GmbH.

High current vacuum closing switch

International Nuclear Information System (INIS)

Dolgachev, G.I.; Maslennikov, D.D.; Romanov, A.S.; Ushakov, A.G.

2005-01-01

The paper proposes a powerful pulsed closing vacuum switch for high current commutation consisting of series of the vacuum diodes with near 1 mm gaps having closing time determined by the gaps shortening with the near-electrode plasmas [ru

Pulse shape discrimination based on fast signals from silicon photomultipliers

Science.gov (United States)

Yu, Junhao; Wei, Zhiyong; Fang, Meihua; Zhang, Zixia; Cheng, Can; Wang, Yi; Su, Huiwen; Ran, Youquan; Zhu, Qingwei; Zhang, He; Duan, Kai; Chen, Ming; Liu, Meng

2018-06-01

Recent developments in organic plastic scintillators capable of pulse shape discrimination (PSD) enable a breakthrough in discrimination between neutrons and gammas. Plastic scintillator detectors coupled with silicon photomultipliers (SiPMs) offer many advantages, such as lower power consumption, smaller volume, and especially insensitivity to magnetic fields, compared with conventional photomultiplier tubes (PMTs). A SensL SiPM has two outputs: a standard output and a fast output. It is known that the charge injected into the fast output electrode is typically approximately 2% of the total charge generated during the avalanche, whereas the charge injected into the standard output electrode is nearly 98% of the total. Fast signals from SiPMs exhibit better performance in terms of timing and time-correlated measurements compared with standard signals. The pulse duration of a standard signal is on the order of hundreds of nanoseconds, whereas the pulse duration of the main monopole waveform of a fast signal is a few tens of nanoseconds. Fast signals are traditionally thought to be suitable for photon counting at very high speeds but unsuitable for PSD due to the partial charge collection. Meanwhile, the standard outputs of SiPMs coupled with discriminating scintillators have yielded nice PSD performances, but there have been no reports on PSD using fast signals. Our analysis shows that fast signals can also provide discrimination if the rate of charge injection into the fast output electrode is fixed for each event, even though only a portion of the charge is collected. In this work, we achieved successful PSD using fast signals; meanwhile, using a coincidence timing window of less 3 nanoseconds between the readouts from both ends of the detector reduced the influence of the high SiPM dark current. We experimentally achieved good timing performance and PSD capability simultaneously.

High current density ion beam measurement techniques

International Nuclear Information System (INIS)

Ko, W.C.; Sawatzky, E.

1976-01-01

High ion beam current measurements are difficult due to the presence of the secondary particles and beam neutralization. For long Faraday cages, true current can be obtained only by negative bias on the target and by summing the cage wall and target currents; otherwise, the beam will be greatly distorted. For short Faraday cages, a combination of small magnetic field and the negative target bias results in correct beam current. Either component alone does not give true current

On transition from diffuse mode to the constricted one with high-current cathode spot in overvoltage open discharge in D2

Science.gov (United States)

Akishev, Yu S.; Karalnik, V. B.; Medvedev, M. A.; Petryakov, A. V.; Trushkin, N. I.; Shafikov, A. G.

2017-11-01

So called “open discharges” in a narrow gap between the solid cathode and grid anode are widely used for generation of the pulsed high-current electron beams with energy up to 100 keV. The need to get high-energy e-beams leads to the necessity in using of strong overvoltage of the short gas gap with the reduced electric field of the order of 105 Td or higher. The discharge under strong overvoltage is unstable and tends to transit into high-current regime with low voltage. In the case of the open discharge in D2 at low pressure (about 0.5-2 Torr) and powered by stepwise voltage with amplitude up to 25 kV we revealed that this discharge exhibits two diffuse regimes which follow one by one and finally transits into the constricted mode with formation of high-current spots on the cathode. The physical properties of these gas discharge regimes have been explored in detail with the usage of the fast multi-frame camera synchronized with the current and voltage of discharge. Our findings promote more insight into physics of the overvoltage open discharge generating the e-beams with energy up to 25 keV.

Variational full wave calculation of fast wave current drive in DIII-D using the ALCYON code

International Nuclear Information System (INIS)

Becoulet, A.; Moreau, D.

1992-04-01

Initial fast wave current drive simulations performed with the ALCYON code for the 60 MHz DIII-D experiment are presented. Two typical shots of the 1991 summer campaign were selected with magnetic field intensities of 1 and 2 teslas respectively. The results for the wave electromagnetic field in the plasma chamber are displayed. They exhibit a strong enrichment of the poloidal mode number m-spectrum which leads to the upshift of the parallel wavenumber, κ perpendicular, and to the wave absorption. The m-spectrum is bounded when the local poloidal wavenumber reaches the Alfven wavenumber and the κ perpendicular upshifts do not destroy the wave directionality. Linear estimations of the driven current are made. The current density profiles are found to be peaked and we find that about 88 kA can be driven in the 1 tesla/1.7 keV phase with 1.7 MW coupled to the electrons. In the 2 tesla/3.4 keV case, 47 kA are driven with a total power of 1.5 MW, 44% of which are absorbed on the hydrogen minority, through the second harmonic ion cyclotron resonance. The global efficiency is then 0.18 x 10 19 A m -2 W -1 if one considers only the effective power going to the electrons

Fast generation of dendritic cells

DEFF Research Database (Denmark)

Kvistborg, P; Bøgh, Marie; Pedersen, A W

2009-01-01

we have developed fast DC protocol by comparing two different fast DC protocols with SDDC. DC were evaluated by FACS analysis, and the optimal profile was considered: CD14(low), CD80(high), CD83(high), CD86(high), CCR7(high), HLA class I and II(high). FACS profiles were used as the selection criteria...... together with yield and morphology. Two fast DC protocols fulfilled these criteria and were selected for functional analysis. Our results demonstrate that DC generated within 5days or 48h are comparable with SDDC both phenotypically and functionally. However, we found that 48h DC were more susceptible than...... SDDC to the IL-10 inducing stimulus of TLR ligands (R848 and LPS). Thus to determine the clinical relevance of fast DC protocols in cancer settings, small phase I trials should be conducted monitoring regulatory T cells carefully....

High field, low current operation of engineering test reactors

International Nuclear Information System (INIS)

Schwartz, J.; Cohn, D.R.; Bromberg, L.; Williams, J.E.C.

1987-06-01

Steady state engineering test reactors with high field, low current operation are investigated and compared to high current, lower field concepts. Illustrative high field ETR parameters are R = 3 m, α ∼ 0.5 m, B ∼ 10 T, β = 2.2% and I = 4 MA. For similar wall loading the fusion power of an illustrative high field, low current concept could be about 50% that of a lower field device like TIBER II. This reduction could lead to a 50% decrease in tritium consumption, resulting in a substantial decrease in operating cost. Furthermore, high field operation could lead to substantially reduced current drive requirements and cost. A reduction in current drive source power on the order of 40 to 50 MW may be attainable relative to a lower field, high current design like TIBER II implying a possible cost savings on the order of $200 M. If current drive is less efficient than assumed, the savings could be even greater. Through larger β/sub p/ and aspect ratio, greater prospects for bootstrap current operation also exist. Further savings would be obtained from the reduced size of the first wall/blanket/shield system. The effects of high fields on magnet costs are very dependent on technological assumptions. Further improvements in the future may lie with advances in superconducting and structural materials

INFLUENCE OF RAMADAN FASTING ON ANAEROBIC PERFORMANCE AND RECOVERY FOLLOWING SHORT TIME HIGH INTENSITY EXERCISE

Directory of Open Access Journals (Sweden)

Umid Karli

2007-12-01

Full Text Available The aim of this study was to investigate the effects of Ramadan fasting on anaerobic power and capacity and the removal rate of lactate after short time high intensity exercise in power athletes. Ten male elite power athletes (2 wrestlers, 7 sprinters and 1 thrower, aged 20-24 yr, mean age 22.30 ± 1.25 yr participated in this study. The subjects were tested three times [3 days before the beginning of Ramadan (Pre-RF, the last 3 days of Ramadan (End-RF and the last 3 days of the 4th week after the end of Ramadan (After-RF]. Anaerobic power and capacity were measured by using the Wingate Anaerobic Test (WAnT at Pre-RF, End-RF and After- RF. Capillary blood samples for lactate analyses and heart rate recordings were taken at rest, immediately after WAnT and throughout the recovery period. Repeated measures of ANOVA indicated that there were no significant changes in body weight, body mass index, fat free mass, percentage of body fat, daily sleeping time and daily caloric intake associated with Ramadan fasting. No significant changes were found in total body water either, but urinary density measured at End-RF was significantly higher than After-RF. Similarity among peak HR and peak LA values at Pre-RF, End- RF and After-RF demonstrated that cardiovascular and metabolic stress caused by WAnT was not affected by Ramadan fasting. In addition, no influence of Ramadan fasting on anaerobic power and capacity and removal rate of LA from blood following high intensity exercise was observed. The results of this study revealed that if strength-power training is performed regularly and daily food intake, body fluid balance and daily sleeping time are maintained as before Ramadan, Ramadan fasting will not have adverse effects on body composition, anaerobic power and capacity, and LA metabolism during and after high intensity exercise in power athletes

Impact of Fast Charging on Life of EV Batteries; NREL (National Renewable Energy Laboratory)

Energy Technology Data Exchange (ETDEWEB)

Neubauer, Jeremy; Wood, Eric; Burton, Evan; Smith, Kandler; Pesaran, Ahmad

2015-05-03

Installation of fast charging infrastructure is considered by many as one of potential solutions to increase the utility and range of electric vehicles (EVs). This is expected to reduce the range anxiety of drivers of EVs and thus increase their market penetration. Level 1 and 2 charging in homes and workplaces is expected to contribute to the majority of miles driven by EVs. However, a small percentage of urban driving and most of inter-city driving could be only achieved by a fast-charging network. DC fast charging at 50 kW, 100 kW, 120 kW compared to level 1 (3.3 kW) and level 2 (6.6 kW) results in high-current charging that can adversely impact the life of the battery. In the last couple of years, we have investigated the impact of higher current rates in batteries and potential of higher temperatures and thus lower service life. Using mathematical models, we investigated the temperature increase of batteries due to higher heat generation during fast charge and have found that this could lead to higher temperatures. We compared our models with data from other national laboratories both for fine-tuning and calibration. We found that the incremental temperature rise of batteries during 1C to 3C fast charging may reduce the practical life of the batteries by less than 10% over 10 to 15 years of vehicle ownership. We also found that thermal management of batteries is needed for fast charging to prevent high temperature excursions leading to unsafe conditions.

Performance Improvement for Two-Stage Single-Phase Grid-Connected Converters Using a Fast DC Bus Control Scheme and a Novel Synchronous Frame Current Controller

Directory of Open Access Journals (Sweden)

Bingzhang Li

2017-03-01

Full Text Available Two-stage single-phase grid-connected converters are widely used in renewable energy applications. Due to the presence of a second harmonic ripple across the DC bus voltage, it is very challenging to design the DC bus voltage control scheme in single-phase grid-connected inverters. The DC bus voltage controller must filter the ripple and balance a tradeoff between low harmonic distortion and high bandwidth. This paper presents a fast DC bus voltage controller, which uses a second order digital finite impulse response (FIR notch filter in conjunction with input power feedforward scheme to ensure the steady-state and dynamic performance. To gain the input power without extra hardware, a Kalman filter is incorporated to estimate the DC bus input current. At the same time, a modulation compensation strategy is implemented to eliminate the nonlinearity of the grid current control loop, which is caused by the DC bus voltage ripple. Moreover, a novel synchronous frame current controller for single-phase systems is also introduced, and its equivalent model in stationary frame has been derived. Simulation and experimental results are provided to verify the effective of the proposed control scheme.

Elevation of Fasting Ghrelin in Healthy Human Subjects Consuming a High-Salt Diet: A Novel Mechanism of Obesity?

Directory of Open Access Journals (Sweden)

Yong Zhang

2016-05-01

Full Text Available Overweight/obesity is a chronic disease that carries an increased risk of hypertension, diabetes mellitus, and premature death. Several epidemiological studies have demonstrated a clear relationship between salt intake and obesity, but the pathophysiologic mechanisms remain unknown. We hypothesized that ghrelin, which regulates appetite, food intake, and fat deposition, becomes elevated when one consumes a high-salt diet, contributing to the progression of obesity. We, therefore, investigated fasting ghrelin concentrations during a high-salt diet. Thirty-eight non-obese and normotensive subjects (aged 25 to 50 years were selected from a rural community in Northern China. They were sequentially maintained on a normal diet for three days at baseline, a low-salt diet for seven days (3 g/day, NaCl, then a high-salt diet for seven days (18 g/day. The concentration of plasma ghrelin was measured using an immunoenzyme method (ELISA. High-salt intake significantly increased fasting ghrelin levels, which were higher during the high-salt diet (320.7 ± 30.6 pg/mL than during the low-salt diet (172.9 ± 8.9 pg/mL. The comparison of ghrelin levels between the different salt diets was statistically-significantly different (p < 0.01. A positive correlation between 24-h urinary sodium excretion and fasting ghrelin levels was demonstrated. Our data indicate that a high-salt diet elevates fasting ghrelin in healthy human subjects, which may be a novel underlying mechanism of obesity.

Highly efficient red electrophosphorescent devices at high current densities

International Nuclear Information System (INIS)

Wu Youzhi; Zhu Wenqing; Zheng Xinyou; Sun, Runguang; Jiang Xueyin; Zhang Zhilin; Xu Shaohong

2007-01-01

Efficiency decrease at high current densities in red electrophosphorescent devices is drastically restrained compared with that from conventional electrophosphorescent devices by using bis(2-methyl-8-quinolinato)4-phenylphenolate aluminum (BAlq) as a hole and exciton blocker. Ir complex, bis(2-(2'-benzo[4,5-α]thienyl) pyridinato-N,C 3' ) iridium (acetyl-acetonate) is used as an emitter, maximum external quantum efficiency (QE) of 7.0% and luminance of 10000cd/m 2 are obtained. The QE is still as high as 4.1% at higher current density J=100mA/cm 2 . CIE-1931 co-ordinates are 0.672, 0.321. A carrier trapping mechanism is revealed to dominate in the process of electroluminescence

High normal fasting glucose level in obese youth: a marker for insulin resistance and beta cell dysregulation.

LENUS (Irish Health Repository)

O'Malley, G

2010-06-01

A high but normal fasting plasma glucose level in adults is a risk factor for future development of type 2 diabetes mellitus and cardiovascular disease. We investigated whether normal fasting plasma glucose levels (<5.60 mmol\\/l) are associated with decreases in insulin sensitivity and beta cell function, as well as an adverse cardiovascular profile in obese youth.

Rule-Based Reasoning Is Fast and Belief-Based Reasoning Can Be Slow: Challenging Current Explanations of Belief-Bias and Base-Rate Neglect

Science.gov (United States)

Newman, Ian R.; Gibb, Maia; Thompson, Valerie A.

2017-01-01

It is commonly assumed that belief-based reasoning is fast and automatic, whereas rule-based reasoning is slower and more effortful. Dual-Process theories of reasoning rely on this speed-asymmetry explanation to account for a number of reasoning phenomena, such as base-rate neglect and belief-bias. The goal of the current study was to test this…

Los Alamos compact toroid, fast-liner, and high-density Z-pinch programs

Energy Technology Data Exchange (ETDEWEB)

Linford, R.K.; Sherwood, A.R.; Hammel, J.E.

1981-03-01

The Compact Toroid (CT) and High Density Z-Pinch (HDZP) are two of the plasma configurations presently being studied at Los Alamos. The purpose of these two programs, plus the recently terminated (May 1979) Fast Liner (FL) program, is summarized in this section along with a brief description of the experimental facilities. The remaining sections summarize the recent results and the experimental status.

Fast magnetic reconnection supported by sporadic small-scale Petschek-type shocks

International Nuclear Information System (INIS)

Shibayama, Takuya; Nakabou, Takashi; Kusano, Kanya; Miyoshi, Takahiro; Vekstein, Grigory

2015-01-01

Standard magnetohydrodynamic (MHD) theory predicts reconnection rate that is far too slow to account for a wide variety of reconnection events observed in space and laboratory plasmas. Therefore, it was commonly accepted that some non-MHD (kinetic) effects play a crucial role in fast reconnection. A recently renewed interest in simple MHD models is associated with the so-called plasmoid instability of reconnecting current sheets. Although it is now evident that this effect can significantly enhance the rate of reconnection, many details of the underlying multiple-plasmoid process still remain controversial. Here, we report results of a high-resolution computer simulation which demonstrate that fast albeit intermittent magnetic reconnection is sustained by numerous small-scale Petschek-type shocks spontaneously formed in the current sheet due to its plasmoid instability

Fast magnetic reconnection supported by sporadic small-scale Petschek-type shocks

Energy Technology Data Exchange (ETDEWEB)

Shibayama, Takuya, E-mail: shibayama@stelab.nagoya-u.ac.jp; Nakabou, Takashi [Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Kusano, Kanya [Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Kanazawa-ku, Yokohama, Kanagawa 236-0001 (Japan); Miyoshi, Takahiro [Department of Physical Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Vekstein, Grigory [Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL (United Kingdom)

2015-10-15

Standard magnetohydrodynamic (MHD) theory predicts reconnection rate that is far too slow to account for a wide variety of reconnection events observed in space and laboratory plasmas. Therefore, it was commonly accepted that some non-MHD (kinetic) effects play a crucial role in fast reconnection. A recently renewed interest in simple MHD models is associated with the so-called plasmoid instability of reconnecting current sheets. Although it is now evident that this effect can significantly enhance the rate of reconnection, many details of the underlying multiple-plasmoid process still remain controversial. Here, we report results of a high-resolution computer simulation which demonstrate that fast albeit intermittent magnetic reconnection is sustained by numerous small-scale Petschek-type shocks spontaneously formed in the current sheet due to its plasmoid instability.

Plasma erosion opening switch in the double-pulse operation mode of a high-current electron accelerator

International Nuclear Information System (INIS)

Isakov, I.F.; Lopatin, V.S.; Remnev, G.E.

1987-01-01

This paper reports the results of investigations of the operation of a fast current opening switch, with a 10/sup 13/-10/sup 16/ plasma density produced either by dielectric surface flashover or by explosive emission of graphite. A series of two pulses was applied to two diodes in parallel. The first pulse produced plasma in the first diode which closed that diode gap by the arrival time of the second pulse. The first, shorted, diode then acted as an erosion switch for the second pulse. A factor of 2.5-3 power multiplication was obtained under optimum conditions. The opening-switch resistance during the magnetic insulation phase, neglecting the electron losses between the switch and the generating diode, exceeded 100 Ω. The duration of the rapid opening phase was less than 5 ns under optimum conditions. This method of plasma production does not require external plasma sources, and permits a wide variation of plasma density, which in turn allows high inductor currents and stored energies

Current and high-β sheets in CIR streams: statistics and interaction with the HCS and the magnetosphere

Science.gov (United States)

Potapov, A. S.

2018-04-01

Thirty events of CIR streams (corotating interaction regions between fast and slow solar wind) were analyzed in order to study statistically plasma structure within the CIR shear zones and to examine the interaction of the CIRs with the heliospheric current sheet (HCS) and the Earth's magnetosphere. The occurrence of current layers and high-beta plasma sheets in the CIR structure has been estimated. It was found that on average, each of the CIR streams had four current layers in its structure with a current density of more than 0.12 A/m2 and about one and a half high-beta plasma regions with a beta value of more than five. Then we traced how and how often the high-speed stream associated with the CIR can catch up with the heliospheric current sheet (HCS) and connect to it. The interface of each fourth CIR stream coincided in time within an hour with the HCS, but in two thirds of cases, the CIR connection with the HCS was completely absent. One event of the simultaneous observation of the CIR stream in front of the magnetosphere by the ACE satellite in the vicinity of the L1 libration point and the Wind satellite in the remote geomagnetic tail was considered in detail. Measurements of the components of the interplanetary magnetic field and plasma parameters showed that the overall structure of the stream is conserved. Moreover, some details of the fine structure are also transferred through the magnetosphere. In particular, the so-called "magnetic hole" almost does not change its shape when moving from L1 point to a neighborhood of L2 point.

Simple, high current, antimony ion source

International Nuclear Information System (INIS)

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 μA at 1 kV extraction voltage. A discharge occurred in the source at a pressure of 6 x 10 -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 8 x 10 -9 and 1.8 x 10 11 cm -3 , respectively

Re-entering fast ion effects on NBI heating power in high-beta plasmas of the Large Helical Device

International Nuclear Information System (INIS)

Seki, Ryosuke; Watanabe, Kiyomasa; Funaba, Hisamichi; Suzuki, Yasuhiro; Sakakibara, Satoru; Ohdachi, Satoshi; Matsumoto, Yutaka; Hamamatsu, Kiyotaka

2011-10-01

We calculate the heating power of the neutral beam injection (NBI) in the = 4.8% high-beta discharge achieved in the Large Helical Device (LHD). We investigate the difference of the heating efficiency and the heating power profile between with and without the re-entering fast ion effects. When the re-entering fast ion effects are taken into account, the heating efficiency in the co injection of the NBI (co-NBI case) is improved and it is about 1.8 times larger than that without the re-entering effects. In contrast, the heating efficiency with the re-entering effects in the counter injection of the NBI (ctr-NBI case) rarely differs from that without the re-entering ones. We also study the re-entering fast ion effects on the transport properties in the LHD high beta discharges. It is found that the tendency of the thermal conductivities on the beta value is not so much sensitive with and without the re-entering effects. In addition, we investigate the difference in the re-entering fast ion effects caused by the field strength and the magnetic configuration. In the co-NBI case, the re-entering fast ion effects on the heating efficiency increases with the decrease of the field strength. In the contrast, the re-entering fast ion effects in the ctr-NBI case rarely differs by changing the field strength. (author)

Fast BIA-amperometric determination of isoniazid in tablets.

Science.gov (United States)

Quintino, Maria S M; Angnes, Lúcio

2006-09-26

This paper proposes a new, fast and precise method to analyze isoniazid based on the electrochemical oxidation of the analyte at a glassy carbon electrode in 0.1M NaOH. The quantification was performed utilizing amperometry associated with batch injection analysis (BIA) technique. Fast sequential analysis (60 determinations h(-1)) in an unusually wide linear dynamic range (from 2.5 x 10(-8) to 1.0 x 10(-3)M), with high sensitivity and low limits of detection (4.1 x 10(-9)M) and quantification (1.4 x 10(-8)M), was achieved. Such characteristics allied to a good repeatability of the current responses (relative standard deviation of 0.79% for 30 measurements), were explored for the specific determination of isoniazid in isoniazid-rifampin tablet.

Future Assets, Student Talent (FAST)

Science.gov (United States)

1992-01-01

Future Assets, Student Talent (FAST) motivates and prepares talented students with disabilities to further their education and achieve High Tech and professional employment. The FAST program is managed by local professionals, business, and industry leaders; it is modeled after High School High Tech project TAKE CHARGE started in Los Angeles in 1983. Through cooperative efforts of Alabama Department of Education, Vocational Rehabilitation, Adult and Children Services, and the President's Committee on Employment of People with Disabilities, north central Alabama was chosen as the second site for a High School High Tech project. In 1986 local business, industry, education, government agencies, and rehabilitation representatives started FAST. The program objectives and goals, results and accomplishments, and survey results are included.

The ATLAS Fast Tracker and Tracking at the High-Luminosity LHC

CERN Document Server