Science.gov

Sample records for beam current transformer

  1. LANSCE beam current limiter

    SciTech Connect

    Gallegos, F.R.

    1996-06-01

    The Radiation Security System (RSS) at the Los Alamos Neutron Science Center (LANSCE) provides personnel protection from prompt radiation due to accelerated beam. Active instrumentation, such as the Beam Current Limiter, is a component of the RSS. The current limiter is designed to limit the average current in a beam line below a specific level, thus minimizing the maximum current available for a beam spill accident. The beam current limiter is a self-contained, electrically isolated toroidal beam transformer which continuously monitors beam current. It is designed as fail-safe instrumentation. The design philosophy, hardware design, operation, and limitations of the device are described.

  2. A new method to calculate the beam charge for an integrating current transformer

    SciTech Connect

    Wu Yuchi; Han Dan; Zhu Bin; Dong Kegong; Tan Fang; Gu Yuqiu

    2012-09-15

    The integrating current transformer (ICT) is a magnetic sensor widely used to precisely measure the charge of an ultra-short-pulse charged particle beam generated by traditional accelerators and new laser-plasma particle accelerators. In this paper, we present a new method to calculate the beam charge in an ICT based on circuit analysis. The output transfer function shows an invariable signal profile for an ultra-short electron bunch, so the function can be used to evaluate the signal quality and calculate the beam charge through signal fitting. We obtain a set of parameters in the output function from a standard signal generated by an ultra-short electron bunch (about 1 ps in duration) at a radio frequency linear electron accelerator at Tsinghua University. These parameters can be used to obtain the beam charge by signal fitting with excellent accuracy.

  3. LANSCE beam current limiter

    SciTech Connect

    Gallegos, F.R.

    1997-01-01

    The Radiation Security System (RSS) at the Los Alamos Neutron Science Center (LANSCE) provides personnel protection from prompt radiation due to accelerated beam. Active instrumentation, such as the beam current limiter, is a component of the RSS. The current limiter is designed to limit the average current in a beamline below a specific level, thus minimizing the maximum current available for a beam spill accident. The beam current limiter is a self-contained, electrically isolated toroidal beam transformer which continuously monitors beam current. It is designed as fail-safe instrumentation. The design philosophy, hardware design, operation, and limitations of the device are described. {copyright} {ital 1997 American Institute of Physics.}

  4. Optimization of Drive-Bunch Current Profile for Enhanced Transformer Ratio in Beam-Driven Acceleration Techniques

    SciTech Connect

    Lemery, F.; Mihalcea, D.; Prokop, C.R.; Piot, P.; /Northern Illinois U. /Fermilab

    2012-07-08

    In recent years, wakefield acceleration has gained attention due to its high acceleration gradients and cost effectiveness. In beam-driven wakefield acceleration, a critical parameter to optimize is the transformer ratio. It has been shown that current shaping of electron beams allows for enhanced (> 2) transformer ratios. In this paper we present the optimization of the pulse shape of the drive bunch for dielectric-wakefield acceleration.

  5. A modified beam-to-earth transformation to measure short-wavelength internal waves with an acoustic Doppler current profiler

    USGS Publications Warehouse

    Scotti, A.; Butman, B.; Beardsley, R.C.; Alexander, P.S.; Anderson, S.

    2005-01-01

    The algorithm used to transform velocity signals from beam coordinates to earth coordinates in an acoustic Doppler current profiler (ADCP) relies on the assumption that the currents are uniform over the horizontal distance separating the beams. This condition may be violated by (nonlinear) internal waves, which can have wavelengths as small as 100-200 m. In this case, the standard algorithm combines velocities measured at different phases of a wave and produces horizontal velocities that increasingly differ from true velocities with distance from the ADCP. Observations made in Massachusetts Bay show that currents measured with a bottom-mounted upward-looking ADCP during periods when short-wavelength internal waves are present differ significantly from currents measured by point current meters, except very close to the instrument. These periods are flagged with high error velocities by the standard ADCP algorithm. In this paper measurements from the four spatially diverging beams and the backscatter intensity signal are used to calculate the propagation direction and celerity of the internal waves. Once this information is known, a modified beam-to-earth transformation that combines appropriately lagged beam measurements can be used to obtain current estimates in earth coordinates that compare well with pointwise measurements. ?? 2005 American Meteorological Society.

  6. Direct current transformer

    NASA Technical Reports Server (NTRS)

    Khanna, S. M.; Urban, E. W. (Inventor)

    1979-01-01

    A direct current transformer in which the primary consists of an elongated strip of superconductive material, across the ends of which is direct current potential is described. Parallel and closely spaced to the primary is positioned a transformer secondary consisting of a thin strip of magnetoresistive material.

  7. LANSCE Beam Current Limiter (XL)

    SciTech Connect

    Gallegos, F.R.; Hall, M.J.

    1997-01-01

    The Radiation Security System (RSS) at the Los Alamos Neutron Science Center (LANSCE) is an engineered safety system that provides personnel protection from prompt radiation due to accelerated proton beams. The Beam Current Limiter (XL), as an active component of the RSS, limits the maximum average current in a beamline, thus the current available for a beam spill accident. Exceeding the pre-set limit initiates action by the RSS to mitigate the hazard (insertion of beam stoppers in the low energy beam transport). The beam limiter is an electrically isolated, toroidal transformer and associated electronics. The device was designed to continuously monitor beamline currents independent of any external timing. Fail-safe operation was a prime consideration in its development. Fail-safe operation is defined as functioning as intended (due to redundant circuitry), functioning with a more sensitive fault threshold, or generating a fault condition. This report describes the design philosophy, hardware, implementation, operation, and limitations of the device.

  8. Nondestructive synchronous beam current monitor

    SciTech Connect

    Covo, Michel Kireeff

    2014-12-15

    A fast current transformer is mounted after the deflectors of the Berkeley 88-Inch Cyclotron. The measured signal is amplified and connected to the input of a lock-in amplifier. The lock-in amplifier performs a synchronous detection of the signal at the cyclotron second harmonic frequency. The magnitude of the signal detected is calibrated against a Faraday cup and corresponds to the beam intensity. It has exceptional resolution, long term stability, and can measure the beam current leaving the cyclotron as low as 1 nA.

  9. Beam current sensor

    DOEpatents

    Kuchnir, Moyses; Mills, Frederick E.

    1987-01-01

    A current sensor for measuring the DC component of a beam of charged particles employs a superconducting pick-up loop probe, with twisted superconducting leads in combination with a Superconducting Quantum Interference Device (SQUID) detector. The pick-up probe is in the form of a single-turn loop, or a cylindrical toroid, through which the beam is directed and within which a first magnetic flux is excluded by the Meisner effect. The SQUID detector acts as a flux-to-voltage converter in providing a current to the pick-up loop so as to establish a second magnetic flux within the electrode which nulls out the first magnetic flux. A feedback voltage within the SQUID detector represents the beam current of the particles which transit the pick-up loop. Meisner effect currents prevent changes in the magnetic field within the toroidal pick-up loop and produce a current signal independent of the beam's cross-section and its position within the toroid, while the combination of superconducting elements provides current measurement sensitivites in the nano-ampere range.

  10. Beam current sensor

    DOEpatents

    Kuchnir, M.; Mills, F.E.

    1984-09-28

    A current sensor for measuring the dc component of a beam of charged particles employs a superconducting pick-up loop probe, with twisted superconducting leads in combination with a Superconducting Quantum Interference Device (SQUID) detector. The pick-up probe is in the form of a single-turn loop, or a cylindrical toroid, through which the beam is directed and within which a first magnetic flux is excluded by the Meisner effect. The SQUID detector acts as a flux-to-voltage converter in providing a current to the pick-up loop so as to establish a second magnetic flux within the electrode which nulls out the first magnetic flux. A feedback voltage within the SQUID detector represents the beam current of the particles which transit the pick-up loop. Meisner effect currents prevent changes in the magnetic field within the toroidal pick-up loop and produce a current signal independent of the beam's cross-section and its position within the toroid, while the combination of superconducting elements provides current measurement sensitivities in the nano-ampere range.

  11. Temperature-sensitive junction transformations for mid-wavelength HgCdTe photovoltaic infrared detector arrays by laser beam induced current microscope

    SciTech Connect

    Qiu, Weicheng; Hu, Weida Lin, Tie; Yin, Fei; Zhang, Bo; Chen, Xiaoshuang; Lu, Wei; Cheng, Xiang'ai Wang, Rui

    2014-11-10

    In this paper, we report on the disappearance of the photosensitive area extension effect and the unusual temperature dependence of junction transformation for mid-wavelength, n-on-p HgCdTe photovoltaic infrared detector arrays. The n-type region is formed by B{sup +} ion implantation on Hg-vacancy-doped p-type HgCdTe. Junction transformations under different temperatures are visually captured by a laser beam induced current microscope. A physical model of temperature dependence on junction transformation is proposed and demonstrated by using numerical simulations. It is shown that Hg-interstitial diffusion and temperature activated defects jointly lead to the p-n junction transformation dependence on temperature, and the weaker mixed conduction compared with long-wavelength HgCdTe photodiode contributes to the disappearance of the photosensitive area extension effect in mid-wavelength HgCdTe infrared detector arrays.

  12. 60. VIEW OF THE CURRENT TRANSFORMER VAULT. THIS CURRENT TRANSFORMER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    60. VIEW OF THE CURRENT TRANSFORMER VAULT. THIS CURRENT TRANSFORMER WAS USED TO SENSE HIGH CURRENT BEING GENERATED ON GENERATOR NUMBER 3 AND REDUCE IT TO A LOWER, EXACT ANALOG VALUE THAT COULD BE SAFELY HANDLED AND MONITORED WITH THE CONTROL CIRCUITRY. THE CURRENT TRANSFORMER IS LOCATED IN THE CENTER OF THE PHOTOGRAPH. THE CONNECTING BUS ABOVE THE TRANSFORMER WAS REMOVED FOR SALVAGE. - New York, New Haven & Hartford Railroad, Cos Cob Power Plant, Sound Shore Drive, Greenwich, Fairfield County, CT

  13. Charged particle beam current monitoring tutorial

    SciTech Connect

    Webber, R.C.

    1994-10-01

    A tutorial presentation is made on topics related to the measurement of charged particle beam currents. The fundamental physics of electricity and magnetism pertinent to the problem is reviewed. The physics is presented with a stress on its interpretation from an electrical circuit theory point of view. The operation of devices including video pulse current transformers, direct current transformers, and gigahertz bandwidth wall current style transformers is described. Design examples are given for each of these types of devices. Sensitivity, frequency response, and physical environment are typical parameters which influence the design of these instruments in any particular application. Practical engineering considerations, potential pitfalls, and performance limitations are discussed.

  14. DC-Compensated Current Transformer.

    PubMed

    Ripka, Pavel; Draxler, Karel; Styblíková, Renata

    2016-01-01

    Instrument current transformers (CTs) measure AC currents. The DC component in the measured current can saturate the transformer and cause gross error. We use fluxgate detection and digital feedback compensation of the DC flux to suppress the overall error to 0.15%. This concept can be used not only for high-end CTs with a nanocrystalline core, but it also works for low-cost CTs with FeSi cores. The method described here allows simultaneous measurements of the DC current component. PMID:26805830

  15. LEDA beam diagnostics instrumentation: Beam current measurement

    NASA Astrophysics Data System (ADS)

    Barr, D.; Day, L.; Gilpatrick, J. D.; Kasemir, K.-U.; Martinez, D.; Power, J. F.; Shurter, R.; Stettler, M.

    2000-11-01

    The Low Energy Demonstration Accelerator (LEDA) facility located at Los Alamos National Laboratory (LANL) accelerates protons to an energy of 6.7 MeV and current of 100 mA operating in either a pulsed or cw mode. Two types of current measurements are used. The first is an AC or pulsed-current measurement which uses three LANL built toroids. They are placed in the beamline in such a way as to measure important transmission parameters and act as a differential current-loss machine protection system. The second system is a DC current measurement used to measure cw beam characteristics and uses toroids from Bergoz Inc. There are two of these systems, so they can also be used for transmission measurements. The AC system uses custom processing electronics whereas the DC system uses a modified Bergoz® electronics system. Both systems feature data acquisition via a series of custom TMS320C40 Digital Signal Processing (DSP) boards. Of special interest to this paper is the operation of these systems, the calibration technique, the differential current loss measurements and fast-protection processing, current droop characteristics for the AC system, and existing system noise levels. This paper will also cover the DSP system operations and their interaction with the main accelerator control system.

  16. Solid-state current transformer

    NASA Technical Reports Server (NTRS)

    Farnsworth, D. L. (Inventor)

    1976-01-01

    A signal transformation network which is uniquely characterized to exhibit a very low input impedance while maintaining a linear transfer characteristic when driven from a voltage source and when quiescently biased in the low microampere current range is described. In its simplest form, it consists of a tightly coupled two transistor network in which a common emitter input stage is interconnected directly with an emitter follower stage to provide virtually 100 percent negative feedback to the base input of the common emitter stage. Bias to the network is supplied via the common tie point of the common emitter stage collector terminal and the emitter follower base stage terminal by a regulated constant current source, and the output of the circuit is taken from the collector of the emitter follower stage.

  17. Coherent signal-subspace transformation beam former

    NASA Astrophysics Data System (ADS)

    Yang, J.-F.; Kaveh, M.

    1990-08-01

    A family of coherent signal-subspace transformation (CST) preprocessors for improving the performance of beam formers is presented. The proposed beam former includes a CST preprocessor followed by a frequency-independent mulling procedure. If the exact CST preprocessor is used, it is shown that the steering and nulling responses of the CST beam former become frequency independent. This CST beam former is also interpreted as a wideband minimum-variance distortionless response (MVDR) beam former for minimizing the total interference and noise powers. Several classes of the CST matrix are proposed and discussed. Unlike the traditional linearly constrained beam formers, the CST beam former effectively nulls the narrowband and wideband correlated interfences(s). Simulation results show that even low-order approximate CST preprocessors substantially improve the nulling and the steering bandwidth of general arrays.

  18. Effective shielding to measure beam current from an ion source

    SciTech Connect

    Bayle, H.; Delferrière, O.; Gobin, R.; Harrault, F.; Marroncle, J.; Senée, F.; Simon, C.; Tuske, O.

    2014-02-15

    To avoid saturation, beam current transformers must be shielded from solenoid, quad, and RFQ high stray fields. Good understanding of field distribution, shielding materials, and techniques is required. Space availability imposes compact shields along the beam pipe. This paper describes compact effective concatenated magnetic shields for IFMIF-EVEDA LIPAc LEBT and MEBT and for FAIR Proton Linac injector. They protect the ACCT Current Transformers beyond 37 mT radial external fields. Measurements made at Saclay on the SILHI source are presented.

  19. Transformer ratio improvement for beam based plasma accelerators

    SciTech Connect

    O'Shea, Brendan; Rosenzweig, James; Barber, Samuel; Fukasawa, Atsushi; Williams, Oliver; Muggli, Patric; Yakimenko, Vitaly; Kusche, Karl

    2012-12-21

    Increasing the transformer ratio of wakefield accelerating systems improves the viability of present novel accelerating schemes. The use of asymmetric bunches to improve the transformer ratio of beam based plasma systems has been proposed for some time[1, 2] but suffered from lack appropriate beam creation systems. Recently these impediments have been overcome [3, 4] and the ability now exists to create bunches with current profiles shaped to overcome the symmetric beam limit of R {<=} 2. We present here work towards experiments designed to measure the transformer ratio of such beams, including theoretical models and simulations using VORPAL (a 3D capable PIC code) [5]. Specifically we discuss projects to be carried out in the quasi-nonlinear regime [6] at the UCLA Neptune Laboratory and the Accelerator Test Facility at Brookhaven National Lab.

  20. Transformation-optical Fan-beam Synthesis

    PubMed Central

    Yang, Rui; Kong, Xianghui; Wang, Hui; Su, He; Lei, Zhenya; Wang, Jing; Zhang, Aofang; Chen, Lei

    2016-01-01

    Gradient-index dielectric lenses are generated based on the coordinate transformation by compressing the homogeneous air spaces quasi-conformally towards and outwards the primary source. The three-dimensional modeling is then performed through revolving the prescribed transformational media 180 degrees around the focal point to reach the architecture of barrel-vaults. It is found that all these two- and three-dimensional transformation-optical designs are capable of producing fan-beams efficiently over a broad frequency range with their main lobes possessing the narrow beamwidth in one dimension and the wide beamwidth in the other, while having the great ability of the wide angular scanning. Finally, we propose to construct such four types of fan-beam lenses through multiple-layered dielectrics with non-uniformed perforations and experimentally demonstrate their excellent performances in the fan-beam synthesis. PMID:26847048

  1. Transformation-optical Fan-beam Synthesis

    NASA Astrophysics Data System (ADS)

    Yang, Rui; Kong, Xianghui; Wang, Hui; Su, He; Lei, Zhenya; Wang, Jing; Zhang, Aofang; Chen, Lei

    2016-02-01

    Gradient-index dielectric lenses are generated based on the coordinate transformation by compressing the homogeneous air spaces quasi-conformally towards and outwards the primary source. The three-dimensional modeling is then performed through revolving the prescribed transformational media 180 degrees around the focal point to reach the architecture of barrel-vaults. It is found that all these two- and three-dimensional transformation-optical designs are capable of producing fan-beams efficiently over a broad frequency range with their main lobes possessing the narrow beamwidth in one dimension and the wide beamwidth in the other, while having the great ability of the wide angular scanning. Finally, we propose to construct such four types of fan-beam lenses through multiple-layered dielectrics with non-uniformed perforations and experimentally demonstrate their excellent performances in the fan-beam synthesis.

  2. A transmission-loss monitor using current transformers

    SciTech Connect

    Power, J.F.; Gilpatrick, J.D.; Jason, A.J.

    1993-12-01

    A system for measuring the amount of beam-charge loss in a linear-accelerator structure has been developed that uses a pair of beam-current transformers, otherwise used to monitor the linac beam current. This system is necessary to enable the Ground Test Accelerator (GTA) fast-protect system to shut off the accelerated beam in the event of a beam loss that would deposit sufficient energy to damage the accelerator structure. The present GTA accelerator consists of a 2.5-MeV, H{sup {minus}} RFQ, an intermediate matching section (IMS) and a single DTL cavity with an output energy of 3.2-MeV and transmitted current of 35 mA. Based on the RFQ output beam, melting of the copper structures will occur when about 40 nC of beam is deposited in a point loss. For a grazing angle of 30 mrad, up to 640 nC may be tolerated. The beam-current-transmission-loss monitor (BCTLM) system in conjunction with the fast-protect system measures the amount of beam loss between two toroidal beam-current monitors and automatically terminates the macropulse when the integrated loss reaches a predetermined set point. The design and operation of the BCTLM system used in the IMS and DTL section of the accelerator is described.

  3. High transformer ratio drive beams for wakefield accelerator studies

    SciTech Connect

    England, R. J.; Ng, C.-K.; Frederico, J.; Hogan, M. J.; Litos, M.; Muggli, P.; Joshi, C.; An, W.; Andonian, G.; Mori, W.; Lu, W.

    2012-12-21

    For wakefield based acceleration schemes, use of an asymmetric (or linearly ramped) drive bunch current profile has been predicted to enhance the transformer ratio and generate large accelerating wakes. We discuss plans and initial results for producing such bunches using the 20 to 23 GeV electron beam at the FACET facility at SLAC National Accelerator Laboratory and sending them through plasmas and dielectric tubes to generate transformer ratios greater than 2 (the limit for symmetric bunches). The scheme proposed utilizes the final FACET chicane compressor and transverse collimation to shape the longitudinal phase space of the beam.

  4. Beam coordinate transformations from DICOM to DOSXYZnrc.

    PubMed

    Zhan, Lixin; Jiang, Runqing; Osei, Ernest K

    2012-12-21

    Digital imaging and communications in medicine (DICOM) format is the de facto standard for communications between therapeutic and diagnostic modalities. A plan generated by a treatment planning system (TPS) is often exported in DICOM format. BEAMnrc/DOSXYZnrc is a widely used Monte Carlo (MC) package for modelling the Linac head and simulating dose delivery in radiotherapy. It has its own definition of beam orientation, which is not in compliance with the one defined in the DICOM standard. MC dose calculations using information from TPS generated plans require transformation of beam orientations to the DOSXYZnrc coordinate system (c.s.) and the transformation is non-trivial. There have been two studies on the coordinate transformations. The transformation equation sets derived have been helpful to BEAMnrc/DOSXYZnrc users. However, the transformation equation sets are complex mathematically and not easy to program. In this study, we derive a new set of transformation equations, which are more compact, easily understandable, and easier for computational implementation. The derivation of the polar angle θ and the azimuthal angle φ used by DOSXYZnrc is similar to the existing studies by applying a series of rotations to a vector in DICOM patient c.s. The derivation of the beam rotation ϕ(col) for DOSXYZnrc, however, is different. It is obtained by a direct combination of the actual collimator rotation with the projection of the couch rotation to the collimator rotating plane. Verification of the transformation has been performed using clinical plans. The comparisons between TPS and MC results show very good geometrical agreement for field placements, together with good agreement in dose distributions. PMID:23175216

  5. Beam coordinate transformations from DICOM to DOSXYZnrc

    NASA Astrophysics Data System (ADS)

    Zhan, Lixin; Jiang, Runqing; Osei, Ernest K.

    2012-12-01

    Digital imaging and communications in medicine (DICOM) format is the de facto standard for communications between therapeutic and diagnostic modalities. A plan generated by a treatment planning system (TPS) is often exported in DICOM format. BEAMnrc/DOSXYZnrc is a widely used Monte Carlo (MC) package for modelling the Linac head and simulating dose delivery in radiotherapy. It has its own definition of beam orientation, which is not in compliance with the one defined in the DICOM standard. MC dose calculations using information from TPS generated plans require transformation of beam orientations to the DOSXYZnrc coordinate system (c.s.) and the transformation is non-trivial. There have been two studies on the coordinate transformations. The transformation equation sets derived have been helpful to BEAMnrc/DOSXYZnrc users. However, the transformation equation sets are complex mathematically and not easy to program. In this study, we derive a new set of transformation equations, which are more compact, easily understandable, and easier for computational implementation. The derivation of the polar angle θ and the azimuthal angle φ used by DOSXYZnrc is similar to the existing studies by applying a series of rotations to a vector in DICOM patient c.s. The derivation of the beam rotation ϕcol for DOSXYZnrc, however, is different. It is obtained by a direct combination of the actual collimator rotation with the projection of the couch rotation to the collimator rotating plane. Verification of the transformation has been performed using clinical plans. The comparisons between TPS and MC results show very good geometrical agreement for field placements, together with good agreement in dose distributions.

  6. An integrating current transformer for fast extraction from the HIRFL-CSR main ring

    NASA Astrophysics Data System (ADS)

    Wu, Jun-Xia; Zheng, Jian-Hua; Zhao, Tie-Cheng; Mao, Rui-Shi; Yin, Yan; Yuan, You-Jin; Yang, Jian-Cheng

    2010-01-01

    For any experiment that uses the beam of an accelerator, monitoring the beam intensity is always an important concern. It is particularly useful if one can continuously measure the beam current without disturbing the beam. We report here on test experiments for an Integrating Current Transformer (ICT) used to measure fast extraction beams from the HIRFL-CSR main ring (CSRm). The laboratory tests and beam intensity measurement results are presented in this paper. The influence of the kicker noise is also analyzed.

  7. In-line beam current monitor

    NASA Astrophysics Data System (ADS)

    Ekdahl, C. A., Jr.; Frost, C. A.

    1984-11-01

    An intense relativistic electron beam current monitor for a gas neutralized beam transport line includes a first foil for conducting plasma current to the wall where it is measured as it traverses an inductive loop formed by a cavity in the wall. An insulator foil separates the first foil from a second conducting foil which returns the current to the plasma environment.

  8. In-line beam current monitor

    DOEpatents

    Ekdahl, Jr., Carl A.; Frost, Charles A.

    1986-01-01

    An intense relativistic electron beam current monitor for a gas neutralized beam transport line includes a first foil for conducting plasma current to the wall where it is measured as it traverses an inductive loop formed by a cavity in the wall. An insulator foil separates the first foil from a second conducting foil which returns the current to the plasma environment.

  9. In-line beam current monitor

    DOEpatents

    Ekdahl, C.A. Jr.; Frost, C.A.

    1984-11-13

    An intense relativistic electron beam current monitor for a gas neutralized beam transport line includes a first foil for conducting plasma current to the wall where it is measured as it traverses an inductive loop formed by a cavity in the wall. An insulator foil separates the first foil from a second conducting foil which returns the current to the plasma environment.

  10. Effective shielding to measure beam current from an ion source.

    PubMed

    Bayle, H; Delferrière, O; Gobin, R; Harrault, F; Marroncle, J; Senée, F; Simon, C; Tuske, O

    2014-02-01

    To avoid saturation, beam current transformers must be shielded from solenoid, quad, and RFQ high stray fields. Good understanding of field distribution, shielding materials, and techniques is required. Space availability imposes compact shields along the beam pipe. This paper describes compact effective concatenated magnetic shields for IFMIF-EVEDA LIPAc LEBT and MEBT and for FAIR Proton Linac injector. They protect the ACCT Current Transformers beyond 37 mT radial external fields. Measurements made at Saclay on the SILHI source are presented. PMID:24593447

  11. Precision Absolute Beam Current Measurement of Low Power Electron Beam

    SciTech Connect

    Ali, M. M.; Bevins, M. E.; Degtiarenko, P.; Freyberger, A.; Krafft, G. A.

    2012-11-01

    Precise measurements of low power CW electron beam current for the Jefferson Lab Nuclear Physics program have been performed using a Tungsten calorimeter. This paper describes the rationale for the choice of the calorimeter technique, as well as the design and calibration of the device. The calorimeter is in use presently to provide a 1% absolute current measurement of CW electron beam with 50 to 500 nA of average beam current and 1-3 GeV beam energy. Results from these recent measurements will also be presented.

  12. Apparatus and methods for continuous beam fourier transform mass spectrometry

    DOEpatents

    McLuckey, Scott A.; Goeringer, Douglas E.

    2002-01-01

    A continuous beam Fourier transform mass spectrometer in which a sample of ions to be analyzed is trapped in a trapping field, and the ions in the range of the mass-to-charge ratios to be analyzed are excited at their characteristic frequencies of motion by a continuous excitation signal. The excited ions in resonant motions generate real or image currents continuously which can be detected and processed to provide a mass spectrum.

  13. DC-Compensated Current Transformer

    PubMed Central

    Ripka, Pavel; Draxler, Karel; Styblíková, Renata

    2016-01-01

    Instrument current transformers (CTs) measure AC currents. The DC component in the measured current can saturate the transformer and cause gross error. We use fluxgate detection and digital feedback compensation of the DC flux to suppress the overall error to 0.15%. This concept can be used not only for high-end CTs with a nanocrystalline core, but it also works for low-cost CTs with FeSi cores. The method described here allows simultaneous measurements of the DC current component. PMID:26805830

  14. High current ion beam transport using solenoids

    SciTech Connect

    Hollinger, R.; Spaedtke, P.

    2008-02-15

    In the framework of the future project FAIR several upgrade programs and construction of new facilities are in progress such as the U{sup 4+} upgrade for the existing high current injector and the new 70 MeV proton injector. For both injectors solenoids in the low energy beam transport section are foreseen to inject the beam into the following rf accelerator. The paper presents beam quality measurements of high current ion beams behind a solenoid using a slit-grid emittance measurement device, viewing targets, and a pepper pot measurement device at the high current test bench at GSI.

  15. Electronic voltage and current transformers testing device.

    PubMed

    Pan, Feng; Chen, Ruimin; Xiao, Yong; Sun, Weiming

    2012-01-01

    A method for testing electronic instrument transformers is described, including electronic voltage and current transformers (EVTs, ECTs) with both analog and digital outputs. A testing device prototype is developed. It is based on digital signal processing of the signals that are measured at the secondary outputs of the tested transformer and the reference transformer when the same excitation signal is fed to their primaries. The test that estimates the performance of the prototype has been carried out at the National Centre for High Voltage Measurement and the prototype is approved for testing transformers with precision class up to 0.2 at the industrial frequency (50 Hz or 60 Hz). The device is suitable for on-site testing due to its high accuracy, simple structure and low-cost hardware. PMID:22368510

  16. Nanowire growth by an electron beam induced massive phase transformation

    SciTech Connect

    Sood, Shantanu; Kisslinger, Kim; Gouma, Perena

    2014-11-15

    Tungsten trioxide nanowires of a high aspect ratio have been synthesized in-situ in a TEM under an electron beam of current density 14A/cm² due to a massive polymorphic reaction. Sol-gel processed pseudocubic phase nanocrystals of tungsten trioxide were seen to rapidly transform to one dimensional monoclinic phase configurations, and this reaction was independent of the substrate on which the material was deposited. The mechanism of the self-catalyzed polymorphic transition and accompanying radical shape change is a typical characteristic of metastable to stable phase transformations in nanostructured polymorphic metal oxides. A heuristic model is used to confirm the metastable to stable growth mechanism. The findings are important to the control electron beam deposition of nanowires for functional applications starting from colloidal precursors.

  17. Nanowire growth by an electron beam induced massive phase transformation

    DOE PAGESBeta

    Sood, Shantanu; Kisslinger, Kim; Gouma, Perena

    2014-11-15

    Tungsten trioxide nanowires of a high aspect ratio have been synthesized in-situ in a TEM under an electron beam of current density 14A/cm² due to a massive polymorphic reaction. Sol-gel processed pseudocubic phase nanocrystals of tungsten trioxide were seen to rapidly transform to one dimensional monoclinic phase configurations, and this reaction was independent of the substrate on which the material was deposited. The mechanism of the self-catalyzed polymorphic transition and accompanying radical shape change is a typical characteristic of metastable to stable phase transformations in nanostructured polymorphic metal oxides. A heuristic model is used to confirm the metastable to stablemore » growth mechanism. The findings are important to the control electron beam deposition of nanowires for functional applications starting from colloidal precursors.« less

  18. Beam-halo measurements in high-current proton beams

    SciTech Connect

    Allen, C.K.; Chan, K.C.D.; Colestock, P.L.; Crandall, K.R.; Garnett, R.W.; Gilpatrick, J.D.; Lysenko, W.; Qiang, J.; Schneider, J.D.; Schulze, M.E.; Sheffield, R.L.; Smith, H.V.; Wangler, T.P.

    2002-01-11

    We present results from an experimental study of the beam halo in a high-current 6.7-MeV proton beam propagating through a 52-quadrupole periodic-focusing channel. The gradients of the first four quadrupoles were independently adjusted to match or mismatch the injected beam. Emittances and beamwidths were obtained from measured profiles for comparisons with maximum emittance-growth predictions of a free-energy model and maximum halo-amplitude predictions of a particle-core model. The experimental results support both models and the present theoretical picture of halo formation.

  19. Transformer current sensor for superconducting magnetic coils

    DOEpatents

    Shen, S.S.; Wilson, C.T.

    1985-04-16

    The present invention is a current transformer for operating currents larger than 2kA (two kiloamps) that is capable of detecting a millivolt level resistive voltage in the presence of a large inductive voltage. Specifically, the present invention includes substantially cylindrical primary turns arranged to carry a primary current and substantially cylindrical secondary turns arranged coaxially with and only partially within the primary turns, the secondary turns including an active winding and a dummy winding, the active and dummy windings being coaxial, longitudinally separated and arranged to mutually cancel voltages excited by commonly experienced magnetic fields, the active winding but not the dummy winding being arranged within the primary turns.

  20. Polarized electron beams at milliampere average current

    SciTech Connect

    Poelker, Matthew

    2013-11-01

    This contribution describes some of the challenges associated with developing a polarized electron source capable of uninterrupted days-long operation at milliAmpere average beam current with polarization greater than 80%. Challenges will be presented in the context of assessing the required level of extrapolation beyond the performance of today's CEBAF polarized source operating at ~ 200 uA average current. Estimates of performance at higher current will be based on hours-long demonstrations at 1 and 4 mA. Particular attention will be paid to beam-related lifetime-limiting mechanisms, and strategies to construct a photogun that operate reliably at bias voltage > 350kV.

  1. Transformer current sensor for superconducting magnetic coils

    DOEpatents

    Shen, Stewart S.; Wilson, C. Thomas

    1988-01-01

    A transformer current sensor having primary turns carrying a primary current for a superconducting coil and secondary turns only partially arranged within the primary turns. The secondary turns include an active winding disposed within the primary turns and a dummy winding which is not disposed in the primary turns and so does not experience a magnetic field due to a flow of current in the primary turns. The active and dummy windings are wound in opposite directions or connected in series-bucking relationship, and are exposed to the same ambient magnetic field. Voltages which might otherwise develop in the active and dummy windings due to ambient magnetic fields thus cancel out. The resultant voltage is purely indicative of the rate of change of current flowing in the primary turns.

  2. Indirectly sensing accelerator beam currents for limiting maximum beam current magnitude

    DOEpatents

    Bogaty, John M.; Clifft, Benny E.; Bollinger, Lowell M.

    1995-01-01

    A beam current limiter for sensing and limiting the beam current in a particle accelerator, such as a cyclotron or linear accelerator, used in scientific research and medical treatment. A pair of independently operable capacitive electrodes sense the passage of charged particle bunches to develop an RF signal indicative of the beam current magnitude produced at the output of a bunched beam accelerator. The RF signal produced by each sensing electrode is converted to a variable DC voltage indicative of the beam current magnitude. The variable DC voltages thus developed are compared to each other to verify proper system function and are further compared to known references to detect beam currents in excess of pre-established limits. In the event of a system malfunction, or if the detected beam current exceeds pre-established limits, the beam current limiter automatically inhibits further accelerator operation. A high Q tank circuit associated with each sensing electrode provides a narrow system bandwidth to reduce noise and enhance dynamic range. System linearity is provided by injecting, into each sensing electrode, an RF signal that is offset from the bunching frequency by a pre-determined beat frequency to ensure that subsequent rectifying diodes operate in a linear response region. The system thus provides a large dynamic range in combination with good linearity.

  3. Indirectly sensing accelerator beam currents for limiting maximum beam current magnitude

    DOEpatents

    Bogaty, J.M.; Clifft, B.E.; Bollinger, L.M.

    1995-08-08

    A beam current limiter is disclosed for sensing and limiting the beam current in a particle accelerator, such as a cyclotron or linear accelerator, used in scientific research and medical treatment. A pair of independently operable capacitive electrodes sense the passage of charged particle bunches to develop an RF signal indicative of the beam current magnitude produced at the output of a bunched beam accelerator. The RF signal produced by each sensing electrode is converted to a variable DC voltage indicative of the beam current magnitude. The variable DC voltages thus developed are compared to each other to verify proper system function and are further compared to known references to detect beam currents in excess of pre-established limits. In the event of a system malfunction, or if the detected beam current exceeds pre-established limits, the beam current limiter automatically inhibits further accelerator operation. A high Q tank circuit associated with each sensing electrode provides a narrow system bandwidth to reduce noise and enhance dynamic range. System linearity is provided by injecting, into each sensing electrode, an RF signal that is offset from the bunching frequency by a pre-determined beat frequency to ensure that subsequent rectifying diodes operate in a linear response region. The system thus provides a large dynamic range in combination with good linearity. 6 figs.

  4. SPALLATION NEUTRON SOURCE BEAM CURRENT MONITOR ELECTRONICS.

    SciTech Connect

    KESSELMAN,M.; DAWSON,W.C.

    2002-05-06

    This paper will discuss the present electronics design for the beam current monitor system to be used throughout the Spallation Neutron Source (SNS) under construction at Oak Ridge National Laboratory. The beam is composed of a micro-pulse structure due to the 402.5MHz RF, and is chopped into mini-pulses of 645ns duration with a 300ns gap, providing a macro-pulse of 1060 mini-pulses repeating at a 60Hz rate. Ring beam current will vary from about 15ma peak during studies, to about 50Amps peak (design to 100 amps). A digital approach to droop compensation has been implemented and initial test results presented.

  5. Beam current controller for laser ion source

    SciTech Connect

    Okamura, Masahiro

    2014-10-28

    The present invention relates to the design and use of an ion source with a rapid beam current controller for experimental and medicinal purposes. More particularly, the present invention relates to the design and use of a laser ion source with a magnetic field applied to confine a plasma flux caused by laser ablation.

  6. Spiral-like multi-beam emission via transformation electromagnetics

    SciTech Connect

    Tichit, Paul-Henri; Burokur, Shah Nawaz Lustrac, André de

    2014-01-14

    Transformation electromagnetics offers an unconventional approach for the design of novel radiating devices. Here, we propose an electromagnetic metamaterial able to split an isotropic radiation into multiple directive beams. By applying transformations that modify distance and angles, we show how the multiple directive beams can be steered at will. We describe transformation of the metric space and the calculation of the material parameters. Different transformations are proposed for a possible physical realization through the use of engineered artificial metamaterials. Full wave simulations are performed to validate the proposed approach. The idea paves the way to interesting applications in various domains in microwave and optical regimes.

  7. Polarized electron beams at milliampere average current

    SciTech Connect

    Poelker, M.

    2013-11-07

    This contribution describes some of the challenges associated with developing a polarized electron source capable of uninterrupted days-long operation at milliAmpere average beam current with polarization greater than 80%. Challenges will be presented in the context of assessing the required level of extrapolation beyond the performance of today’s CEBAF polarized source operating at ∼ 200 uA average current. Estimates of performance at higher current will be based on hours-long demonstrations at 1 and 4 mA. Particular attention will be paid to beam-related lifetime-limiting mechanisms, and strategies to construct a photogun that operate reliably at bias voltage > 350kV.

  8. Hough Transform Based Corner Detection for Laser Beam Positioning

    SciTech Connect

    Awwal, A S

    2005-07-26

    In laser beam alignment in addition to detecting position, one must also determine the rotation of the beam. This is essential when a commissioning new laser beam for National Ignition Facility located at the Lawrence Livermore National Laboratory. When the beam is square, the positions of the corners with respect to one another provides an estimate of the rotation of the beam. This work demonstrates corner detection in the presence or absence of a second order non-uniform illumination caused by a spatial mask. The Hough transform coupled with illumination dependent pre-processing is used to determine the corner points. We show examples from simulated and real NIF images.

  9. Note: A real-time beam current density meter

    SciTech Connect

    Liu Junliang; Yu Deyang; Ruan Fangfang; Xue Yingli; Wang Wei

    2013-03-15

    We have developed a real-time beam current density meter for charged particle beams. It measures the mean current density by collimating a uniform and large diameter primary beam. The suppression of the secondary electrons and the deflection of the beam were simulated, and it was tested with a 105 keV Ar{sup 7+} ion beam.

  10. Saturation current spikes eliminated in saturable core transformers

    NASA Technical Reports Server (NTRS)

    Schwarz, F. C.

    1971-01-01

    Unsaturating composite magnetic core transformer, consisting of two separate parallel cores designed so impending core saturation causes signal generation, terminates high current spike in converter primary circuit. Simplified waveform, demonstrates transformer effectiveness in eliminating current spikes.

  11. Beam-induced graphitic carbon cage transformation from sumanene aggregates

    SciTech Connect

    Fujita, Jun-ichi Tachi, Masashi; Murakami, Katsuhisa; Sakurai, Hidehiro; Morita, Yuki; Higashibayashi, Shuhei; Takeguchi, Masaki

    2014-01-27

    We found that electron-beam irradiation of sumanene aggregates strongly enhanced their transformation into a graphitic carbon cage, having a diameter of about 20 nm. The threshold electron dose was about 32 mC/cm{sup 2} at 200 keV, but the transformation is still induced at 20 keV. The transformation sequence suggested that the cage was constructed accompanied by the dynamical movement of the transiently linked sumanene molecules in order to pile up inside the shell. Thus, bond excitation in the sumanene molecules rather than a knock-on of carbon atoms seems to be the main cause of the cage transformation.

  12. Optimization of beam transformation system for laser-diode bars.

    PubMed

    Yu, Junhong; Guo, Linhui; Wu, Hualing; Wang, Zhao; Gao, Songxin; Wu, Deyong

    2016-08-22

    An optimized beam transformation system (BTS) is proposed to improve the beam quality of laser-diode bars. Through this optimized design, the deterioration of beam quality after the BTS can be significantly reduced. Both the simulation and experimental results demonstrate that the optimized system enables the beam quality of a mini-bar (9 emitters) approximately equal to 5.0 mm × 3.6 mrad in the fast-axis and slow-axis. After beam shaping by the optimized BTS, the laser-diode beam can be coupled into a 100 μm core, 0.15 numerical aperture (NA) fiber with an output power of over 100 W and an electric-optical efficiency of 46.8%. PMID:27557249

  13. Requirements for neutral beam current drive in tokamaks

    SciTech Connect

    Dory, R.A.

    1988-01-01

    This paper contains viewgraphs on the use of neutral beam current drive in future tokamaks. Current profiles, slowing down distributions, beam destabilization of alfven waves and plasma parameters are some items covered in this paper. (DWL)

  14. Precision intercomparison of beam current monitors at CEBAF

    SciTech Connect

    Kazimi, R.; Dunham, B.; Krafft, G.A.; Legg, r.; Liang, C.; Sinclair, C.; Mamosser, J.

    1995-12-31

    The CEBAF accelerator delivers a CW electron beam at fundamental 1497 MHz, with average beam current up to 200 {mu}A. Accurate, stable nonintercepting beam current monitors are required for: setup/control, monitoring of beam current and beam losses for machine protection and personnel safety, and providing beam current information to experimental users. Fundamental frequency stainless steel RF cavities have been chosen for these beam current monitors. This paper reports on precision intercomparison between two such RF cavities, an Unser monitor, and two Faraday cups, all located in the injector area. At the low beam energy in the injector, it is straightforward to verify the high efficiency of the Faraday cups, and the Unser monitor included a wire through it to permit an absolute calibration. The cavity intensity monitors have proven capable of stable, high precision monitoring of the beam current.

  15. Transformer ratio saturation in a beam-driven wakefield accelerator

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  16. Transformer ratio saturation in a beam-driven wakefield accelerator

    SciTech Connect

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

    2015-12-15

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

  17. 59. VIEW OF FUSES AND A CURRENT TRANSFORMER LOCATED IN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    59. VIEW OF FUSES AND A CURRENT TRANSFORMER LOCATED IN THE SIGNAL POWER CONDITIONING ROOM. THE CURRENT TRANSFORMER (UPPER RIGHT) IS AN INDUCTION COUPLED SENSOR WHICH IS USED TO REDUCE HIGH CURRENT TO ANALOGOUS LOW VALUES SAFE TO USE IN CONTROL ROOM CIRCUITRY. - New York, New Haven & Hartford Railroad, Cos Cob Power Plant, Sound Shore Drive, Greenwich, Fairfield County, CT

  18. Improvements of a Beam Current Monitor by using a High Tc Current Sensor and SQUID at the RIBF

    NASA Astrophysics Data System (ADS)

    Watanabe, T.; Fukunishi, N.; Kase, M.; Kamigaito, O.; Inamori, S.; Kon, K.

    2014-05-01

    To measure a beam current non-destructively, a conventional DC current transformer (DCCT) has been used at accelerator facilities. However, the current resolution of the DCCT is worse than 1μA. This current resolution is sufficient for electron and proton accelerators in which the beam intensity is high, but it is not sufficient for lower intensity heavy-ion beams. Thus, superconducting technology has been applied to the precise measurement of the beam current. In particular, to measure the DC current of high-energy heavy-ion beams non-destructively at high resolution, a high critical temperature (HTc) superconducting quantum interference device (SQUID) beam current monitor (HTc SQUID monitor) has been developed for use in the radioactive isotope beam factory (RIBF) at RIKEN in Japan. Beginning this year, the magnetic shielding system has been greatly reinforced. The measurement resolution is determined by the signal to noise ratio, that is improved by attenuating the external magnetic noise and is mainly produced by the distribution and transmission lines from the high current power supplies. The new strong magnetic shielding system can attenuate the external magnetic noise to 10-10.

  19. Electron-Beam Induced Transformations of Layered Tin Dichalcogenides.

    PubMed

    Sutter, E; Huang, Y; Komsa, H-P; Ghorbani-Asl, M; Krasheninnikov, A V; Sutter, P

    2016-07-13

    By combining high-resolution transmission electron microscopy and associated analytical methods with first-principles calculations, we study the behavior of layered tin dichalcogenides under electron beam irradiation. We demonstrate that the controllable removal of chalcogen atoms due to electron irradiation, at both room and elevated temperatures, gives rise to transformations in the atomic structure of Sn-S and Sn-Se systems so that new phases with different properties can be induced. In particular, rhombohedral layered SnS2 and SnSe2 can be transformed via electron beam induced loss of chalcogen atoms into highly anisotropic orthorhombic layered SnS and SnSe. A striking dependence of the layer orientation of the resulting SnS-parallel to the layers of ultrathin SnS2 starting material, but slanted for transformations of thicker few-layer SnS2-is rationalized by a transformation pathway in which vacancies group into ordered S-vacancy lines, which convert via a Sn2S3 intermediate to SnS. Absence of a stable Sn2Se3 intermediate precludes this pathway for the selenides, hence SnSe2 always transforms into basal plane oriented SnSe. Our results provide microscopic insights into the transformation mechanism and show how irradiation can be used to tune the properties of layered tin chalcogenides for applications in electronics, catalysis, or energy storage. PMID:27336595

  20. Direct-Current Monitor With Flux-Reset Transformer Coupling

    NASA Technical Reports Server (NTRS)

    Canter, Stanley

    1993-01-01

    Circuit measures constant or slowly-varying unidirectional electrical current using flux-reset transformer coupling. Measurement nonintrusive in sense that no need for direct contact with wire that carries load current to be measured, and no need to install series resistive element in load-current path. Toroidal magnetic core wrapped with coil of wire placed around load-current-carrying wire, acts as transformer core, load-current-carrying wire acts as primary winding of transformer, and coil wrapped on core acts as secondary winding.

  1. Start-to-end beam dynamics simulation of double triangular current profile generation in Argonne Wakefield Accelerator

    SciTech Connect

    Ha, G.; Power, J.; Kim, S. H.; Gai, W.; Kim, K.-J.; Cho, M. H.; Namkung, W.

    2012-12-21

    Double triangular current profile (DT) gives a high transformer ratio which is the determining factor of the performance of collinear wakefield accelerator. This current profile can be generated using the emittance exchange (EEX) beam line. Argonne Wakefield Accelerator (AWA) facility plans to generate DT using the EEX beam line. We conducted start-to-end simulation for the AWA beam line using PARMELA code. Also, we discuss requirements of beam parameters for the generation of DT.

  2. Transformation of spin current by antiferromagnetic insulators

    NASA Astrophysics Data System (ADS)

    Khymyn, Roman; Lisenkov, Ivan; Tiberkevich, Vasil S.; Slavin, Andrei N.; Ivanov, Boris A.

    2016-06-01

    It is demonstrated theoretically that a thin layer of an anisotropic antiferromagnetic (AFM) insulator can effectively conduct spin current through the excitation of a pair of evanescent AFM spin wave modes. The spin current flowing through the AFM is not conserved due to the interaction between the excited AFM modes and the AFM lattice and, depending on the excitation conditions, can be either attenuated or enhanced. When the phase difference between the excited evanescent modes is close to π /2 , there is an optimum AFM thickness for which the output spin current reaches a maximum, which can significantly exceed the magnitude of the input spin current. The spin current transfer through the AFM depends on the ambient temperature and increases substantially when temperature approaches the Néel temperature of the AFM layer.

  3. Operation of the DC current transformer intensity monitors at FNAL during run II

    SciTech Connect

    Crisp, J.; Fellenz, B.; Heikkinen, D.; Ibrahim, M.A.; Meyer, T.; Vogel, G.; /Fermilab

    2012-01-01

    Circulating beam intensity measurements at FNAL are provided by five DC current transformers (DCCT), one per machine. With the exception of the DCCT in the Recycler, all DCCT systems were designed and built at FNAL. This paper presents an overview of both DCCT systems, including the sensor, the electronics, and the front-end instrumentation software, as well as their performance during Run II.

  4. Beam profile for the Herschel-SPIRE Fourier transform spectrometer.

    PubMed

    Makiwa, Gibion; Naylor, David A; Ferlet, Marc; Salji, Carl; Swinyard, Bruce; Polehampton, Edward; van der Wiel, Matthijs H D

    2013-06-01

    One of the instruments on board the Herschel Space Observatory is the Spectral and Photometric Imaging Receiver (SPIRE). SPIRE employs a Fourier transform spectrometer with feed-horn-coupled bolometers to provide imaging spectroscopy. To interpret the resultant spectral images requires knowledge of the wavelength-dependent beam, which in the case of SPIRE is complicated by the use of multimoded feed horns. In this paper we describe a series of observations and the analysis conducted to determine the wavelength dependence of the SPIRE spectrometer beam profile. PMID:23736346

  5. Suppression of current fluctuations in an intense electron beam

    SciTech Connect

    Harris, J. R.; Lewellen, J. W.

    2010-10-15

    When an intense beam encounters an aperture, the transmitted current depends on the properties of the beam and the transport channel, as well as those of the aperture itself. In some cases, an increase in the incident beam current will be exactly compensated by an increase in the incident beam area, so that the current density at the aperture remains unchanged. When this occurs, the transmitted beam current becomes independent of changes in the incident beam current, providing a passive means for suppressing current fluctuations in the beam. In this article, a key requirement for the existence of this condition is derived. This requirement is shown to be fulfilled in the case of an idealized uniform focusing channel in the small-signal limit, but to be violated when the current fluctuations are not small. Even in this case, the apertured transport system retains the ability to suppress--but not totally eliminate--fluctuations in the transmitted beam current for a wide range of incident beam currents.

  6. Online diagnoses of high current-density beams

    SciTech Connect

    Gilpatrick, J.D.

    1994-07-01

    Los Alamos National Laboratory has proposed several CW-proton-beam facilities for production of tritium or transmutation of nuclear waste with beam-current densities greater than 5 mA/mm{sup 2}. The primary beam-diagnostics-instrumentation requirement for these facilities is provision of sufficient beam information to understand and minimize beam-loss. To accomplish this task, the beam-diagnostics instrumentation must measure beam parameters such as the centroids and profiles, total integrated current, and particle loss. Noninterceptive techniques must be used for diagnosis of high-intensity CW beam at low energies due to the large quantity of power deposited in an interceptive diagnostic device by the beam. Transverse and longitudinal centroid measurements have been developed for bunched beams by measuring and processing image currents on the accelerator walls. Transverse beam-profile measurement-techniques have also been developed using the interaction of the particle beam with the background gases near the beam region. This paper will discuss these noninterceptive diagnostic Techniques.

  7. High-current beam dynamics and transport, theory and experiment

    SciTech Connect

    Reiser, M.

    1986-01-01

    Recent progress in the understanding of beam physics and technology factors determining the current and brightness of ion and electron beams in linear accelerators will be reviewed. Topics to be discussed including phase-space density constraints of particle sources, low-energy beam transport include charge neutralization, emittance growth due to mismatch, energy exchange, instabilities, nonlinear effects, and longitudinal bunching.

  8. Optomechanical control of transforming Bessel beams in a c-cut of lithium niobate

    NASA Astrophysics Data System (ADS)

    Paranin, V. D.; Karpeev, S. V.; Khonina, S. N.

    2016-02-01

    Transformation of zero-order Bessel beams into a second-order vortex beam in the process of propagation in a c-cut of CaCO3 and LiNbO3 crystals has been investigated experimentally. The possibility of controlling beam transformation by means of changing the wavefront curvature of the illuminating beam is shown. Aperiodic transformation of a Bessel beam by illumination of diffractive axicon with convergent light is noted.

  9. Elimination of inrush current of transformers and distribution lines

    SciTech Connect

    Asghar, M.S.J.

    1995-12-31

    Repeated switching of distribution transformers take place due to poor generation and load shading. The transformer mounted on electric locomotive is also regularly reswitched after crossing each buffer zone between two substations. The steady-state magnetizing current of a transformer is about 5% of the full load current.But the transient inrush current may be as high as ten times the full-load current. The switching instant decides the nature and magnitude of the switching current and it is used here to control the inrush current. Another method is adopted by placing a capacitor at the secondary side of the unloaded transformer connected at the sending or receiving end of the distribution line. Third method is proposed using the distribution line as a low-pass filter. In case of a three-phase transformer, when it is switched, inrush current flows in either one or two phase windings. Instead of a simultaneous switching of all the phases (windings), each winding of transformer is switched at predetermined switching instants sequentially. Thus inrush currents are contained to steady-state level using an instant-controlled switching circuit. Switching of all phases completes within 1/3 or 1/4 of the power-cycle depending upon the mode of transformer configuration and the switching strategy. The switching current is found same as the steady-state no-load current. These schemes are useful for traction transformer as well as for poorly supplied and poorly maintained distribution lines including traction line which are subjected to repeated switching.

  10. A Superconducting transformer system for high current cable testing

    SciTech Connect

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

    2010-02-15

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

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

    PubMed

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

    2010-03-01

    This article describes the development of a direct-current (dc) superconducting transformer system for the high current test of superconducting cables. The transformer consists of a core-free 10,464 turn primary solenoid which is enclosed by a 6.5 turn secondary. The transformer is designed to deliver a 50 kA dc secondary current at a dc primary current of about 50 A. The secondary current is measured inductively using two toroidal-wound Rogowski coils. The Rogowski coil signal is digitally integrated, resulting in a voltage signal that is proportional to the secondary current. This voltage signal is used to control the secondary current using a feedback loop which automatically compensates for resistive losses in the splices to the superconducting cable samples that are connected to the secondary. The system has been commissioned up to 28 kA secondary current. The reproducibility in the secondary current measurement is better than 0.05% for the relevant current range up to 25 kA. The drift in the secondary current, which results from drift in the digital integrator, is estimated to be below 0.5 A/min. The system's performance is further demonstrated through a voltage-current measurement on a superconducting cable sample at 11 T background magnetic field. The superconducting transformer system enables fast, high resolution, economic, and safe tests of the critical current of superconducting cable samples. PMID:20370213

  12. Laser diagnostic for high current H{sup {minus}} beams

    SciTech Connect

    Shafer, R.E.

    1998-05-05

    In the last 5 years, significant technology advances have been made in the performance, size, and cost of solid-state diode-pumped lasers. These developments enable the use of compact Q-switched Nd:YAG lasers as a beam diagnostic for high current H{sup {minus}} beams. Because the threshold for photodetachment is only 0.75 eV, and the maximum detachment cross section is 4 {times} 10{sup {minus}17} cm{sup 2} at 1.5 eV, a 50 mJ/pulse Q-switched Nd:YAG laser can neutralize a significant fraction of the beam in a single 10-ns wide pulse. The neutral beam maintains nearly identical parameters as the parent H{sup {minus}} beam, including size, divergence, energy, energy spread, and phase spread. A dipole magnet can separate the neutral beam from the H{sup {minus}} beam to allow diagnostics on the neutral beam without intercepting the high-current H{sup {minus}} beam. Such a laser system can also be used to extract a low current proton beam, or to induce fluorescence in partially stripped heavy ion beams. Possible beamline diagnostic systems will be reviewed, and the neutral beam yields will be calculated.

  13. Damage Identification in Beam Structure using Spatial Continuous Wavelet Transform

    NASA Astrophysics Data System (ADS)

    Janeliukstis, R.; Rucevskis, S.; Wesolowski, M.; Kovalovs, A.; Chate, A.

    2015-11-01

    In this paper the applicability of spatial continuous wavelet transform (CWT) technique for damage identification in the beam structure is analyzed by application of different types of wavelet functions and scaling factors. The proposed method uses exclusively mode shape data from the damaged structure. To examine limitations of the method and to ascertain its sensitivity to noisy experimental data, several sets of simulated data are analyzed. Simulated test cases include numerical mode shapes corrupted by different levels of random noise as well as mode shapes with different number of measurement points used for wavelet transform. A broad comparison of ability of different wavelet functions to detect and locate damage in beam structure is given. Effectiveness and robustness of the proposed algorithms are demonstrated experimentally on two aluminum beams containing single mill-cut damage. The modal frequencies and the corresponding mode shapes are obtained via finite element models for numerical simulations and by using a scanning laser vibrometer with PZT actuator as vibration excitation source for the experimental study.

  14. Modeling of explosive electron emission and electron beam dynamics in high-current devices

    NASA Astrophysics Data System (ADS)

    Anishchenko, S. V.; Gurinovich, A. A.

    2014-03-01

    Based on a detailed analysis of explosive electron emission in high-current electronic devices, we formulate a system of equations that describes the expansion of the cathode plasma and the generation of high-current electron beams. The system underlies the numerical algorithm for the hybrid code which enables simulating the charged particles' dynamics in high-current vircators with open resonators. Using the Gabor-Morlet transform, we perform the time-frequency analysis of vircator radiation.

  15. Gaussian laser beam transformation into an optical vortex beam by helical lens

    NASA Astrophysics Data System (ADS)

    Janicijevic, Ljiljana; Topuzoski, Suzana

    2016-01-01

    In this article, we investigate the Fresnel diffraction characteristics of the hybrid optical element which is a combination of a spiral phase plate (SPP) with topological charge p and a thin lens with focal length f, named the helical lens (HL). As incident a Gaussian laser beam is treated, having its waist a distance ζ from the HL plane and its axis passing through the centre of the HL. It is shown that the SPP introduces a phase singularity of pth order to the incident beam, while the lens transforms the beam characteristic parameters. The output light beam is analyzed in detail: its characteristic parameters and focusing properties, amplitude and intensity distributions and the vortex rings profiles, and radii, at any z distance behind the HL plane, as well as in the near and far field.

  16. Single beam Fourier transform digital holographic quantitative phase microscopy

    SciTech Connect

    Anand, A. Chhaniwal, V. K.; Mahajan, S.; Trivedi, V.; Faridian, A.; Pedrini, G.; Osten, W.; Dubey, S. K.; Javidi, B.

    2014-03-10

    Quantitative phase contrast microscopy reveals thickness or height information of a biological or technical micro-object under investigation. The information obtained from this process provides a means to study their dynamics. Digital holographic (DH) microscopy is one of the most used, state of the art single-shot quantitative techniques for three dimensional imaging of living cells. Conventional off axis DH microscopy directly provides phase contrast images of the objects. However, this process requires two separate beams and their ratio adjustment for high contrast interference fringes. Also the use of two separate beams may make the system more vulnerable to vibrations. Single beam techniques can overcome these hurdles while remaining compact as well. Here, we describe the development of a single beam DH microscope providing whole field imaging of micro-objects. A hologram of the magnified object projected on to a diffuser co-located with a pinhole is recorded with the use of a commercially available diode laser and an arrayed sensor. A Fourier transform of the recorded hologram directly yields the complex amplitude at the image plane. The method proposed was investigated using various phase objects. It was also used to image the dynamics of human red blood cells in which sub-micrometer level thickness variation were measurable.

  17. Wave Transformation and Breaking on a Sheared Current

    NASA Astrophysics Data System (ADS)

    Zippel, S.; Thomson, J. M.; Rusch, C.

    2014-12-01

    Waves shoaling against tidal currents at river inlets have long been a hazard to navigation. We present measurements of waves, currents, and turbulence from SWIFT drifters at the Columbia River Mouth to diagnose wave transformation, breaking, and the resulting turbulence. In particular, down-looking velocity profiles, measured onboard the drifters, allow for evaluation of wave transformation on a vertically sheared current, for which theory exists but few in situ measurements are available. One consequence of wave transformation is steepening and breaking, which is identified using visual images, increased near surface turbulence, and gradients in wave energy flux. Vertical turbulent dissipation profiles measured during breaking are compared to existing scalings developed for deep and shallow water and expanded to the intermediate depth conditions common at the Columbia River Mouth. The analysis is intended to improve hydrodynamic models, especially two-way coupled wave-current models, and to aid navigation by better predicting dangerous wave conditions.

  18. Electrical measurement techniques for pulsed high current electron beams

    SciTech Connect

    Struve, K.W.

    1986-04-01

    The advent of high current (1 to 100 kA), moderate energy (>10 MeV), short pulse (1 to 100 ns) electron accelerators used for charged particle beam research has motivated a need to complement standard diagnostics with development of new diagnostic techniques to measure electron beam parameters. A brief survey is given of the diagnostics for measuring beam current, position, size, energy, and emittance. While a broad scope of diagnostics will be discussed, this survey will emphasize diagnostics used on the Experimental Test Accelerator (ETA) and Advanced Test Accelerator (ATA). Focus is placed on diagnostics measuring beam current, position and size. Among the diagnostics discussed are resistive wall current monitors, B/sub theta/ loops, Rogowski coils, Faraday cups, and x-ray wire diagnostics. Operation at higher current levels also increases radiation and electromagnetic pulse interference. These difficulties and methods for circumventing them are also discussed.

  19. Limiting current of intense electron beams in a decelerating gap

    NASA Astrophysics Data System (ADS)

    Nusinovich, G. S.; Beaudoin, B. L.; Thompson, C.; Karakkad, J. A.; Antonsen, T. M.

    2016-02-01

    For numerous applications, it is desirable to develop electron beam driven efficient sources of electromagnetic radiation that are capable of producing the required power at beam voltages as low as possible. This trend is limited by space charge effects that cause the reduction of electron kinetic energy and can lead to electron reflection. So far, this effect was analyzed for intense beams propagating in uniform metallic pipes. In the present study, the limiting currents of intense electron beams are analyzed for the case of beam propagation in the tubes with gaps. A general treatment is illustrated by an example evaluating the limiting current in a high-power, tunable 1-10 MHz inductive output tube (IOT), which is currently under development for ionospheric modification. Results of the analytical theory are compared to results of numerical simulations. The results obtained allow one to estimate the interaction efficiency of IOTs.

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

    SciTech Connect

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

    2009-09-20

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

  1. Current Technologies and Related Issues for Mushroom Transformation

    PubMed Central

    Kim, Sinil; Ha, Byeong-Suk

    2015-01-01

    Mushroom transformation requires a series of experimental steps, including generation of host strains with a desirable selective marker, design of vector DNA, removal of host cell wall, introduction of foreign DNA across the cell membrane, and integration into host genomic DNA or maintenance of an autonomous vector DNA inside the host cell. This review introduces limitations and obstacles related to transformation technologies along with possible solutions. Current methods for cell wall removal and cell membrane permeabilization are summarized together with details of two popular technologies, Agrobacterium tumefaciens-mediated transformation and restriction enzyme-mediated integration. PMID:25892908

  2. Transformer coupling for transmitting direct current through a barrier

    DOEpatents

    Brown, R.L.; Guilford, R.P.; Stichman, J.H.

    1987-06-29

    The transmission system for transmitting direct current from an energy source on one side of an electrical and mechanical barrier to a load on the other side of the barrier utilizes a transformer comprising a primary core on one side of the transformer and a secondary core on the other side of the transformer. The cores are magnetically coupled selectively by moving a magnetic ferrite coupler in and out of alignment with the poles of the cores. The direct current from the energy source is converted to a time varying current by an oscillating circuit, which oscillating circuit is optically coupled to a secondary winding on the secondary core to interrupt oscillations upon the voltage in the secondary winding exceeding a preselected level. 4 figs.

  3. Transformer coupling for transmitting direct current through a barrier

    DOEpatents

    Brown, Ralph L.; Guilford, Richard P.; Stichman, John H.

    1988-01-01

    The transmission system for transmitting direct current from an energy source on one side of an electrical and mechanical barrier to a load on the other side of the barrier utilizes a transformer comprising a primary core on one side of the transformer and a secondary core on the other side of the transformer. The cores are magnetically coupled selectively by moving a magnetic ferrite coupler in and out of alignment with the poles of the cores. The direct current from the energy source is converted to a time varying current by an oscillating circuit, which oscillating circuit is optically coupled to a secondary winding on the secondary core to interrupt oscillations upon the voltage in the secondary winding exceeding a preselected level.

  4. Dynamics of a high-current relativistic electron beam

    SciTech Connect

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

    2015-06-15

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

  5. Low Impedance Bellows for High-current Beam Operations

    SciTech Connect

    Wu, G; Nassiri, A; Waldschmidt, G J; Yang, Y; Feingold, J J; Mammosser, J D; Rimmer, R A; Wang, H; Jang, J; Kim, S H

    2012-07-01

    In particle accelerators, bellows are commonly used to connect beamline components. Such bellows are traditionally shielded to lower the beam impedance. Excessive beam impedance can cause overheating in the bellows, especially in high beam current operation. For an SRF-based accelerator, the bellows must also be particulate free. Many designs of shielded bellows incorporate rf slides or fingers that prevent convolutions from being exposed to wakefields. Unfortunately these mechanical structures tend to generate particulates that, if left in the SRF accelerator, can migrate into superconducting cavities, the accelerator's critical components. In this paper, we describe a prototype unshielded bellows that has low beam impedance and no risk of particulate generation.

  6. Method for measuring and controlling beam current in ion beam processing

    DOEpatents

    Kearney, Patrick A.; Burkhart, Scott C.

    2003-04-29

    A method for producing film thickness control of ion beam sputter deposition films. Great improvements in film thickness control is accomplished by keeping the total current supplied to both the beam and suppressor grids of a radio frequency (RF) in beam source constant, rather than just the current supplied to the beam grid. By controlling both currents, using this method, deposition rates are more stable, and this allows the deposition of layers with extremely well controlled thicknesses to about 0.1%. The method is carried out by calculating deposition rates based on the total of the suppressor and beam currents and maintaining the total current constant by adjusting RF power which gives more consistent values.

  7. Laser diagnostic for high current H{sup {minus}} beams

    SciTech Connect

    Shafer, R.E.

    1998-01-01

    Laser photodetachment can be used on high current, high energy H{sup {minus}} beams to carry out a wide variety of beam diagnostic measurements parasitically during normal operation, without having to operate the facility at either reduced current or duty cycle. Suitable Q-switched laser systems are small, inexpensive, and can be mounted on or near the beamline. Most of the proposed laser-based diagnostics techniques have already been demonstrated.

  8. DEVELOPMENT OF ACCELERATOR DATA REPORTING SYSTEM AND ITS APPLICATION TO TREND ANALYSIS OF BEAM CURRENT DATA

    SciTech Connect

    Padilla, M.J.; Blokland, W.

    2009-01-01

    Detailed ongoing information about the ion beam quality is crucial to the successful operation of the Spallation Neutron Source at Oak Ridge National Laboratory. In order to provide the highest possible neutron production time, ion beam quality is monitored to isolate possible problems or performance-related issues throughout the accelerator and accumulator ring. For example, beam current monitor (BCM) data is used to determine the quality of the beam transport through the accelerator. In this study, a reporting system infrastructure was implemented and used to generate a trend analysis report of the BCM data. The BCM data was analyzed to facilitate the identifi cation of monitor calibration issues, beam trends, beam abnormalities, beam deviations and overall beam quality. A comparison between transformed BCM report data and accelerator log entries shows promising results which represent correlations between the data and changes made within the accelerator. The BCM analysis report is one of many reports within a system that assist in providing overall beam quality information to facilitate successful beam operation. In future reports, additional data manipulation functions and analysis can be implemented and applied. Built-in and user-defi ned analytic functions are available throughout the reporting system and can be reused with new data.

  9. Cumulative Beam Breakup in Linear Accelerators with Arbitrary Beam Current Profile

    SciTech Connect

    Jean Delayen

    2003-06-01

    An analytical formalism for the solution of cumulative beam breakup in linear accelerators with arbitrary time dependence of beam current is presented, and a closed-form expression for the time and position dependence of the transverse displacement is obtained. It is applied to the behavior of single bunches and to the steady state and transient behavior of dc beams and beams composed of point-like and finite length bunches. This formalism is also applied to the problem of cumulative beam breakup in the presence of random displacement of cavities and focusing elements, and a general solution is presented.

  10. Current Correlations in a Majorana Beam Splitter

    NASA Astrophysics Data System (ADS)

    Haim, Arbel; Berg, Erez; von Oppen, Felix; Oreg, Yuval

    We study current correlations in a T-junction composed of a grounded topological superconductor and of two normal-metal leads which are biased at a voltage V. We show that the existence of an isolated Majorana zero mode in the junction dictates a universal behavior for the cross correlation of the currents through the two normal-metal leads of the junction. The cross correlation is negative and approaches zero at high bias voltages as - 1 / V . This behavior is robust in the presence of disorder and multiple transverse channels, and persists at finite temperatures. In contrast, an accidental low-energy Andreev bound state gives rise to non-universal behavior of the cross correlation. We employ numerical transport simulations to corroborate our conclusions.

  11. Current correlations in a Majorana beam splitter

    NASA Astrophysics Data System (ADS)

    Haim, Arbel; Berg, Erez; von Oppen, Felix; Oreg, Yuval

    2015-12-01

    We study current correlations in a T junction composed of a grounded topological superconductor and of two normal-metal leads which are biased at a voltage V . We show that the existence of an isolated Majorana zero mode in the junction dictates a universal behavior for the cross correlation of the currents through the two normal-metal leads of the junction. The cross correlation is negative and approaches zero at high bias voltages as -1 /V . This behavior is robust in the presence of disorder and multiple transverse channels, and persists at finite temperatures. In contrast, an accidental low-energy Andreev bound state gives rise to nonuniversal behavior of the cross correlation. We employ numerical transport simulations to corroborate our conclusions.

  12. A determination of the current density in electron beams

    NASA Technical Reports Server (NTRS)

    Beil, R. J.

    1982-01-01

    Current gathering rotating probe techniques were used to examine the envelope shape and power density profile of electron beams used in electron beam welding devices. The electron power density contours which determine the shape of the weld vapor cavity, penetration, and local heat distribution were considered. A mathematical analysis consistent with a rotating probe technique necessary to determine the current density distribution (assumed symmetrically radial) in a cross-section of the beam is provided. An explanation of the experimental technique for obtaining data, a BASIC language computer program to determine the current density from the data, and a study indicating the level of confidence to be associated with results obtained are also provided. An example of the application of the analysis to some experimental electron beam data is included.

  13. Photoacoustic transformation of Bessel light beams in magnetoactive superlattices

    SciTech Connect

    Mityurich, G. S.; Chernenok, E. V.; Sviridova, V. V.; Serdyukov, A. N.

    2015-03-15

    Photoacoustic transformation of the TE mode of a Bessel light beam (BLB) has been studied for piezoelectric detection in short-period superlattices formed by magnetoactive crystals of bismuth germanate (Bi{sub 12}GeO{sub 20}) and bismuth silicate (Bi{sub 12}SiO{sub 20}) types. It is shown that the resulting signal amplitude can be controlled using optical schemes of BLB formation with a tunable cone angle. A resonant increase in the signal amplitude has been found in the megahertz range of modulation frequencies and its dependences on the BLB modulation frequency, geometric sizes of the two-layer structure and piezoelectric transducer, radial coordinate of the polarization BLB mode, and dissipative superlattice parameters are analyzed.

  14. Conceptual design of a beam steering lens through transformation electromagnetics.

    PubMed

    Yi, Jianjia; Burokur, Shah Nawaz; de Lustrac, André

    2015-05-18

    In this paper, based on transformation electromagnetics, the design procedure of a lens antenna, which steers the radiated beam of a patch array, is presented. Laplace's equation is adopted to construct the mapping between the virtual space and the physical space. The two dimensional (2D) design method can be extended to a potential three-dimensional (3D) realization, and with a proper parameter simplification, the lens can be further realized by common metamaterials or isotropic graded refractive index (GRIN) materials. Full wave simulations are performed to validate the proposed concept. It is observed that by placing the lens on a feeding source, we are able to steer the radiation emitted by the latter source. PMID:26074547

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

    SciTech Connect

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

    1994-11-01

    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.

  16. The backward phase flow and FBI-transform-based Eulerian Gaussian beams for the Schroedinger equation

    SciTech Connect

    Leung Shingyu; Qian Jianliang

    2010-11-20

    We propose the backward phase flow method to implement the Fourier-Bros-Iagolnitzer (FBI)-transform-based Eulerian Gaussian beam method for solving the Schroedinger equation in the semi-classical regime. The idea of Eulerian Gaussian beams has been first proposed in . In this paper we aim at two crucial computational issues of the Eulerian Gaussian beam method: how to carry out long-time beam propagation and how to compute beam ingredients rapidly in phase space. By virtue of the FBI transform, we address the first issue by introducing the reinitialization strategy into the Eulerian Gaussian beam framework. Essentially we reinitialize beam propagation by applying the FBI transform to wavefields at intermediate time steps when the beams become too wide. To address the second issue, inspired by the original phase flow method, we propose the backward phase flow method which allows us to compute beam ingredients rapidly. Numerical examples demonstrate the efficiency and accuracy of the proposed algorithms.

  17. Amplification of S-1 Spheromak current by an inductive current transformer

    SciTech Connect

    Jardin, S.C.; Janos, A.; Yamada, M.

    1985-11-01

    We attempt to predict the consequences of adding an inductive current transformer (OH Transformer) to the present S-1 Spheromak experiment. Axisymmetric modeling with only classical dissipation shows an increase of toroidal current and a shrinking and hollowing of the current channel, conserving toroidal flux. These unstable profiles will undergo helical reconnection, conserving helicity K = ..integral.. A-vector x B-vector d tau while increasing the toroidal flux and decreasing the poloidal flux so that the plasma relaxes toward the Taylor state. This flux rearrangement is modeled by a new current viscosity term in the mean-field Ohm's law which conserves helicity and dissipates energy.

  18. Space charge templates for high-current beam modeling

    SciTech Connect

    Vorobiev, Leonid G.; /Fermilab

    2008-07-01

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

  19. Profile, Current, and Halo Monitors of the PROSCAN Beam Lines

    SciTech Connect

    Doelling, Rudolf

    2004-11-10

    PROSCAN, an extended medical facility using proton beams for the treatment of deep-seated tumors and eye melanoma, is under construction at PSI. Ionization chambers and secondary emission monitors will be used as current monitors and in a multi-strip configuration as profile monitors at the PROSCAN beam lines. A thin and a thick version of these detectors are in preparation as well as a 4-segment ionization chamber to detect the beam halo. Electromagnetic and microphonic noise from the signal and high-voltage cables, saturation due to recombination, and the evaluation of the profiles are discussed, as well as measures to detect failures of the detectors during operation.

  20. Current limiting mechanisms in electron and ion beam experiments

    NASA Technical Reports Server (NTRS)

    Olsen, R. C.

    1990-01-01

    The emission and collection of current from satellites or rockets in the ionosphere is a process which, at equilibrium, requires a balance between inward and outward currents. In most active experiments in the ionosphere and magnetosphere, the emitted current exceeds the integrated thermal current by one or more orders of magnitude. The system response is typically for the emitted current to be limited by processes such as differential charging of insulating surfaces, interactions between an emitted beam and the local plasma, and interactions between the beam and local neutral gas. These current limiting mechanisms have been illustrated for 20 years in sounding rocket and satellite experiments, which are reviewed here. Detailed presentations of the Spacecraft Charging at High Altitude (SCATHA) electron and ion gun experiments are used to demonstrate the general range of observed phenomena.

  1. Focusing of high-current laser-driven ion beams

    NASA Astrophysics Data System (ADS)

    Badziak, J.; Jabłoński, S.

    2007-04-01

    Using a two-dimensional relativistic hydrodynamic code, it is shown that a dense high-current ion beam driven by a short-pulse laser can be effectively focused by curving the target front surface. The focused beam parameters essentially depend on the density gradient scale length of the preplasma Ln and the surface curvature radius RT. When Ln⩽0.5λL (λL is the laser wavelength) and RT is comparable with the laser beam aperture dL, a significant fraction of the accelerated ions is focused on a spot much smaller than dL, which results in a considerable increase in the ion fluence and current density. Using high-contrast multipetawatt picosecond laser pulses of relativistic intensity (˜1020W/cm2), focused ion (proton) current densities approaching those required for fast ignition of DT fuel seem to be feasible.

  2. Plasma Charge Current for Controlling and Monitoring Electron Beam Welding with Beam Oscillation

    PubMed Central

    Trushnikov, Dmitriy; Belenkiy, Vladimir; Shchavlev, Valeriy; Piskunov, Anatoliy; Abdullin, Aleksandr; Mladenov, Georgy

    2012-01-01

    Electron beam welding (EBW) shows certain problems with the control of focus regime. The electron beam focus can be controlled in electron-beam welding based on the parameters of a secondary signal. In this case, the parameters like secondary emissions and focus coil current have extreme relationships. There are two values of focus coil current which provide equal value signal parameters. Therefore, adaptive systems of electron beam focus control use low-frequency scanning of focus, which substantially limits the operation speed of these systems and has a negative effect on weld joint quality. The purpose of this study is to develop a method for operational control of the electron beam focus during welding in the deep penetration mode. The method uses the plasma charge current signal as an additional informational parameter. This parameter allows identification of the electron beam focus regime in electron-beam welding without application of additional low-frequency scanning of focus. It can be used for working out operational electron beam control methods focusing exactly on the welding. In addition, use of this parameter allows one to observe the shape of the keyhole during the welding process. PMID:23242276

  3. Plasma charge current for controlling and monitoring electron beam welding with beam oscillation.

    PubMed

    Trushnikov, Dmitriy; Belenkiy, Vladimir; Shchavlev, Valeriy; Piskunov, Anatoliy; Abdullin, Aleksandr; Mladenov, Georgy

    2012-01-01

    Electron beam welding (EBW) shows certain problems with the control of focus regime. The electron beam focus can be controlled in electron-beam welding based on the parameters of a secondary signal. In this case, the parameters like secondary emissions and focus coil current have extreme relationships. There are two values of focus coil current which provide equal value signal parameters. Therefore, adaptive systems of electron beam focus control use low-frequency scanning of focus, which substantially limits the operation speed of these systems and has a negative effect on weld joint quality. The purpose of this study is to develop a method for operational control of the electron beam focus during welding in the deep penetration mode. The method uses the plasma charge current signal as an additional informational parameter. This parameter allows identification of the electron beam focus regime in electron-beam welding without application of additional low-frequency scanning of focus. It can be used for working out operational electron beam control methods focusing exactly on the welding. In addition, use of this parameter allows one to observe the shape of the keyhole during the welding process. PMID:23242276

  4. Propagation properties of Bessel and Bessel-Gaussian beams in a fractional Fourier transform optical system

    NASA Astrophysics Data System (ADS)

    Zhao, Chengliang; Huang, Kaikai; Lu, Xuanhui

    2010-03-01

    The properties of Bessel-Gaussian beams (BGBs) and Bessel beams (BBs) propagating through a fractional Fourier transform (FRT) optical system have been investigated. The analytical transformation formulae for BBs and BGBs propagation through a FRT optical system are derived based on definition of the FRT in the cylindrical coordinate system. By using the derived formula, numerical examples are illustrated.

  5. An accurate continuous calibration system for high voltage current transformer

    SciTech Connect

    Tong Yue; Li Binhong

    2011-02-15

    A continuous calibration system for high voltage current transformers is presented in this paper. The sensor of this system is based on a kind of electronic instrument current transformer, which is a clamp-shape air core coil. This system uses an optical fiber transmission system for its signal transmission and power supply. Finally the digital integrator and fourth-order convolution window algorithm as error calculation methods are realized by the virtual instrument with a personal computer. It is found that this system can calibrate a high voltage current transformer while energized, which means avoiding a long calibrating period in the power system and the loss of power metering expense. At the same time, it has a wide dynamic range and frequency band, and it can achieve a high accuracy measurement in a complex electromagnetic field environment. The experimental results and the on-site operation results presented in the last part of the paper, prove that it can reach the 0.05 accuracy class and is easy to operate on site.

  6. An accurate continuous calibration system for high voltage current transformer.

    PubMed

    Tong, Yue; Li, Bin Hong

    2011-02-01

    A continuous calibration system for high voltage current transformers is presented in this paper. The sensor of this system is based on a kind of electronic instrument current transformer, which is a clamp-shape air core coil. This system uses an optical fiber transmission system for its signal transmission and power supply. Finally the digital integrator and fourth-order convolution window algorithm as error calculation methods are realized by the virtual instrument with a personal computer. It is found that this system can calibrate a high voltage current transformer while energized, which means avoiding a long calibrating period in the power system and the loss of power metering expense. At the same time, it has a wide dynamic range and frequency band, and it can achieve a high accuracy measurement in a complex electromagnetic field environment. The experimental results and the on-site operation results presented in the last part of the paper, prove that it can reach the 0.05 accuracy class and is easy to operate on site. PMID:21361633

  7. DPSS Laser Beam Quality Optimization Through Pump Current Tuning

    SciTech Connect

    Omohundro, Rob; Callen, Alice; Sukuta, Sydney; /San Jose City Coll.

    2012-03-30

    The goal of this study is to demonstrate how a DPSS laser beam's quality parameters can be simultaneously optimized through pump current tuning. Two DPSS lasers of the same make and model were used where the laser diode pump current was first varied to ascertain the lowest RMS noise region. The lowest noise was found to be 0.13% in this region and the best M{sup 2} value of 1.0 and highest laser output power were simultaneously attained at the same current point. The laser manufacturer reported a M{sup 2} value of 1.3 and RMS noise value of .14% for these lasers. This study therefore demonstrates that pump current tuning a DPSS laser can simultaneously optimize RMS Noise, Power and M{sup 2} values. Future studies will strive to broaden the scope of the beam quality parameters impacted by current tuning.

  8. A neutron diagnostic for high current deuterium beams

    SciTech Connect

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

    2012-02-15

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

  9. Discrimination of orbital angular momentum modes of the terahertz vortex beam using a diffractive mode transformer.

    PubMed

    Liu, Changming; Wei, Xuli; Niu, Liting; Wang, Kejia; Yang, Zhengang; Liu, Jinsong

    2016-06-13

    We present an efficient method to discriminate orbital angular momentum (OAM) of the terahertz (THz) vortex beam using a diffractive mode transformer. The mode transformer performs a log-polar coordinate transformation of the input THz vortex beam, which consists of two 3D-printed diffractive elements. A following lens separates each transformed OAM mode to a different lateral position in its focal plane. This method enables a simultaneous measurement over multiple OAM modes of the THz vortex beam. We experimentally demonstrate the measurement of seven individual OAM modes and two multiplexed OAM modes, which is in good agreement with simulations. PMID:27410274

  10. Return Current Electron Beams and Their Generation of "Raman" Scattering

    NASA Astrophysics Data System (ADS)

    Simon, A.

    1998-11-01

    For some years, we(A. Simon and R. W. Short, Phys. Rev. Lett. 53), 1912 (1984). have proposed that the only reasonable explanation for many of the observations of "Raman" scattering is the presence of an electron beam in the plasma. (The beam creates a bump-on-tail instability.) Two major objections to this picture have been observation of Raman when no n_c/4 surface was present, with no likely source for the electron beam, and the necessity for the initially outward directed beam to bounce once to create the proper waves. Now new observations on LLE's OMEGA(R. Petrasso et al), this conference. and at LULI(C. Labaune et al)., Phys. Plasma 5, 234 (1998). have suggested a new origin for the electron beam. This new scenario answers the previous objections, maintains electron beams as the explanation of the older experiments, and may clear up puzzling observations that have remained unexplained. The new scenario is based on two assumptions: (1) High positive potentials develop in target plasmas during their creation. (2) A high-intensity laser beam initiates spark discharges from nearby surfaces to the target plasma. The resulting return current of electrons should be much more delta-like, is initially inwardly directed, and no longer requires the continued presence of a n_c/4 surface. Scattering of the interaction beam from the BOT waves yields the observed Raman signal. Experimental observations that support this picture will be cited. ``Pulsation'' of the scattering and broadband ``flashes'' are a natural part of this scenario. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460.

  11. Electron beam current in high power cylindrical diode

    SciTech Connect

    Roy, Amitava; Menon, R.; Mitra, S.; Sharma, Vishnu; Singh, S. K.; Nagesh, K. V.; Chakravarthy, D. P.

    2010-01-15

    Intense electron beam generation studies were carried out in high power cylindrical diode to investigate the effect of the accelerating gap and diode voltage on the electron beam current. The diode voltage has been varied from 130 to 356 kV, whereas the current density has been varied from 87 to 391 A/cm{sup 2} with 100 ns pulse duration. The experimentally obtained electron beam current in the cylindrical diode has been compared with the Langmuir-Blodgett law. It was found that the diode current can be explained by a model of anode and cathode plasma expanding toward each other. However, the diode voltage and current do not follow the bipolar space-charge limited flow model. It was also found that initially only a part of the cathode take part in the emission process. The plasma expands at 4.2 cm/mus for 1.7 cm anode-cathode gap and the plasma velocity decreases for smaller gaps. The electrode plasma expansion velocity of the cylindrical diode is much smaller as compared with the planar diode for the same accelerating gap and diode voltage. Therefore, much higher voltage can be obtained for the cylindrical diodes as compared with the planar diodes for the same accelerating gap.

  12. Beam Dynamics Aspects of High Current Beams in a Superconducting Proton Linac

    NASA Astrophysics Data System (ADS)

    Bellomo, Giovanni; Pagani, Carlo; Pierini, Paolo

    1997-05-01

    High current CW proton linac accelerators have been recently proposed for nuclear waste transmutation and concurrent energy production. In most of the designs the high energy part (100 MeV up to 1-2 GeV) of the linac employs low frequency superconducting structures (352-700 MHz). Here we present beam dynamics issues for the high current (10-50 mA) beams in the superconducting section of such an accelerator, based on 352 MHz β-graded, LEP style cavities, as proposed at Linac 96(C. Pagani, G. Bellomo, P. Pierini, ``A High Current Proton Linac with 352 MHz SC Cavities'', Proceedings of the XVIII Int. Linear Acc. Conf., eds. C. Hill, M. Vretenar, CERN 96-07, 15 November 1996). In particular, smooth beam propagation along the linac has been reached with decreasing phase advances along the linac, and the design has been updated to match the beam dynamics results. Mismatching oscillations are discussed, as they are considered to cause beam halo and, consequently, beam losses.

  13. Innovative real-time and non-destructive method of beam profile measurement under large beam current irradiation for BNCT

    NASA Astrophysics Data System (ADS)

    Takada, M.; Kamada, S.; Suda, M.; Fujii, R.; Nakamura, M.; Hoshi, M.; Sato, H.; Endo, S.; Hamano, T.; Arai, S.; Higashimata, A.

    2012-10-01

    We developed a real-time and non-destructive method of beam profile measurement on a target under large beam current irradiation, and without any complex radiation detectors or electrical circuits. We measured the beam profiles on a target by observing the target temperature using an infrared-radiation thermometer camera. The target temperatures were increased and decreased quickly by starting and stopping the beam irradiation within 1 s in response speed. Our method could trace beam movements rapidly. The beam size and position were calibrated by measuring O-ring heat on the target. Our method has the potential to measure beam profiles at beam current over 1 mA for proton and deuteron with the energy around 3 MeV and allows accelerator operators to adjust the beam location during beam irradiation experiments without decreasing the beam current.

  14. Energy loss due to eddy current in linear transformer driver cores

    NASA Astrophysics Data System (ADS)

    Kim, A. A.; Mazarakis, M. G.; Manylov, V. I.; Vizir, V. A.; Stygar, W. A.

    2010-07-01

    In linear transformer drivers [Phys. Rev. ST Accel. Beams 12, 050402 (2009)PRABFM1098-440210.1103/PhysRevSTAB.12.050402; Phys. Rev. ST Accel. Beams 12, 050401 (2009)PRABFM1098-440210.1103/PhysRevSTAB.12.050401] as well as any other linear induction accelerator cavities, ferromagnetic cores are used to prevent the current from flowing along the induction cavity walls which are in parallel with the load. But if the core is made of conductive material, the applied voltage pulse generates the eddy current in the core itself which heats the core and therefore also reduces the overall linear transformer driver (LTD) efficiency. The energy loss due to generation of the eddy current in the cores depends on the specific resistivity of the core material, the design of the core, as well as on the distribution of the eddy current in the core tape during the remagnetizing process. In this paper we investigate how the eddy current is distributed in a core tape with an arbitrary shape hysteresis loop. Our model is based on the textbook knowledge related to the eddy current generation in ferromagnetics with rectangular hysteresis loop, and in usual conductors. For the reader’s convenience, we reproduce some most important details of this knowledge in our paper. The model predicts that the same core would behave differently depending on how fast the applied voltage pulse is: in the high frequency limit, the equivalent resistance of the core reduces during the pulse whereas in the low frequency limit it is constant. An important inference is that the energy loss due to the eddy current generation can be reduced by increasing the cross section of the core over the minimum value which is required to avoid its saturation. The conclusions of the model are confirmed with experimental observations presented at the end of the paper.

  15. Bessel beam transformation in c-cuts of uniaxial crystals by varying the source wavelength

    NASA Astrophysics Data System (ADS)

    Paranin, V. D.

    2016-04-01

    Transformation of Bessel beam of a zero order to Bessel beam of the second order in c-cut of CaCO3 crystal is experimentally investigated. Possibility of output beam control at changing of wavelength and using of a diffraction axicon is shown. Full transformation of beams at changing of wavelength Δλ=1.5 nanometers is received at initial wavelength λ=637.5 nanometers for a crystal of CaCO3 with 15 mm long and a diffraction axicon with period of 2 microns. The theoretical value of necessary wavelength changing is Δλ=1.7 nanometers that is according with experimental results.

  16. A review of high beam current RFQ accelerators and funnels

    SciTech Connect

    Schneider, J.D.

    1998-12-01

    The authors review the design features of several high-current (> 20-mA) and high-power (> 1-mA average) proton or H{sup {minus}} injectors, RFQs, and funnels. They include a summary of observed performance and will mention a sampling of new designs, including the proposed incorporation of beam choppers. Different programs and organizations have chosen to build the RFQ in diverse configurations. Although the majority of RFQs are either low-current or very low duty-factor, several versions have included high-current and/or high-power designs for either protons or H{sup {minus}} ions. The challenges of cooling, handling high space-charge forces, and coupling with injectors and subsequent accelerators are significant. In all instances, beam tests were a valuable learning experience, because not always did these as-built structures perform exactly as predicted by the earlier design codes. They summarize the key operational parameters, indicate what was achieved, and highlight what was learned in these tests. Based on this generally good performance and high promise, even more challenging designs are being considered for new applications that include even higher powers, beam funnels and choppers.

  17. Beam position and total current monitor for heavy ion fusion beams

    SciTech Connect

    Berners, D.; Reginato, L.L.

    1992-10-01

    Heavy Ion Fusion requires moderate currents, 1-10A, for a duration of about 1 {mu}s. For accurate beam transport, the center of charge must be located to within {plus_minus} 100 {mu}m. Beam position and intensity may be excited at frequencies approaching 10 MHz, and the monitoring system must have adequate bandwidth to respond at these frequencies. We have modified the Rogowski technique by using distributed reactance multiturn magnetic loops so that it is suitable for measuring current position as well as amplitude. Four identical stripline coils are wound one per quadrant around a non magnetic core. The sensitivity is similar to that of a lumped coil system, with the added advantage of increased bandwidth. The voltages induced on the four separate coils are compared and suitable signal conditioning is performed to recover beam position and intensity information.

  18. Beam position and total current monitor for heavy ion fusion beams

    SciTech Connect

    Berners, D.; Reginato, L.L.

    1992-10-01

    Heavy Ion Fusion requires moderate currents, 1-10A, for a duration of about 1 [mu]s. For accurate beam transport, the center of charge must be located to within [plus minus] 100 [mu]m. Beam position and intensity may be excited at frequencies approaching 10 MHz, and the monitoring system must have adequate bandwidth to respond at these frequencies. We have modified the Rogowski technique by using distributed reactance multiturn magnetic loops so that it is suitable for measuring current position as well as amplitude. Four identical stripline coils are wound one per quadrant around a non magnetic core. The sensitivity is similar to that of a lumped coil system, with the added advantage of increased bandwidth. The voltages induced on the four separate coils are compared and suitable signal conditioning is performed to recover beam position and intensity information.

  19. Theory of dynamic transformation of light beams by conduction electrons in semiconductors

    SciTech Connect

    Chumak, A.A.; Levshin, A.E.; Tomchuk, P.M.; Vinetskii, V.L.

    1986-08-01

    An expression describing the effect of nonstationary energy transfer in a photoresponsive medium is derived. The dynamic transformation of light beams by free charge carriers in multivalley semiconductors is considered. Estimates are obtained for the amplification factor GAMMA.

  20. Neutral Beam Current Drive in Spheromak plasma and plasma stability

    NASA Astrophysics Data System (ADS)

    Pearlstein, L. D.; Jayakumar, R. J.; Hudson, B.; Hill, D. N.; Lodestro, L. L.; McLean, H. S.; Fowler, T. K.; Casper, T. A.

    2007-11-01

    A key question for the Sustained Spheromak Physics Experiment (SSPX) is understanding how spheromaks can be sustained by other current drive tools such as neutral beam current drive. Another question is whether the present relationship between current and maximum spheromak magnetic field (plasma beta) is related to Alcator-like ohmic confinement limit or is a stability limit. Using the code CORSICA, the fraction of neutral beam current drive that can be achieved has been calculated for different injection angles with a fixed equilibrium. It is seen that relaxing the equilibrium with this drive simply drives the core safety factor to low values. Other equilibria where the NBI may give aligned current drive are being explored. Free-boundary equilibria calculations are underway to see what hyper-resistivity model gives the observed sustained SSPX performance and include that in the NBI calculations. Work performed under the auspices of the US DOE by University of California Lawrence Livermore National Laboratory under contract W-7405-ENG-48.

  1. High Accuracy Beam Current Monitor System for CEBAF'S Experimental Hall A

    SciTech Connect

    J. Denard; A. Saha; G. Lavessiere

    2001-07-01

    CEBAF accelerator delivers continuous wave (CW) electron beams to three experimental Halls. In Hall A, all experiments require continuous, non-invasive current measurements and a few experiments require an absolute accuracy of 0.2 % in the current range from 1 to 180 {micro}A. A Parametric Current Transformer (PCT), manufactured by Bergoz, has an accurate and stable sensitivity of 4 {micro}A/V but its offset drifts at the muA level over time preclude its direct use for continuous measurements. Two cavity monitors are calibrated against the PCT with at least 50 {micro}A of beam current. The calibration procedure suppresses the error due to PCT's offset drifts by turning the beam on and off, which is invasive to the experiment. One of the goals of the system is to minimize the calibration time without compromising the measurement's accuracy. The linearity of the cavity monitors is a critical parameter for transferring the accurate calibration done at high currents over the whole dynamic range. The method for measuring accurately the linearity is described.

  2. Experimental study on superconducting fault current limiting transformer for fault current suppression and system stability improvement

    NASA Astrophysics Data System (ADS)

    Kagawa, H.; Hayakawa, N.; Kashima, N.; Nagaya, S.; Okubo, H.

    2002-08-01

    We have been developing a superconducting fault current limiting transformer (SFCLT) with 3-phase, 500/275 kV, 625 MVA and optimized the main parameters by EMTP simulation. In this paper, we designed and fabricated an experimental scale-down model of SFCLT with 3-phase, 275/105 V, 6.25 kVA, using NbTi superconducting wire. We introduced the experimental model SFCLT into a transient network analyzer consisted of synchronous generators, transformers, transmission lines, circuit breakers and an infinite bus. It was revealed that experimental model had effective function-parameters as was simulated and experimental results clarified the effectiveness of SFCLT having both functions of the fault current suppression and the system stability improvement in a future superconducting power system.

  3. Hybrid monitor for both beam position and tilt of pulsed high-current beams

    SciTech Connect

    Pang, J. He, X.; Ma, C.; Zhao, L.; Li, Q.; Dai, Z.

    2014-09-15

    A Hybrid beam monitor, integrated with both azimuthal and axial B-dot probes, was designed for simultaneous measurement of both beam position and beam angle for pulsed high-current beams at the same location in beam pipe. The output signals of axial B-dot probes were found to be mixed with signals caused by transverse position deviation. In order to eliminate the unwanted signals, an elimination method was developed and its feasibility tested on a 50-Ω coaxial line test stand. By this method, a waveform, shape-like to that of input current and proportional to the tilt angle, was simulated and processed by following integration step to achieve the tilt angle. The tests showed that the measurement error of displacement and tilt angle less than 0.3 mm and 1.5 mrad, respectively. The latter error could be reduced with improved probes by reducing the inductance of the axial B-dot probe, but the improvement reached a limit due to some unknown systemic mechanism.

  4. A high-current calibration system based on indirect comparison of current transformer and Rogowski coil

    NASA Astrophysics Data System (ADS)

    Luo, Pandian; Li, Zhenhua; Li, Hongbin; Li, Hongfeng

    2013-12-01

    The calibration of the protective current transformer (CT) is of particular importance, since its accuracy at high currents is crucial to the correct operation of the subsequent relay protection devices. Conventional calibration methods have been using an electromagnetic CT which contains an iron core as the standard CT. The iron core is big and difficult to manufacture for high-current measurement, and the serious residual magnetism of the iron core at high currents can lead to excessive measurement errors. This paper proposes a calibration system based on indirect comparison of CT and Rogowski coil, i.e. using an iron-core CT to correct the error of the Rogowski coil at low currents, which may be caused by the position of the current-carrying conductor and so on, and then using the calibrated Rogowski coil as the standard transformer at high currents for its good linearity and wide dynamic range, and there is no magnetic saturation. Since the output of the Rogowski coil needs to be integrated, an improved digital integrator based on direct current (dc) negative feedback is adopted, which can effectively eliminate the influences of temperature drift, time drift and dc offset caused by the analogue circuit. The measurement errors of each part of the calibration system have also been discussed, and the test results show that the accuracy of the system can reach up to the 0.05S Class and the uncertainties are 0.038% for ratio and 0.68‧ for phase in the range 500 A to 50 kA.

  5. Cone beam CT: a current overview of devices

    PubMed Central

    Nemtoi, A; Czink, C; Haba, D; Gahleitner, A

    2013-01-01

    The purpose of this study was to review and compare the properties of all the available cone beam CT (CBCT) devices offered on the market, while focusing especially on Europe. In this study, we included all the different commonly used CBCT devices currently available on the European market. Information about the properties of each device was obtained from the manufacturers’ official available data, which was later confirmed by their representatives in cases where it was necessary. The main features of a total of 47 CBCT devices that are currently marketed by 20 companies were presented, compared and discussed in this study. All these CBCT devices differ in specific properties according to the companies that produce them. The summarized technical data from a large number of CBCT devices currently on the market offer a wide range of imaging possibilities in the oral and maxillofacial region. PMID:23818529

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

    SciTech Connect

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

    2015-01-09

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

  7. Isotopic germanium targets for high beam current applications at GAMMASPHERE.

    SciTech Connect

    Greene, J. P.; Lauritsen, T.

    2000-11-29

    The creation of a specific heavy ion residue via heavy ion fusion can usually be achieved through a number of beam and target combinations. Sometimes it is necessary to choose combinations with rare beams and/or difficult targets in order to achieve the physics goals of an experiment. A case in point was a recent experiment to produce {sup 152}Dy at very high spins and low excitation energy with detection of the residue in a recoil mass analyzer. Both to create the nucleus cold and with a small recoil-cone so that the efficiency of the mass analyzer would be high, it was necessary to use the {sup 80}Se on {sup 76}Ge reaction rather than the standard {sup 48}Ca on {sup 108}Pd reaction. Because the recoil velocity of the {sup 152}Dy residues was very high using this symmetric reaction (5% v/c), it was furthermore necessary to use a stack of two thin targets to reduce the Doppler broadening. Germanium targets are fragile and do not withstand high beam currents, therefore the {sup 76}Ge target stacks were mounted on a rotating target wheel. A description of the {sup 76}Ge target stack preparation will be presented and the target performance described.

  8. High-power Čerenkov microwave oscillators utilizing High-Current nanosecond Electron beams

    NASA Astrophysics Data System (ADS)

    Korovin, S. D.; Polevin, S. D.; Rostov, V. V.

    1996-12-01

    A short review is given of results obtained at the Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences on generating high-power microwave radiation. Most of the research was devoted to a study of stimulated Čerenkov radiation from relativistic electron beams. It is shown that the efficiency of a relativistic 3-cm backward wave tube with a nonuniform coupling resistance can reach 35%. High-frequency radiation was discovered in the emission spectrum of the Čerenkov oscillators and it was shown that the nature of the radiation was associated with the stimulated scattering of low-frequency radiation by the relativistic electrons. Radiation with a power of 500 MW was obtained in the 8-mm wavelength range using a two-beam Čerenkov oscillator. High-current pulse-periodic nanosecond accelerators with a charging device utilizing a Tesla transformer were used in the experiments. The possibility was demonstrated of generating high-power microwave radiation with a pulse-repetition frequency of up to 100 Hz. An average power of ˜500 W was achieved from the relativistic oscillators. A relativistic backward wave tube with a high-current electron beam was used to make a prototype nanosecond radar device. Some of the results presented were obtained jointly with the Russian Academy of Sciences Institute of Applied Physics. Questions concerning multiwave Čerenkov interaction are not considered in this paper.

  9. Effects of MHD instabilities on neutral beam current drive

    SciTech Connect

    Podestà, M.; Gorelenkova, M.; Darrow, D. S.; Fredrickson, E. D.; Gerhardt, S. P.; White, R. B.

    2015-04-17

    One of the primary tools foreseen for heating, current drive (CD) and q-profile control in future fusion reactors such as ITER and a Fusion Nuclear Science Facility is the neutral beam injection (NBI). However, fast ions from NBI may also provide the drive for energetic particle-driven instabilities (e.g. Alfvénic modes (AEs)), which in turn redistribute fast ions in both space and energy, thus hampering the control capabilities and overall efficiency of NB-driven current. Based on experiments on the NSTX tokamak (M. Ono et al 2000 Nucl. Fusion 40 557), the effects of AEs and other low-frequency magneto-hydrodynamic instabilities on NB-CD efficiency are investigated. When looking at the new fast ion transport model, which accounts for particle transport in phase space as required for resonant AE perturbations, is utilized to obtain consistent simulations of NB-CD through the tokamak transport code TRANSP. It is found that instabilities do indeed reduce the NB-driven current density over most of the plasma radius by up to ~50%. Moreover, the details of the current profile evolution are sensitive to the specific model used to mimic the interaction between NB ions and instabilities. Finally, implications for fast ion transport modeling in integrated tokamak simulations are briefly discussed.

  10. Effects of MHD instabilities on neutral beam current drive

    DOE PAGESBeta

    Podestà, M.; Gorelenkova, M.; Darrow, D. S.; Fredrickson, E. D.; Gerhardt, S. P.; White, R. B.

    2015-04-17

    One of the primary tools foreseen for heating, current drive (CD) and q-profile control in future fusion reactors such as ITER and a Fusion Nuclear Science Facility is the neutral beam injection (NBI). However, fast ions from NBI may also provide the drive for energetic particle-driven instabilities (e.g. Alfvénic modes (AEs)), which in turn redistribute fast ions in both space and energy, thus hampering the control capabilities and overall efficiency of NB-driven current. Based on experiments on the NSTX tokamak (M. Ono et al 2000 Nucl. Fusion 40 557), the effects of AEs and other low-frequency magneto-hydrodynamic instabilities on NB-CDmore » efficiency are investigated. When looking at the new fast ion transport model, which accounts for particle transport in phase space as required for resonant AE perturbations, is utilized to obtain consistent simulations of NB-CD through the tokamak transport code TRANSP. It is found that instabilities do indeed reduce the NB-driven current density over most of the plasma radius by up to ~50%. Moreover, the details of the current profile evolution are sensitive to the specific model used to mimic the interaction between NB ions and instabilities. Finally, implications for fast ion transport modeling in integrated tokamak simulations are briefly discussed.« less

  11. High-energy tritium beams as current drivers in tokamak reactors

    SciTech Connect

    Mikkelsen, D.R.; Grisham, L.R.

    1983-04-01

    The effect on neutral-beam design and reactor performance of using high-energy (approx. 3-10 MeV) tritium neutral beams to drive steady-state tokamak reactors is considered. The lower current of such beams leads to several advantages over lower-energy neutral beams. The major disadvantage is the reduction of the reactor output caused by the lower current-drive efficiency of the high-energy beams.

  12. Transforming a spatially coherent light beam into a diffused beam of small diffusion angle using suitable surface scattering

    NASA Astrophysics Data System (ADS)

    Dashtdar, M.; Tavassoly, M. T.

    2013-11-01

    Imposing a phase random distribution in an interval larger than 2π on a spatially coherent light beam transforms the beam into a diffuse one. However, if the required random phase distribution is imposed by a rough transparent plate immersed in a transparent liquid or covered by another transparent material of refractive index close to that of the plate, the diffused light is confined in a small cone around the light incident angle. This renders to fabricate diffusers with high transmission efficiency that has applications in computer displays, bar code scanners, and image forming systems including conventional optical microscopes.

  13. Current interruption and particle beam generation by a plasma focus

    NASA Astrophysics Data System (ADS)

    Gerdin, G.; Venneri, F.

    1982-11-01

    Through collaboration with Dr. K. H. Schoenbach of Texas Tech University the plasma focus opening switch (PFOS) was revised to answer basic questions as to utility of the concept. To estimate the plasma temperature and classical resistivity a soft X-ray spectrometer and X-ray pinhole camera were developed. The temperature was estimated from a coronal model to range between 0.4 to 0.5 keV for either a nitrogen or neon impurity (1 to 2%) in deuterium at 3 torr. Strong pinches were observed in pure neon (0.6 torr) with an electron temperature in the same range. The corresponding classical resistance of the pinch is 9 m omega whereas 500 m omega is more consistent with output voltage pulse and current flow at interruption indicating anomalous resistivity is present. A one-dimensional two-fluid computer code has been developed to model anomalous resistivity in the pinch phase and preliminary results are consistent with the snowplow model. The final analysis of the plasma focus particle beam generation experiments was completed and a strong correlation was found for the beam-target model as the mechanism for neutron production in the Illinois plasma focus device.

  14. Experimental validation of ultra-thin metalenses for N-beam emissions based on transformation optics

    NASA Astrophysics Data System (ADS)

    Zhang, Kuang; Ding, Xumin; Wo, Deliang; Meng, Fanrong; Wu, Qun

    2016-02-01

    A general design of metalenses for N-beam emissions is proposed based on transformation optics. A linear mapping function is adopted to achieve the homogeneous characterization of the transforming medium, which is therefore easy to be achieved compared with previous designs limited by inhomogeneity based on transformation optics. To verify the theoretical design, a four-beam antenna constructed with ultrathin, homogenous, and uniaxial anisotropic metalens is designed, fabricated, and measured. It is shown that the realized gain of the four-beam antenna is increased by 6 dB compared with the single dipole source, while working frequency and relative bandwidth are kept unchanged. The measured far-field pattern verifies theoretical design procedure.

  15. Generalised Hermite-Gaussian beams and mode transformations

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Chen, Yujie; Zhang, Yanfeng; Chen, Hui; Yu, Siyuan

    2016-05-01

    Generalised Hermite-Gaussian modes (gHG modes), an extended notion of Hermite-Gaussian modes (HG modes), are formed by the summation of normal HG modes with a characteristic function α, which can be used to unite conventional HG modes and Laguerre-Gaussian modes (LG modes). An infinite number of normalised orthogonal modes can thus be obtained by modulation of the function α. The gHG mode notion provides a useful tool in analysis of the deformation and transformation phenomena occurring in propagation of HG and LG modes with astigmatic perturbation.

  16. Rapid measurement of charged particle beam profiles using a current flux grating

    SciTech Connect

    Paul, Samit; Chowdhury, Abhishek; Bhattacharjee, Sudeep

    2015-02-15

    The principle and physics issues of charged particle beam diagnostics using a current flux grating are presented. Unidirectional array of conducting channels with interstitial insulating layers of spacing d is placed in the beam path to capture flux of charge and electronically reproduce an exact beam current profile with density variation. The role of secondary electrons due to the impinging particle beam (both electron and ion) on the probe is addressed and a correction factor is introduced. A 2-dimensional profile of the electron beam is obtained by rotating the probe about the beam axis. Finally, a comparison of measured beam profile with a Gaussian is presented.

  17. Wigner distribution and fractional Fourier transform for two-dimensional symmetric optical beams.

    PubMed

    Alieva, T; Bastiaans, M J

    2000-12-01

    A useful relationship between the fractional Fourier transform power spectra of a two-dimensional symmetric optical beam, on the one hand, and its Wigner distribution, on the other, is established. This relationship allows a significant simplification of the standard procedure for the reconstruction of the Wigner distribution from the field intensity distributions in the fractional Fourier domains. The Wigner distribution of a symmetric optical beam is analyzed, both in the coherent and in the partially coherent case. PMID:11140492

  18. Equipment for Beam Current and Electron Energy Monitoring During Industry Irradiation.

    NASA Astrophysics Data System (ADS)

    Zavadtsev, A. A.

    1997-05-01

    The electron beam irradiation sterilization is placed first among all types of medical items sterilization. The quality of sterilization is determined by value of dose, which is in one's turn determined by beam current, electron energy and beam scanning system parameters. Therefore this parameters have to be controlled during the irradiation process. The equipment for beam current and electron energy monitoring allows to control beam current, electron energy spectrum and nominal deflection of electron beam when scanning during the irradiation process each scanning period or, for example, each tenth period by request.

  19. Collinear Acousto-Optical Transformation of Bessel Light Beams in Biaxial Gyrotropic Crystals

    NASA Astrophysics Data System (ADS)

    Belyi, V. N.; Kulak, G. V.; Krokh, G. V.; Shakin, O. V.

    2016-05-01

    The collinear acousto-optical transformation of Bessel light beams in biaxial gyrotropic crystals into two annular, internal conical refraction beams with orthogonal elliptical polarization is studied. It is found that the diffraction efficiency is maximal (~50-60%) for low ultrasound intensities and varies slightly with further increases in acoustic power. At high ultrasound intensities, the intensities of the transmitted and diffracted annular beams differ insignificantly. The possible use of this acousto-optical interaction for creating collinear tuneable narrow-band acousto-optical filters at low ultrasonic frequencies is demonstrated.

  20. Current understanding and issues on electron beam injection in space

    NASA Technical Reports Server (NTRS)

    Papadopoulos, K.; Szuszczewicz, E. P.

    1988-01-01

    The status of the physics understanding involved in electron beam injection in space is reviewed. The paper examines our understanding of beam plasma interactions and their associated wave and energized particle spectra of the processes involved in the beam plasma discharge, and of the vehicle charge neutralization. 'Strawman' models are presented for comparison with experimental observations.

  1. Particle-in-cell simulations of electron beam control using an inductive current divider

    NASA Astrophysics Data System (ADS)

    Swanekamp, S. B.; Angus, J. R.; Cooperstein, G.; Ottinger, P. F.; Richardson, A. S.; Schumer, J. W.; Weber, B. V.

    2015-11-01

    Kinetic, time-dependent, electromagnetic, particle-in-cell simulations of the inductive current divider are presented. The inductive current divider is a passive method for controlling the trajectory of an intense, hollow electron beam using a vacuum structure that inductively splits the beam's return current. The current divider concept was proposed and studied theoretically in a previous publication [Swanekamp et al., Phys. Plasmas 22, 023107 (2015)]. A central post carries a portion of the return current (I1), while the outer conductor carries the remainder (I2) with the injected beam current given by Ib = I1 + I2. The simulations are in agreement with the theory which predicts that the total force on the beam trajectory is proportional to (I2-I1) and the force on the beam envelope is proportional to Ib. Independent control over both the current density and the beam angle at the target is possible by choosing the appropriate current-divider geometry. The root-mean-square (RMS) beam emittance (ɛRMS) varies as the beam propagates through the current divider to the target. For applications where control of the beam trajectory is desired and the current density at the target is similar to the current density at the entrance foil, there is a modest 20% increase in ɛRMS at the target. For other applications where the beam is pinched to a current density ˜5 times larger at the target, ɛRMS is 2-3 times larger at the target.

  2. Direct-current proton-beam measurements at Los Alamos

    SciTech Connect

    Sherman, Joseph; Stevens, Ralph R.; Schneider, J. David; Zaugg, Thomas

    1995-09-15

    Recently, a CW proton accelerator complex was moved from Chalk River Laboratories (CRL) to Los Alamos National Laboratory. This includes a 50-keV dc proton injector with a single-solenoid low-energy beam transport system (LEBT) and a CW 1.25-MeV, 267-MHz radiofrequency quadrupole (RFQ). The move was completed after CRL had achieved 55-mA CW operation at 1.25 MeV using 250-kW klystrode tubes to power the RFQ. These accelerator components are prototypes for the front end of a CW linac required for an accelerator-driven transmutation linac, and they provide early confirmation of some CW accelerator components. The injector (ion source and LEBT) and emittance measuring unit are installed and operational at Los Alamos. The dc microwave ion source has been operated routinely at 50-keV, 75-mA hydrogen-ion current. This ion source has demonstrated very good discharge and H2 gas efficiencies, and sufficient reliability to complete CW RFQ measurements at CRL. Proton fraction of 75% has been measured with 550-W discharge power. This high proton fraction removes the need for an analyzing magnet. Proton LEBT emittance measurements completed at Los Alamos suggest that improved transmission through the RFQ may be achieved by increasing the solenoid focusing current. Status of the final CW RFQ operation at CRL and the installation of the RFQ at Los Alamos will be given.

  3. Direct-current proton-beam measurements at Los Alamos

    SciTech Connect

    Sherman, J.; Stevens, R.R.; Schneider, J.D.; Zaugg, T.

    1994-08-01

    Recently, a CW proton accelerator complex was moved from Chalk River Laboratories (CRL) to Los Alamos National Laboratory. This includes a 50-keV dc proton injector with a single-solenoid low-energy beam transport system (LEBT) and a CW 1.25-MeV, 267-MHz radiofrequency quadrupole (RFQ). The move was completed after CRL had achieved 55-mA CW operation at 1.25 MeV using 250-kW klystrode tubes to power the RFQ. These accelerator components are prototypes for the front end of a CW linac required for an accelerator-driven transmutation linac, and they provide early confirmation of some CW accelerator components. The injector (ion source and LEBT) and emittance measuring unit are installed and operational at Los Alamos. The dc microwave ion source has been operated routinely at 50-keV, 75-mA hydrogen-ion current. This ion source has demonstrated very good discharge and H{sub 2} gas efficiencies, and sufficient reliability to complete CW RFQ measurements at CRL. Proton fraction of 75% has been measured with 550-W discharge power. This high proton fraction removes the need for an analyzing magnet. Proton LEBT emittance measurements completed at Los Alamos suggest that improved transmission through the RFQ may be achieved by increasing the solenoid focusing current. Status of the final CW RFQ operation at CRL and the installation of the RFQ at Los Alamos is given.

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

    SciTech Connect

    Ahle, Larry; Grote, Dave; Kwan, Joe

    2002-05-24

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

  5. Transformation of the optical vortex light beams in holographic elements with embedded phase singularities

    NASA Astrophysics Data System (ADS)

    Sviridova, S. V.; Bekshaev, A. Y.

    2012-01-01

    Transformations of spatial characteristics of optical vortex (OV) light beams at passing through a computer-generated hologram (CGH) that imparts an additional phase singularity ("fork" hologram) are investigated. The spatial structure of the diffracted beam is studied for different combinations of the incident OV order m, embedded topological charge of the CGH q and the diffraction order n. Variations of the intensity distribution are investigated experimentally. Due to the incident beam displacement with respect to the CGH optical axis, the diffracted beam profile is deformed, rotates in the azimuthal direction in agreement with the internal energy circulation and its 'center of gravity' is displaced orthogonally to the incident beam displacement. The results are compared with theoretical predictions based on two models of the incident OV beam. As, in experiment, the incident beam was created from the Gaussian beam passed another fork hologram, the Kummer beam model seems presumably more relevant but the standard Laguerre-Gaussian model in some cases fits the experimental data quite well.

  6. Transformation of the optical vortex light beams in holographic elements with embedded phase singularities

    NASA Astrophysics Data System (ADS)

    Sviridova, S. V.; Bekshaev, A. Y.

    2011-09-01

    Transformations of spatial characteristics of optical vortex (OV) light beams at passing through a computer-generated hologram (CGH) that imparts an additional phase singularity ("fork" hologram) are investigated. The spatial structure of the diffracted beam is studied for different combinations of the incident OV order m, embedded topological charge of the CGH q and the diffraction order n. Variations of the intensity distribution are investigated experimentally. Due to the incident beam displacement with respect to the CGH optical axis, the diffracted beam profile is deformed, rotates in the azimuthal direction in agreement with the internal energy circulation and its 'center of gravity' is displaced orthogonally to the incident beam displacement. The results are compared with theoretical predictions based on two models of the incident OV beam. As, in experiment, the incident beam was created from the Gaussian beam passed another fork hologram, the Kummer beam model seems presumably more relevant but the standard Laguerre-Gaussian model in some cases fits the experimental data quite well.

  7. Eigenfunctions and eigenoperators of cyclic integral transforms with application to Gaussian beam propagation

    NASA Astrophysics Data System (ADS)

    McCallum, Matthew S.

    An integral transform which reproduces a transformable input function after a finite number N of successive applications is known as a cyclic transform. Of course, such a transform will reproduce an arbitrary transformable input after N applications, but it also admits eigenfunction inputs which will be reproduced after a single application of the transform. These transforms and their eigenfunctions appear in various applications, and the systematic determination of eigenfunctions of cyclic integral transforms has been a problem of interest to mathematicians since at least the early twentieth century. In this work we review the various approaches to this problem, providing generalizations of published expressions from previous approaches. We then develop a new formalism, differential eigenoperators, that reduces the eigenfunction problem for a cyclic transform to an eigenfunction problem for a corresponding ordinary differential equation. In this way we are able to relate eigenfunctions of integral equations to boundary-value problems, which are typically easier to analyze. We give extensive examples and discussion via the specific case of the Fourier transform. We also relate this approach to two formalisms that have been of interest to the mathematical physics community---hyperdifferential operators and linear canonical transforms. We show how this new approach reproduces known results of Fourier optics regarding free-space diffractive propagation of Gaussian beams in both one and two dimensions. Finally we discuss the group-theoretical aspects of the formalism and describe an isomorphism between roots of the identity transform and complex roots of unity. In the appendix we derive several technical results related to integrability and transformability of solutions in the Fourier transform case, and we prove two theorems---one of them new---on polynomial roots. We conclude that the formalism offers a new and equally valuable perspective on an interesting

  8. Asymptotic normality of kernel estimators for images observed under the radon transform in fan beam design

    NASA Astrophysics Data System (ADS)

    Proksch, Katharina

    2013-10-01

    We consider a nonparametric, two-dimensional regression model that describes observations of Radon transformed images, i.e., an inverse regression model. Reconstructions from deterministic fan beam design by a certain kind of kernel-type estimators are considered and their asymptotic properties are investigated. The problem discussed is related to medical imaging procedures such as computerized tomography (CT).

  9. Improved Envelope And Centroid Equations for High Current Beams

    NASA Astrophysics Data System (ADS)

    Genoni, Thomas C.; Hughes, Thomas P.

    2002-04-01

    The standard envelope equation for electron beams (e.g., Lee-Cooper), neglects self-field contributions from the beam rotation and the slope of the beam envelope. We have carried out an expansion which includes these effects to first order, resulting in a new equation for the beam edge radius. The change in beam kinetic energy due to spacecharge depression as the beam radius varies is also included. For the centroid equation, we have included the "self-steering" effect due to the curvature of the beam orbit. To leading order, there is a cancellation between the self-steering effect and the spacecharge depression of the beam energy, so that a more accurate centroid equation is obtained by using the undepressed value of the energy (i.e., the total beam energy) to calculate the orbit. We have implemented the envelope and centroid equations in the LAMDA code. The effect of the new terms will be illustrated with calculations for the DARHT accelerators at Los Alamos National Laboratory.

  10. TRANSFORMER

    DOEpatents

    Baker, W.R.

    1959-08-25

    Transformers of a type adapted for use with extreme high power vacuum tubes where current requirements may be of the order of 2,000 to 200,000 amperes are described. The transformer casing has the form of a re-entrant section being extended through an opening in one end of the cylinder to form a coaxial terminal arrangement. A toroidal multi-turn primary winding is disposed within the casing in coaxial relationship therein. In a second embodiment, means are provided for forming the casing as a multi-turn secondary. The transformer is characterized by minimized resistance heating, minimized external magnetic flux, and an economical construction.

  11. Temperature calculations of heat loads in rotating target wheels exposed to high beam currents.

    SciTech Connect

    Greene, J. P.; Gabor, R.; Neubauer, J.

    2000-11-29

    In heavy-ion physics, high beam currents can eventually melt or destroy the target. Tightly focused beams on stationary targets of modest melting point will exhibit short lifetimes. Defocused or wobbled beams are employed to enhance target survival. Rotating targets using large diameter wheels can help overcome target melting and allow for higher beam currents to be used in experiments. The purpose of the calculations in this work is to try and predict the safe maximum beam currents which produce heat loads below the melting point of the target material.

  12. Improved Envelope and Centroid Equations for High Current Beams

    NASA Astrophysics Data System (ADS)

    Genoni, Thomas C.; Hughes, Thomas P.; Thoma, Carsten H.

    2002-12-01

    The standard envelope equation for charged particle beams (e.g., Lee-Cooper) neglects self-field contributions from the beam rotation and the slope of the beam envelope. We have carried out an expansion that includes these effects to first order, resulting in a new equation for the edge radius. The change in beam kinetic energy due to space-charge depression as the beam radius varies is also included. For the centroid equation, we have included the "self-steering" effect due to the curvature of the beam orbit. To leading order, there is a cancellation between the self-steering effect and the space-charge depression of the beam energy, so that a more accurate centroid equation is obtained by using the undepressed value of the energy (i.e., the total beam energy) to calculate the orbit. We have implemented the envelope and centroid equations in the Lamda code [1]. The effect of the new terms will be illustrated with calculations for the DARHT accelerators at the Los Alamos National Laboratory [2].

  13. Resistive wall heating due to image current on the beam chamber for a superconducting undulator.

    SciTech Connect

    Kim, S. H. )

    2012-03-27

    The image-current heating on the resistive beam chamber of a superconducting undulator (SCU) was calculated based on the normal and anomalous skin effects. Using the bulk resistivity of copper for the beam chamber, the heat loads were calculated for the residual resistivity ratios (RRRs) of unity at room temperature to 100 K at a cryogenic temperature as the reference. Then, using the resistivity of the specific aluminum alloy 6053-T5, which will be used for the SCU beam chamber, the heat loads were calculated. An electron beam stored in a storage ring induces an image current on the inner conducting wall, mainly within a skin depth, of the beam chamber. The image current, with opposite charge to the electron beam, travels along the chamber wall in the same direction as the electron beam. The average current in the storage ring consists of a number of bunches. When the pattern of the bunched beam is repeated according to the rf frequency, the beam current may be expressed in terms of a Fourier series. The time structure of the image current is assumed to be the same as that of the beam current. For a given resistivity of the chamber inner wall, the application ofthe normal or anomalous skin effect will depend on the harmonic numbers of the Fourier series of the beam current and the temperature of the chamber. For a round beam chamber with a ratius r, much larger than the beam size, one can assume that the image current density as well as the density square, may be uniform around the perimeter 2{pi}r. For the SCU beam chamber, which has a relatively narrow vertical gap compared to the width, the effective perimeter was estimated since the heat load should be proportional to the inverse of the perimeter.

  14. Controlling hollow relativistic electron beam orbits with an inductive current divider

    SciTech Connect

    Swanekamp, S. B.; Richardson, A. S.; Angus, J. R.; Cooperstein, G.; Hinshelwood, D. D.; Ottinger, P. F.; Rittersdorf, I. M.; Schumer, J. W.; Weber, B. V.; Zier, J. C.

    2015-02-06

    A passive method for controlling the trajectory of an intense, hollow electron beam is proposed using a vacuum structure that inductively splits the beam's return current. A central post carries a portion of the return current (I1), while the outer conductor carries the remainder (I2). An envelope equation appropriate for a hollow electron beam is derived and applied to the current divider. The force on the beam trajectory is shown to be proportional to (I2-I1), while the average force on the envelope (the beam width) is proportional to the beam current Ib = (I2 + I1). The values of I1 and I2 depend on the inductances in the return-current path geometries. Proper choice of the return-current geometries determines these inductances and offers control over the beam trajectory. As a result, solutions using realistic beam parameters show that, for appropriate choices of the return-current-path geometry, the inductive current divider can produce a beam that is both pinched and straightened so that it approaches a target at near-normal incidence with a beam diameter that is on the order of a few mm.

  15. Controlling hollow relativistic electron beam orbits with an inductive current divider

    DOE PAGESBeta

    Swanekamp, S. B.; Richardson, A. S.; Angus, J. R.; Cooperstein, G.; Hinshelwood, D. D.; Ottinger, P. F.; Rittersdorf, I. M.; Schumer, J. W.; Weber, B. V.; Zier, J. C.

    2015-02-06

    A passive method for controlling the trajectory of an intense, hollow electron beam is proposed using a vacuum structure that inductively splits the beam's return current. A central post carries a portion of the return current (I1), while the outer conductor carries the remainder (I2). An envelope equation appropriate for a hollow electron beam is derived and applied to the current divider. The force on the beam trajectory is shown to be proportional to (I2-I1), while the average force on the envelope (the beam width) is proportional to the beam current Ib = (I2 + I1). The values of I1more » and I2 depend on the inductances in the return-current path geometries. Proper choice of the return-current geometries determines these inductances and offers control over the beam trajectory. As a result, solutions using realistic beam parameters show that, for appropriate choices of the return-current-path geometry, the inductive current divider can produce a beam that is both pinched and straightened so that it approaches a target at near-normal incidence with a beam diameter that is on the order of a few mm.« less

  16. Controlling hollow relativistic electron beam orbits with an inductive current divider

    SciTech Connect

    Swanekamp, S. B.; Richardson, A. S.; Angus, J. R.; Cooperstein, G.; Hinshelwood, D. D.; Ottinger, P. F.; Rittersdorf, I. M.; Schumer, J. W.; Weber, B. V.; Zier, J. C.

    2015-02-15

    A passive method for controlling the trajectory of an intense, hollow electron beam is proposed using a vacuum structure that inductively splits the beam's return current. A central post carries a portion of the return current (I{sub 1}), while the outer conductor carries the remainder (I{sub 2}). An envelope equation appropriate for a hollow electron beam is derived and applied to the current divider. The force on the beam trajectory is shown to be proportional to (I{sub 2}-I{sub 1}), while the average force on the envelope (the beam width) is proportional to the beam current I{sub b} = (I{sub 2} + I{sub 1}). The values of I{sub 1} and I{sub 2} depend on the inductances in the return-current path geometries. Proper choice of the return-current geometries determines these inductances and offers control over the beam trajectory. Solutions using realistic beam parameters show that, for appropriate choices of the return-current-path geometry, the inductive current divider can produce a beam that is both pinched and straightened so that it approaches a target at near-normal incidence with a beam diameter that is on the order of a few mm.

  17. Heavy ion linac as a high current proton beam injector

    NASA Astrophysics Data System (ADS)

    Barth, Winfried; Adonin, Aleksey; Appel, Sabrina; Gerhard, Peter; Heilmann, Manuel; Heymach, Frank; Hollinger, Ralph; Vinzenz, Wolfgang; Vormann, Hartmut; Yaramyshev, Stepan

    2015-05-01

    A significant part of the experimental program at Facility for Antiproton and Ion Research (FAIR) is dedicated to pbar physics requiring a high number of cooled pbars per hour. The primary proton beam has to be provided by a 70 MeV proton linac followed by two synchrotrons. The new FAIR proton linac will deliver a pulsed proton beam of up to 35 mA of 36 μ s duration at a repetition rate of 4 Hz (maximum). The GSI heavy ion linac (UNILAC) is able to deliver world record uranium beam intensities for injection into the synchrotrons, but it is not suitable for FAIR relevant proton beam operation. In an advanced machine investigation program it could be shown that the UNILAC is able to provide for sufficient high intensities of CH3 beam, cracked (and stripped) in a supersonic nitrogen gas jet into protons and carbon ions. This advanced operational approach will result in up to 3 mA of proton intensity at a maximum beam energy of 20 MeV, 1 0 0 μ s pulse duration and a repetition rate of up to 2.7 Hz delivered to the synchrotron SIS18. Recent linac beam measurements will be presented, showing that the UNILAC is able to serve as a proton FAIR injector for the first time, while the performance is limited to 25% of the FAIR requirements.

  18. Performance analyses for fast variable optical attenuator-based optical current transformer

    NASA Astrophysics Data System (ADS)

    Wei, Pu; Chen, Chen; Wang, Xuefeng; Shan, Xuekang; Sun, Xiaohan

    2014-06-01

    In this paper, we analyze the performance of the electro-optic hybrid optical current transformer (HOCT) proposed by ourselves for high-voltage metering and protective relaying application. The transformer makes use of a fast variable optical attenuator (FVOA) to modulate the lightwave according to the voltage from the primary current sensor, such as low-power current transformer (LPCT). In order to improve the performance of the transformer, we use an optic-electro feedback loop with the PID control algorithm to compensate the nonlinearity of the FVOA. The linearity and accuracy of the transformer were analyzed and tested. The results indicate that the nonlinearity of the FVOA is completely compensated by the loop and the ratio and phase errors are under 0.07% and 5 minutes respectively, under the working power of less than 1 mW power. The transformer can be immune to the polarization and wavelength drift, and also robust against the environmental interference.

  19. Experimental validation of a transformation optics based lens for beam steering

    NASA Astrophysics Data System (ADS)

    Yi, Jianjia; Burokur, Shah Nawaz; de Lustrac, André

    2015-10-01

    A transformation optics based lens for beam control is experimentally realized and measured at microwave frequencies. Laplace's equation is adopted to construct the mapping between the virtual and physical spaces. The metamaterial-based lens prototype is designed using electric LC resonators. A planar microstrip antenna source is used as transverse electric polarized wave launcher for the lens. Both the far field radiation patterns and the near-field distributions have been measured to experimentally demonstrate the beam steering properties. Measurements agree quantitatively and qualitatively with numerical simulations, and a non-narrow frequency bandwidth operation is observed.

  20. Experimental validation of a transformation optics based lens for beam steering

    SciTech Connect

    Yi, Jianjia; Burokur, Shah Nawaz Lustrac, André de

    2015-10-12

    A transformation optics based lens for beam control is experimentally realized and measured at microwave frequencies. Laplace's equation is adopted to construct the mapping between the virtual and physical spaces. The metamaterial-based lens prototype is designed using electric LC resonators. A planar microstrip antenna source is used as transverse electric polarized wave launcher for the lens. Both the far field radiation patterns and the near-field distributions have been measured to experimentally demonstrate the beam steering properties. Measurements agree quantitatively and qualitatively with numerical simulations, and a non-narrow frequency bandwidth operation is observed.

  1. Particle-in-cell simulations of electron beam control using an inductive current divider

    DOE PAGESBeta

    Swanekamp, S. B.; Angus, J. R.; Cooperstein, G.; Ottinger, P. F.; Richardson, A. S.; Schumer, J. W.; Weber, B. V.

    2015-11-18

    Kinetic, time-dependent, electromagnetic, particle-in-cell simulations of the inductive current divider are presented. The inductive current divider is a passive method for controlling the trajectory of an intense, hollow electron beam using a vacuum structure that inductively splits the beam’s return current. The current divider concept was proposed and studied theoretically in a previous publication [Phys. Plasmas 22, 023107 (2015)] A central post carries a portion of the return current (I1) while the outer conductor carries the remainder (I2) with the injected beam current given by Ib=I1+I2. The simulations are in agreement with the theory which predicts that the total forcemore » on the beam trajectory is proportional to (I2-I1) and the force on the beam envelope is proportional to Ib. For a fixed central post, the beam trajectory is controlled by varying the outer conductor radius which changes the inductance in the return-current path. The simulations show that the beam emittance is approximately constant as the beam propagates through the current divider to the target. As a result, independent control over both the current density and the beam angle at the target is possible by choosing the appropriate return-current geometry.« less

  2. Particle-in-cell simulations of electron beam control using an inductive current divider

    SciTech Connect

    Swanekamp, S. B.; Angus, J. R.; Cooperstein, G.; Ottinger, P. F.; Richardson, A. S.; Schumer, J. W.; Weber, B. V.

    2015-11-18

    Kinetic, time-dependent, electromagnetic, particle-in-cell simulations of the inductive current divider are presented. The inductive current divider is a passive method for controlling the trajectory of an intense, hollow electron beam using a vacuum structure that inductively splits the beam’s return current. The current divider concept was proposed and studied theoretically in a previous publication [Phys. Plasmas 22, 023107 (2015)] A central post carries a portion of the return current (I1) while the outer conductor carries the remainder (I2) with the injected beam current given by Ib=I1+I2. The simulations are in agreement with the theory which predicts that the total force on the beam trajectory is proportional to (I2-I1) and the force on the beam envelope is proportional to Ib. For a fixed central post, the beam trajectory is controlled by varying the outer conductor radius which changes the inductance in the return-current path. The simulations show that the beam emittance is approximately constant as the beam propagates through the current divider to the target. As a result, independent control over both the current density and the beam angle at the target is possible by choosing the appropriate return-current geometry.

  3. RAMPING UP THE SNS BEAM CURRENT WITH THE LBNL BASELINE H- SOURCE

    SciTech Connect

    Stockli, Martin P; Han, Baoxi; Murray Jr, S N; Newland, Denny J; Pennisi, Terry R; Santana, Manuel; Welton, Robert F

    2009-01-01

    Over the last two years the Spallation Neutron Source (SNS) has ramped up the repetition rate, pulse length, and the beam current to reach 540 kW, which has challenged many subsystems including the H- source designed and built by Lawrence Berkeley National Laboratory (LBNL). This paper discusses the major modifications of the H- source implemented to consistently and routinely output the beam current required by the SNS beam power ramp up plan. At this time, 32 mA LINAC beam current are routinely produced, which meets the requirement for 690 kW planned for end of 2008. In June 2008, a 14-day production run used 37 mA, which is close to the 38 mA required for 1.44 MW. A medium energy beam transport (MEBT) beam current of 46 mA was demonstrated on September 2, 2008.

  4. Transformation and Transformational Leadership: A Review of the Current and Relevant Literature for Academic Radiologists.

    PubMed

    Thomson, Norman B; Rawson, James V; Slade, Catherine P; Bledsoe, Martin

    2016-05-01

    With the US healthcare system on an unsustainable course, change is inevitable. Changes in the healthcare landscape impacting radiology include changing payment models, rapid adoption of digital technology, changes in radiology resident certifying exams, and the rise of consumerism in health care. Academic Radiology will be part of that change with none of its missions spared. What matters is not that change is coming but how Academic Radiology responds to change. Do we ignore, adapt, adopt others' practices, or lead change? Change management or transformation is a management skill set that can be learned and developed. Transformational leadership is a leadership style defined by the relationships between the leaders and the followers and the results they are able to achieve together to meet organizational goals. In this paper, we provide a review of key change management theories, as well as practical advice for self-reflection and development of leadership behaviors that promote effective change management and organizational transformation, particularly in a complex industry like Academic Radiology. PMID:26971043

  5. Direct Measurement of Electron Beam Induced Currents in p-type Silicon

    SciTech Connect

    Han, M.G.; Zhu, Y.; Sasaki, K.; Kato, T.; Fisher, C.A.J.; Hirayama, T.

    2010-08-01

    A new method for measuring electron beam induced currents (EBICs) in p-type silicon using a transmission electron microscope (TEM) with a high-precision tungsten probe is presented. Current-voltage (I-V) curves obtained under various electron-beam illumination conditions are found to depend strongly on the current density of the incoming electron beam and the relative distance of the beam from the point of probe contact, consistent with a buildup of excess electrons around the contact. This setup provides a new experimental approach for studying minority carrier transport in semiconductors on the nanometer scale.

  6. Precise spectrum reconstruction of the Fourier transforms imaging spectrometer based on polarization beam splitters.

    PubMed

    Ren, Wenyi; Zhang, Chunmin; Jia, Chenling; Mu, Tingkui; Li, Qiwei; Zhang, Lin

    2013-04-15

    A method was proposed to precisely reconstruct the spectrum from the interferogram taken by the Fourier transform imaging spectrometer (FTIS) based on the polarization beam splitters. Taken the FTISs based on the Savart polariscope and Wollaston prism as examples, the distorted spectrums were corrected via the proposed method effectively. The feasibility of the method was verified via simulation. The distorted spectrum, recovered from the interferogram taken by the polarization imaging spectrometer developed by us, was corrected. PMID:23595463

  7. Drug policy in China. Transformations, current status and future prospects.

    PubMed

    Liu, X; Li, S

    1997-07-01

    The pharmaceutical sector in China developed rapidly with the implementation of the market-oriented economic reforms, which began at the end of the 1970s. From 1980 to 1988 the production of drugs quadrupled, subsequently increasing at an annual rate of 20%, and consumption of drugs correspondingly increased. The increase in drug production was largely a result of the increase in the number of pharmaceutical companies, particularly the number of private joint ventures, of which there were none in 1980 and 1900 in 1994, accounting for 37% of the total number of pharmaceutical companies. With the transformation of the Chinese pharmaceutical market, some new problems have appeared. The low efficiency of pharmaceutical companies, poor-quality drugs, unfair competition and misuse of drugs have been of great concern to the Chinese government. Some countermeasures have been taken, but the problems remain. Increases in the age of the Chinese population, increases in income and changes in disease patterns, together with membership of the World Trade Organization will promote the development of the pharmaceutical market. However, health-insurance reform, an essential drug list, the separation of drugs from services, and controls on the increases in hospital revenue will reduce the demand for drugs. Pharmaceutical companies in China face both opportunities and challenges. The trend in development of the pharmaceutical market depends on the outcome of the interaction between the factors that increase, and those that decrease, the demand for drugs. While the general trend is towards an increase in the demand for drugs and the expansion of the pharmaceutical market, downward fluctuation is inevitable if effective health reforms of cost control are introduced nationwide. PMID:10169383

  8. Particle-in-cell simulations of electron beam control using an inductive current divider

    SciTech Connect

    Swanekamp, S. B.; Angus, J. R.; Cooperstein, G.; Ottinger, P. F.; Richardson, A. S.; Schumer, J. W.; Weber, B. V.

    2015-11-15

    Kinetic, time-dependent, electromagnetic, particle-in-cell simulations of the inductive current divider are presented. The inductive current divider is a passive method for controlling the trajectory of an intense, hollow electron beam using a vacuum structure that inductively splits the beam's return current. The current divider concept was proposed and studied theoretically in a previous publication [Swanekamp et al., Phys. Plasmas 22, 023107 (2015)]. A central post carries a portion of the return current (I{sub 1}), while the outer conductor carries the remainder (I{sub 2}) with the injected beam current given by I{sub b} = I{sub 1} + I{sub 2}. The simulations are in agreement with the theory which predicts that the total force on the beam trajectory is proportional to (I{sub 2}−I{sub 1}) and the force on the beam envelope is proportional to I{sub b}. Independent control over both the current density and the beam angle at the target is possible by choosing the appropriate current-divider geometry. The root-mean-square (RMS) beam emittance (ε{sub RMS}) varies as the beam propagates through the current divider to the target. For applications where control of the beam trajectory is desired and the current density at the target is similar to the current density at the entrance foil, there is a modest 20% increase in ε{sub RMS} at the target. For other applications where the beam is pinched to a current density ∼5 times larger at the target, ε{sub RMS} is 2–3 times larger at the target.

  9. Elimination of the induced current error in magnetometers using superconducting flux transformers

    SciTech Connect

    Dummer, D.; Weyhmann, W.

    1987-10-01

    The changing magnetization of a sample in a superconducting flux transformer coupled magnetometer induces a current in the transformer which in turn changes the field at the sample. This ''image'' field and the error caused by it can be eliminated by sensing the current in the loop and nulling it by feedback through a mutual inductance. We have tested the technique on the superconducting transition of indium in an applied magnetic field and shown that the observed width of the transition is greatly reduced by maintaining zero current in the flux transformer.

  10. Microstructures and properties of zirconium-702 irradiated by high current pulsed electron beam

    NASA Astrophysics Data System (ADS)

    Yang, Shen; Cai, Jie; Lv, Peng; Zhang, Conglin; Huang, Wei; Guan, Qingfeng

    2015-09-01

    The microstructure, hardness and corrosion resistance of zirconium-702 before and after high-current pulsed electron beam (HCPEB) irradiation have been investigated. The microstructure evolution and surface morphologies of the samples were characterized by using X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The experimental results indicate that the sample surface was melted after HCPEB irradiation, and martensitic phase transformation occurred. Besides, two kinds of craters as well as ultrafine structures were obtained in the melted layer. TEM observations suggest that high density dislocations and deformation twins were formed after HCPEB irradiation. With the increasing of pulses, microhardness of the irradiated samples was increased from the initial 178 Hv to 254 Hv. The corrosion resistance was tested by using electrode impedance spectroscopy (EIS) and potentiodynamic polarization curves. Electrochemical results show that, after HCPEB irradiation, all the samples had better corrosion resistance in 1 mol HNO3 solution compared to the initial one, among which the 5-pulsed sample owned the best corrosion resistance. Ultrafine structures, martensitic phase transformation, surface porosities, dislocations and deformation twins are believed to be the dominant reasons for the improvement of the hardness and corrosion resistance.

  11. A NEW DIFFERENTIAL AND ERRANT BEAM CURRENT MONITOR FOR THE SNS* ACCELERATOR

    SciTech Connect

    Blokland, Willem; Peters, Charles C

    2013-01-01

    A new Differential and errant Beam Current Monitor (DBCM) is being implemented for both the Spallation Neutron Source's Medium Energy Beam Transport (MEBT) and the Super Conducting Linac (SCL) accelerator sections. These new current monitors will abort the beam when the difference between two toroidal pickups exceeds a threshold. The MEBT DBCM will protect the MEBT chopper target, while the SCL DBCM will abort beam to minimize fast beam losses in the SCL cavities. The new DBCM will also record instances of errant beam, such as beam dropouts, to assist in further optimization of the SNS Accelerator. A software Errant Beam Monitor was implemented on the regular BCM hardware to study errant beam pulses. The new system will take over this functionality and will also be able to abort beam on pulse-to-pulse variations. Because the system is based on the FlexRIO hardware and programmed in LabVIEW FPGA, it will be able to abort beam in about 5 us. This paper describes the development, implementation, and initial test results of the DBCM, as well as errant beam examples.

  12. Increasing Extracted Beam Current Density in Ion Thrusters through Plasma Potential Modification

    NASA Astrophysics Data System (ADS)

    Arthur, Neil; Foster, John

    2015-09-01

    A gridded ion thruster's maximum extractable beam current is determined by the space charge limit. The classical formulation does not take into account finite ion drift into the acceleration gap. It can be shown that extractable beam current can be increased beyond the conventional Child-Langmuir law if the ions enter the gap at a finite drift speed. In this work, ion drift in a 10 cm thruster is varied by adjusting the plasma potential relative to the potential at the extraction plane. Internal plasma potential variations are achieved using a novel approach involving biasing the magnetic cusps. Ion flow variations are assessed using simulated beam extraction in conjunction with a retarding potential analyzer. Ion beam current density changes at a given total beam voltage in full beam extraction tests are characterized as a function of induced ion drift velocity as well.

  13. Determination of Vapor Pressure-Temperature Relationships of Current Use Pesticides and Transformation Products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sub-cooled liquid vapor pressures of current use organochlorine and organophosphate pesticides (chlorothalonil, chlorpyrifos methyl, diazinon, fipronil) and selected transformation products (chlorpyrifos oxon, heptachlor epoxide, oxychlordane, 3,5,6-trichloro-2-pyridinol) were determined at multiple...

  14. Improved electron beam weld design and control with beam current profile measurements

    NASA Astrophysics Data System (ADS)

    Giedt, Warren H.

    The determination of machine settings for making an electron beam weld still involves trial and error tests. Also, even after settings are selected, serious variations in penetration may occur. Results are presented to demonstrate that improved weld consistency and quality can be obtained with measurement of the beam size and intensity distribution.

  15. Acceleration and stability of a high-current ion beam in induction fields

    NASA Astrophysics Data System (ADS)

    Karas', V. I.; Manuilenko, O. V.; Tarakanov, V. P.; Federovskaya, O. V.

    2013-03-01

    A one-dimensional nonlinear analytic theory of the filamentation instability of a high-current ion beam is formulated. The results of 2.5-dimensional numerical particle-in-cell simulations of acceleration and stability of an annular compensated ion beam (CIB) in a linear induction particle accelerator are presented. It is shown that additional transverse injection of electron beams in magnetically insulated gaps (cusps) improves the quality of the ion-beam distribution function and provides uniform beam acceleration along the accelerator. The CIB filamentation instability in both the presence and the absence of an external magnetic field is considered.

  16. Acceleration and stability of a high-current ion beam in induction fields

    SciTech Connect

    Karas', V. I.; Manuilenko, O. V.; Tarakanov, V. P.; Federovskaya, O. V.

    2013-03-15

    A one-dimensional nonlinear analytic theory of the filamentation instability of a high-current ion beam is formulated. The results of 2.5-dimensional numerical particle-in-cell simulations of acceleration and stability of an annular compensated ion beam (CIB) in a linear induction particle accelerator are presented. It is shown that additional transverse injection of electron beams in magnetically insulated gaps (cusps) improves the quality of the ion-beam distribution function and provides uniform beam acceleration along the accelerator. The CIB filamentation instability in both the presence and the absence of an external magnetic field is considered.

  17. A stationary wavelet transform based approach to registration of planning CT and setup cone beam-CT images in radiotherapy.

    PubMed

    Deng, Jun-Min; Yue, Hai-Zhen; Zhuo, Zhi-Zheng; Yan, Hua-Gang; Liu, Di; Li, Hai-Yun

    2014-05-01

    Image registration between planning CT images and cone beam-CT (CBCT) images is one of the key technologies of image guided radiotherapy (IGRT). Current image registration methods fall roughly into two categories: geometric features-based and image grayscale-based. Mutual information (MI) based registration, which belongs to the latter category, has been widely applied to multi-modal and mono-modal image registration. However, the standard mutual information method only focuses on the image intensity information and overlooks spatial information, leading to the instability of intensity interpolation. Due to its use of positional information, wavelet transform has been applied to image registration recently. In this study, we proposed an approach to setup CT and cone beam-CT (CBCT) image registration in radiotherapy based on the combination of mutual information (MI) and stationary wavelet transform (SWT). Firstly, SWT was applied to generate gradient images and low frequency components produced in various levels of image decomposition were eliminated. Then inverse SWT was performed on the remaining frequency components. Lastly, the rigid registration of gradient images and original images was implemented using a weighting function with the normalized mutual information (NMI) being the similarity measure, which compensates for the lack of spatial information in mutual information based image registration. Our experiment results showed that the proposed method was highly accurate and robust, and indicated a significant clinical potential in improving the accuracy of target localization in image guided radiotherapy (IGRT). PMID:24729043

  18. Beam and pump currents for a MARS anchor

    SciTech Connect

    Stroud, P.D.; Devoto, R.S.

    1982-01-01

    The MARS anchor has been modeled and analyzed with a numerical bounce-average Fokker-Planck treatment. The interactions between the various ion classes (passing, spanning and trapped) are treated in detail. Consistent solutions have been obtained for the complete asymmetric anchor. For baseline MARS parameters, 5.7 MW per end must be delivered by the anchor neutral beams, and 6.5 A per end must be pumped to maintain the sloshing ion axial density profiles.

  19. Nonlinear Charge and Current Neutralization of an Ion Beam Pulse in a Pre-formed Plasma

    SciTech Connect

    Igor D. Kaganovich; Gennady Shvets; Edward Startsev; Ronald C. Davidson

    2001-01-30

    The propagation of a high-current finite-length ion beam in a cold pre-formed plasma is investigated. The outcome of the calculation is the quantitative prediction of the degree of charge and current neutralization of the ion beam pulse by the background plasma. The electric magnetic fields generated by the ion beam are studied analytically for the nonlinear case where the plasma density is comparable in size with the beam density. Particle-in-cell simulations and fluid calculations of current and charge neutralization have been performed for parameters relevant to heavy ion fusion assuming long, dense beams with el >> V(subscript b)/omega(subscript b), where V(subscript b) is the beam velocity and omega subscript b is the electron plasma frequency evaluated with the ion beam density. An important conclusion is that for long, nonrelativistic ion beams, charge neutralization is, for all practical purposes, complete even for very tenuous background plasmas. As a result, the self-magnetic force dominates the electric force and the beam ions are always pinched during beam propagation in a background plasma.

  20. A new method of rapid power measurement for MW-scale high-current particle beams

    NASA Astrophysics Data System (ADS)

    Xu, Yongjian; Hu, Chundong; Xie, Yuanlai; Liu, Zhimin; Xie, Yahong; Liu, Sheng; Liang, Lizheng; Jiang, Caichao; Sheng, Peng; Yu, Ling

    2015-09-01

    MW-scale high current particle beams are widely applied for plasma heating in the magnetic confinement fusion devices, in which beam power is an important indicator for efficient heating. Generally, power measurement of MW-scale high current particle beam adopts water flow calorimetry (WFC). Limited by the principles of WFC, the beam power given by WFC is an averaged value. In this article a new method of beam power for MW-scale high-current particle beams is introduced: (1) the temperature data of thermocouples embedded in the beam stopping elements were obtained using high data acquire system, (2) the surface heat flux of the beam stopping elements are calculated using heat transfer, (3) the relationships between positions and heat flux were acquired using numerical simulation, (4) the real-time power deposited on the beam stopping elements can be calculated using surface integral. The principle of measurement was described in detail and applied to the EAST neutral beam injector for demonstration. The result is compared with that measured by WFC. Comparison of the results shows good accuracy and applicability of this measuring method.

  1. Transport and Measurements of High-Current Electron Beams from X pinches

    NASA Astrophysics Data System (ADS)

    Agafonov, Alexey V.; Mingaleev, Albert R.; Romanova, Vera M.; Tarakanov, Vladimir P.; Shelkovenko, Tatiana A.; Pikuz, Sergey A.; Blesener, Isaac C.; Kusse, Bruce R.; Hammer, David A.

    2009-01-01

    Generation of electron beams is an unavoidable property of X-pinches and other pulsed-power-driven pinches of different geometry. Some issues concerning high-current electron beam transport from the X pinch to the diagnostic system and measurements of the beam current by Faraday cups with different geometry's are discussed. Of particular interest is the partially neutralized nature of the beam propagating from the X-pinch to a diagnostic system. Two scenarios of electron beam propagation from X-pinch to Faraday cup are analyzed by means of computer simulation using the PIC-code KARAT. The first is longitudinal neutralization by ions extracted from plasma at an output window of the X-pinch diode; the second is the beam transport through a plasma background between the diode and a diagnostic system.

  2. Transport and Measurements of High-Current Electron Beams from X pinches

    SciTech Connect

    Agafonov, Alexey V.; Mingaleev, Albert R.; Romanova, Vera M.; Tarakanov, Vladimir P.; Shelkovenko, Tatiana A.; Pikuz, Sergey A.; Blesener, Isaac C.; Kusse, Bruce R.; Hammer, David A.

    2009-01-21

    Generation of electron beams is an unavoidable property of X-pinches and other pulsed-power-driven pinches of different geometry. Some issues concerning high-current electron beam transport from the X pinch to the diagnostic system and measurements of the beam current by Faraday cups with different geometry's are discussed. Of particular interest is the partially neutralized nature of the beam propagating from the X-pinch to a diagnostic system. Two scenarios of electron beam propagation from X-pinch to Faraday cup are analyzed by means of computer simulation using the PIC-code KARAT. The first is longitudinal neutralization by ions extracted from plasma at an output window of the X-pinch diode; the second is the beam transport through a plasma background between the diode and a diagnostic system.

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

    SciTech Connect

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

    2014-11-14

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

  4. A 128-channel picoammeter system and its application on charged particle beam current distribution measurements

    SciTech Connect

    Yu, Deyang Liu, Junliang; Xue, Yingli; Zhang, Mingwu; Cai, Xiaohong; Hu, Jianjun; Dong, Jinmei; Li, Xin

    2015-11-15

    A 128-channel picoammeter system is constructed based on instrumentation amplifiers. Taking advantage of a high electric potential and narrow bandwidth in DC energetic charged beam measurements, a current resolution better than 5 fA can be achieved. Two sets of 128-channel strip electrodes are implemented on printed circuit boards and are employed for ion and electron beam current distribution measurements. Tests with 60 keV O{sup 3+} ions and 2 keV electrons show that it can provide exact boundaries when a positive charged particle beam current distribution is measured.

  5. A 128-channel picoammeter system and its application on charged particle beam current distribution measurements

    NASA Astrophysics Data System (ADS)

    Yu, Deyang; Liu, Junliang; Xue, Yingli; Zhang, Mingwu; Cai, Xiaohong; Hu, Jianjun; Dong, Jinmei; Li, Xin

    2015-11-01

    A 128-channel picoammeter system is constructed based on instrumentation amplifiers. Taking advantage of a high electric potential and narrow bandwidth in DC energetic charged beam measurements, a current resolution better than 5 fA can be achieved. Two sets of 128-channel strip electrodes are implemented on printed circuit boards and are employed for ion and electron beam current distribution measurements. Tests with 60 keV O3+ ions and 2 keV electrons show that it can provide exact boundaries when a positive charged particle beam current distribution is measured.

  6. Effect of the electrostatic plasma lens on the emittance of ahigh-current heavy ion beam

    SciTech Connect

    Chekh, Yu.; Goncharov, A.; Protsenko, I.; Brown, I.G.

    2004-01-10

    We describe measurements we have made of the emittance of a high-current, moderate-energy ion beam after transport through a permanent-magnet electrostatic plasma lens. The results indicate the absence of emittance growth due to the lens, when the lens is adjusted for optimal beam focusing. The measured emittance for a 16 keV Cu{sup 2+} ion beam formed by a vacuum arc ion source was about 0.4 {pi} {center_dot} mm {center_dot} mrad at a beam current of 50 mA rising more-or-less linearly to 1.5 {pi} {center_dot} mm {center_dot} mrad at 250 mA, and was conserved in beam transport through the lens. These results have significance for the application of high-current ion sources and the electrostatic plasma lens to particle accelerator injection.

  7. Formation of an ion beam in an elementary cell with inhomogeneous emission current density

    SciTech Connect

    Kotelnikov, I. A.; Davydenko, V. I.; Ivanov, A. A.; Tiunov, M. A.

    2008-02-15

    A well-known Pierce solution that allows focusing a beam of charged particles using properly shaped electrodes outside the beam aperture is generalized to the case of an accelerating system with inhomogeneous emission current density. It is shown that the defocusing effect of the space charge can, in principle, be evenly compensated over the entire cross section of the beam. In contrast to the beam with a uniform emission current density, both the electric potential and the transverse electric field must be controlled along the beam boundary in order to eliminate the angular divergence. However, eliminating the angular spread evenly across the beam constitutes a mathematically ill-posed problem which needs to be solved with the use of one or another method of regularization. An alternative way of diminishing beam emittance is proposed for the beam where the emission current is uniform across the entire aperture except for a narrow beam edge layer and a simple formula for the Pierce electrodes is derived. Numerical simulation has proved the reasonable accuracy of our analytical theory.

  8. Formation of an ion beam in an elementary cell with inhomogeneous emission current density.

    PubMed

    Kotelnikov, I A; Davydenko, V I; Ivanov, A A; Tiunov, M A

    2008-02-01

    A well-known Pierce solution that allows focusing a beam of charged particles using properly shaped electrodes outside the beam aperture is generalized to the case of an accelerating system with inhomogeneous emission current density. It is shown that the defocusing effect of the space charge can, in principle, be evenly compensated over the entire cross section of the beam. In contrast to the beam with a uniform emission current density, both the electric potential and the transverse electric field must be controlled along the beam boundary in order to eliminate the angular divergence. However, eliminating the angular spread evenly across the beam constitutes a mathematically ill-posed problem which needs to be solved with the use of one or another method of regularization. An alternative way of diminishing beam emittance is proposed for the beam where the emission current is uniform across the entire aperture except for a narrow beam edge layer and a simple formula for the Pierce electrodes is derived. Numerical simulation has proved the reasonable accuracy of our analytical theory. PMID:18315193

  9. Transformer-rectifier flux pump using inductive current transfer and thermally controlled Nb(3)Sn cryotrons.

    PubMed

    Atherton, D L; Davies, R

    1979-10-01

    Transformer-rectifier flux pumps using thermally switched Nb(3)Sn cryotrons are being investigated as a loss make-up device for the proposed isochorically operated (sealed) superconducting magnets for the Canadian Maglev vehicle. High currents (1000 A) were obtained in an experimental flux pump using inductive current transfer and operating at 2 Hz. PMID:18699368

  10. Numerical Simulation of Non-Inductive Current Driven Scenario in EAST Using Neutral Beam Injection

    NASA Astrophysics Data System (ADS)

    Li, Hao; Wu, Bin; Wang, Jinfang; Wang, Ji; Hu, Chundong

    2015-01-01

    For achieving the scientific mission of long pulse and high performance operation, experimental advanced superconducting tokamak (EAST) applies fully superconducting magnet technology and is equiped with high power auxiliary heating system. Besides RF (Radio Frequency) wave heating, neutral beam injection (NBI) is an effective heating and current drive method in fusion research. NBCD (Neutral Beam Current Drive) as a viable non-inductive current drive source plays an important role in quasi-steady state operating scenario for tokamak. The non-inductive current driven scenario in EAST only by NBI is predicted using the TSC/NUBEAM code. At the condition of low plasma current and moderate plasma density, neutral beam injection heats the plasma effectively and NBCD plus bootstrap current accounts for a large proportion among the total plasma current for the flattop time.

  11. The backward phase flow and FBI-transform-based Eulerian Gaussian beams for the Schrödinger equation

    NASA Astrophysics Data System (ADS)

    Leung, Shingyu; Qian, Jianliang

    2010-11-01

    We propose the backward phase flow method to implement the Fourier-Bros-Iagolnitzer (FBI)-transform-based Eulerian Gaussian beam method for solving the Schrödinger equation in the semi-classical regime. The idea of Eulerian Gaussian beams has been first proposed in [12]. In this paper we aim at two crucial computational issues of the Eulerian Gaussian beam method: how to carry out long-time beam propagation and how to compute beam ingredients rapidly in phase space. By virtue of the FBI transform, we address the first issue by introducing the reinitialization strategy into the Eulerian Gaussian beam framework. Essentially we reinitialize beam propagation by applying the FBI transform to wavefields at intermediate time steps when the beams become too wide. To address the second issue, inspired by the original phase flow method, we propose the backward phase flow method which allows us to compute beam ingredients rapidly. Numerical examples demonstrate the efficiency and accuracy of the proposed algorithms.

  12. Comment on paper: "Generation of dark hollow beams by using a fractional radial Hilbert transform system"

    NASA Astrophysics Data System (ADS)

    Ez-zariy, L.; Nebdi, H.; Belafhal, A.

    2015-12-01

    This paper comments on a recently published work dealing with: "Generation of dark hollow beams by using a radial Hilbert transform system" by Q. Xie and D. Zhao, Opt. Commun. 275 (2007) 394. The authors have applied an integral, valid only for the integer orders, in cases of fractional ones. In addition, in their main result established by Eq. (11), the authors have neglected the dependence of some terms on the parameter summation. So, in the actual comment, we will give the main exact closed-form of the considered theory.

  13. Fully phase multiple information encoding based on superposition of two beams and Fresnel-transform domain

    NASA Astrophysics Data System (ADS)

    Abuturab, Muhammad Rafiq

    2015-12-01

    A novel asymmetric multiple information encoding using superposition of two beams and Fresnel transform, is proposed. In this scheme, each channel of individual user image is separately phase encoded and then modulated by random phase mask. The three modulated user channels are independently multiplied to produce three complex user channels. They are individually multiplied with three channels of carrier image and Fresnel transformed, and then phase- and amplitude truncated to produce first set of three encrypted channels and three asymmetric keys. Now each channel of secret image is normalized, phase-only masked, and then independently multiplied by corresponding modulated user channels. The three resultant channels are separately multiplied to construct three complex secret channels. Afterward, the three encrypted channels are multiplied with corresponding three complex secret channels and Fresnel transformed, and then phase- and amplitude truncated to obtain second set of three encrypted channels and three asymmetric keys. The wavelengths and propagation distances of two Fresnel transforms, and two asymmetric keys are common keys to all authorized-users, while two individual keys are provided to each authorized-user. The encryption process is implemented digitally while the decryption process can be performed optoelectronically. The proposed method is asymmetric, noniterative and larger multiplexing capacity without any cross-talk noise effects. Owing to the individual user image based method, high robustness against existing attacks can be achieved. Numerical simulation results demonstrate that the proposed method is feasible and efficient.

  14. Thermally induced transformations of amorphous carbon nanostructures fabricated by electron beam induced deposition.

    PubMed

    Kulkarni, Dhaval D; Rykaczewski, Konrad; Singamaneni, Srikanth; Kim, Songkil; Fedorov, Andrei G; Tsukruk, Vladimir V

    2011-03-01

    We studied the thermally induced phase transformations of electron-beam-induced deposited (EBID) amorphous carbon nanostructures by correlating the changes in its morphology with internal microstructure by using combined atomic force microscopy (AFM) and high resolution confocal Raman microscopy. These carbon deposits can be used to create heterogeneous junctions in electronic devices commonly known as carbon-metal interconnects. We compared two basic shapes of EBID deposits: dots/pillars with widths from 50 to 600 nm and heights from 50 to 500 nm and lines with variable heights from 10 to 150 nm but having a constant length of 6 μm. We observed that during thermal annealing, the nanoscale amorphous deposits go through multistage transformation including dehydration and stress-relaxation around 150 °C, dehydrogenation within 150-300 °C, followed by graphitization (>350 °C) and formation of nanocrystalline, highly densified graphitic deposits around 450 °C. The later stage of transformation occurs well below commonly observed graphitization for bulk carbon (600-800 °C). It was observed that the shape of the deposits contribute significantly to the phase transformations. We suggested that this difference is controlled by different contributions from interfacial footprints area. Moreover, the rate of graphitization was different for deposits of different shapes with the lines showing a much stronger dependence of its structure on the density than the dots. PMID:21319745

  15. Transforming nursing education: a review of current curricular practices in relation to Benner's latest work.

    PubMed

    Handwerker, Sarah M

    2012-01-01

    Current societal and healthcare system trends highlight the need to transform nursing education to prepare nurses capable of outstanding practice in the 21st century. Patricia Benner and colleagues urged nurse educators to transform their practice in the 2010 publication Educating Nurses, A Call to Radical Transformation. Frequently utilized pedagogical frameworks in nursing education include behaviorism and constructivism. Much of the structure and basis for instruction and evaluation can be found rooted in these philosophies. By first exploring both behaviorism and constructivism and then relating their use in nursing education to the call to transform, educators can be encourage to examine current practice and possibly modify aspects to include more rich experiential learning. PMID:23092804

  16. A DSP-Based Beam Current Monitoring System for Machine Protection Using Adaptive Filtering

    SciTech Connect

    J. Musson; H. Dong; R. Flood; C. Hovater; J. Hereford

    2001-06-01

    The CEBAF accelerator at Jefferson Lab is currently using an analog beam current monitoring (BCM) system for its machine protection system (MPS), which has a loss accuracy of 2 micro-amps. Recent burn-through simulations predict catastrophic beam line component failures below 1 micro-amp of loss, resulting in a blind spot for the MPS. Revised MPS requirements target an ultimate beam loss accuracy of 250 nA. A new beam current monitoring system has been developed which utilizes modern digital receiver technology and digital signal processing concepts. The receiver employs a direct-digital down converter integrated circuit, mated with a Jefferson Lab digital signal processor VME card. Adaptive filtering is used to take advantage of current-dependent burn-through rates. Benefits of such a system include elimination of DC offsets, generic algorithm development, extensive filter options, and interfaces to UNIX-based control systems.

  17. Sparking limits, cavity loading, and beam breakup instability associated with high-current rf linacs

    SciTech Connect

    Faehl, R.J.; Lemons, D.S.; Thode, L.E.

    1982-01-01

    The limitations on high-current rf linacs due to gap sparking, cavity loading, and the beam breakup instability are studied. It appears possible to achieve cavity accelerating gradients as high as 35 MV/m without sparking. Furthermore, a linear analysis, as well as self-consistent particle simulations of a multipulsed 10 kA beam, indicated that only a negligible small fraction of energy is radiated into nonfundamental cavity modes. Finally, the beam breakup instability is analyzed and found to be able to magnify initial radial perturbations by a factor of no more than about 20 during the beam transit time through a 1 GeV accelerator.

  18. Auroral electron beams - Electric currents and energy sources

    NASA Astrophysics Data System (ADS)

    Kaufmann, R. L.

    1981-09-01

    The energy sources, electric equipotentials and electric currents associated with auroral electron acceleration observed during rocket flight 18:152 are discussed. Steep flow gradients at the interface between the convection boundary layer and the plasma sheet are considered as the probable source of energy for dayside and dawn and dusk auroras, while it is suggested that the cross tail potential drop may provide an energy source for some midnight auroras. Birkeland currents that flow along distorted field lines are shown possibly to be important in the mechanism that produces U-shaped equipotentials in the ionosphere, as well as unexpected jumps in ionospheric or magnetotail currents and unusual electric fields and plasma drift in the magnetotail. The production of equipotential structures under oppositely directed higher-altitude electric fields is discussed, and it is pointed out that cold ionospheric plasma can enter the structure in a cusp-shaped region where fields are weak. The rocket data reveals that the sudden change in conductivity at the edge of the bright arc and the constancy of the electric field produce sudden changes in the Hall and Pedersen currents. It is concluded that current continuity is satisfied primarily by east-west changes in the electric field or conductivity.

  19. Limiting electron beam current for cyclic induction acceleration in a constant guide field

    SciTech Connect

    Kanunnikov, V.N.

    1982-09-01

    Theoretical relations are derived for the limiting beam current in a cyclic induction accelerator (CIA) with a constant guide field. The calculations are in agreement with the available experimental data. It is shown that the limiting average beam current in a CIA is of the order of 100 microamperes, i.e., the level attained in microtrons and linear accelerators. The CIA may find industrial applications.

  20. Neutral beam current driven operation of the DIII-D tokamak

    SciTech Connect

    Simonen, T.C.; Bhadra, D.K.; Burrell, K.H.; Callis, R.W.; Chance, M.S.; Chu, M.S.; Colleraine, A.P.; Greene, J.M.; Groebner, R.J.; Harvey, R.W.; Hill, D.N.; Kim, J.; Lao, L.; Matsuoka, M.; Petersen, P.I.; Porter, G.D.; St. John, H.; Stallard, B.W.; Stambaugh, R.D.; Strait, E.J.; Taylor, T.S.

    1988-03-01

    Neutral beam current drive experiment in the DII-D tokamak with a single null poloidal divertor are described. A plasma current of 0.34 MA has been sustained entirely by neutral beams with H-mode quality energy confinement. Poloidal beta values reach 3.5 without disruption or coherent magnetic activity, suggesting that these plasmas may be entering the second stability regime. 12 refs., 2 figs.

  1. Role of the rise rate of beam current in the microwave radiation of vircator

    NASA Astrophysics Data System (ADS)

    Li, Limin; Cheng, Guoxin; Zhang, Le; Ji, Xiang; Chang, Lei; Xu, Qifu; Liu, Lie; Wen, Jianchun; Li, Chuanlu; Wan, Hong

    2011-04-01

    In this paper, the effect of the rise rate of beam current on the microwave radiation of a virtual cathode oscillator (vircator) is presented. Interestingly, it was observed that the rise rate of the beam current increased as the pulse shot proceeded, which is accompanied by the decrease in microwave power. By comparing the experimental results of two cathode materials (carbon fiber and stainless steel), it was found that the above behavior is independent of the cathode materials. The ion flow, induced by the repetitive action of beam electrons with the anode grid, directly affects the development of beam current. A twice-increased process of ion flow was observed, and there are two factors involved in this process, namely, the reflection of electrons between the cathode and virtual cathode and the effect of one-time bombardment of electron beam. After the irradiation of pulsed electron beam, some microprotrusions toward the cathode appeared on the anode surface, with a quasiperiodic structure. The appearance of ion flow, as the anode plasma forms, increases the beam current and enhances the beam current density. The anode plasma is generated relatively easily as the shot test proceeds, due to the aging of anode grid, which allows the possibility of the decrease in the microwave power. As the pulse shot proceeds, the changes in the rise rate of beam current are closely related to the aging process of anode surface. Therefore, the further enhancement of vircator efficiency needs to lengthen the lifetime of anode, besides the optimization of explosive emission cathodes.

  2. Transverse distribution of beam current oscillations of a 14 GHz electron cyclotron resonance ion source.

    PubMed

    Tarvainen, O; Toivanen, V; Komppula, J; Kalvas, T; Koivisto, H

    2014-02-01

    The temporal stability of oxygen ion beams has been studied with the 14 GHz A-ECR at JYFL (University of Jyvaskyla, Department of Physics). A sector Faraday cup was employed to measure the distribution of the beam current oscillations across the beam profile. The spatial and temporal characteristics of two different oscillation "modes" often observed with the JYFL 14 GHz ECRIS are discussed. It was observed that the low frequency oscillations below 200 Hz are distributed almost uniformly. In the high frequency oscillation "mode," with frequencies >300 Hz at the core of the beam, carrying most of the current, oscillates with smaller amplitude than the peripheral parts of the beam. The results help to explain differences observed between the two oscillation modes in terms of the transport efficiency through the JYFL K-130 cyclotron. The dependence of the oscillation pattern on ion source parameters is a strong indication that the mechanisms driving the fluctuations are plasma effects. PMID:24593488

  3. Instrument for spatially resolved simultaneous measurements of forces and currents in particle beams

    NASA Astrophysics Data System (ADS)

    Spethmann, A.; Trottenberg, T.; Kersten, H.

    2015-01-01

    The article presents a device for spatially resolved and simultaneous measurements of forces and currents in particle beams, especially in beams composed of ions and neutral atoms. The forces are exerted by the impinging beam particles on a plane circular conductive target plate of 20 mm diameter mounted on a pendulum with electromagnetic force compensation. The force measurement in the micronewton range is achieved by electromagnetic compensation by means of static Helmholtz coils and permanent magnets attached to the pendulum. Exemplary measurements are performed in the 1.2 keV beam of a broad beam ion source. The simultaneous measurements of forces and currents onto the same target are compared with each other and with Faraday cup measurements.

  4. Instrument for spatially resolved simultaneous measurements of forces and currents in particle beams.

    PubMed

    Spethmann, A; Trottenberg, T; Kersten, H

    2015-01-01

    The article presents a device for spatially resolved and simultaneous measurements of forces and currents in particle beams, especially in beams composed of ions and neutral atoms. The forces are exerted by the impinging beam particles on a plane circular conductive target plate of 20 mm diameter mounted on a pendulum with electromagnetic force compensation. The force measurement in the micronewton range is achieved by electromagnetic compensation by means of static Helmholtz coils and permanent magnets attached to the pendulum. Exemplary measurements are performed in the 1.2 keV beam of a broad beam ion source. The simultaneous measurements of forces and currents onto the same target are compared with each other and with Faraday cup measurements. PMID:25638122

  5. Instrument for spatially resolved simultaneous measurements of forces and currents in particle beams

    SciTech Connect

    Spethmann, A. Trottenberg, T. Kersten, H.

    2015-01-15

    The article presents a device for spatially resolved and simultaneous measurements of forces and currents in particle beams, especially in beams composed of ions and neutral atoms. The forces are exerted by the impinging beam particles on a plane circular conductive target plate of 20 mm diameter mounted on a pendulum with electromagnetic force compensation. The force measurement in the micronewton range is achieved by electromagnetic compensation by means of static Helmholtz coils and permanent magnets attached to the pendulum. Exemplary measurements are performed in the 1.2 keV beam of a broad beam ion source. The simultaneous measurements of forces and currents onto the same target are compared with each other and with Faraday cup measurements.

  6. Analytical Analysis and Case Study of Transient Behavior of Inrush Current in Power Transformer for Designing of Efficient Circuit Breakers

    NASA Astrophysics Data System (ADS)

    Harmanpreet, Singh, Sukhwinder; Kumar, Ashok; Kaur, Parneet

    2010-11-01

    Stability & security are main aspects in electrical power systems. Transformer protection is major issue of concern to system operation. There are many mall-trip cases of transformer protection are caused by inrush current problems. The phenomenon of transformer inrush current has been discussed in many papers since 1958. In this paper analytical analysis of inrush current in a transformer switched on dc and ac supply has been done. This analysis will help in design aspects of circuit breakers for better performance.

  7. Photorefractive two-beam coupling joint transform correlator: modeling and performance evaluation.

    PubMed

    Nehmetallah, G; Khoury, J; Banerjee, P P

    2016-05-20

    The photorefractive two-beam coupling joint transform correlator combines two features. The first is embedded semi-adaptive optimality, which weighs the correlation against clutter and noise in the input, and the second is the intrinsic dynamic range compression nonlinearity, which improves several metrics simultaneously without metric trade-off. Although the two beam coupling correlator was invented many years ago, its outstanding performance was recognized on only relatively simple images. There was no study about the performance of this correlator on complicated images and using different figures of merit. In this paper, the study is extended to more complicated images. For the first time, to our knowledge, we demonstrate simultaneous improvement in metrics performance without metric trade-off. The performance was evaluated compared to the classical joint transform correlator. A typical experimental result to validate the simulation results was also shown in this work. The best performing operation parameters were identified to guide the experimental work and for future comparison with other well-known optimal correlation filters. PMID:27411127

  8. Impact of quasi-dc currents on three-phase distribution transformer installations

    SciTech Connect

    McConnell, B.W.; Barnes, P.R. ); Tesche, F.M. , Dallas, TX ); Schafer, D.A. )

    1992-06-01

    This report summarizes a series of tests designed to determine the response of quasi-dc currents on three-phase power distribution transformers for electric power systems. In general, if the dc injection is limited to the primary side of a step-down transformer, significant harmonic distortion is noted and an increase in the reactive power demand results. For dc injection on the secondary (load) side of the step-down transformer the harmonic content at the secondary side is quite high and saturation occurs with a relatively low level of dc injection; however, the reactive power demand is significantly lower. These tests produced no apparent damage to the transformers. Transformer damage is dependent on the duration of the dc excitation, the level of the excitation, and on thermal characteristics of the transfer. The transformer response time is found to be much shorter than seen in power transformer tests at lower dc injection levels. This shorter response time suggests that the response time is strongly dependent on the injected current levels, and that higher levels of dc injection for shorter durations could produce very high reactive power demands and harmonic distortion within a few tenths of a second. The added reactive power load could result in the blowing of fuses on the primary side of the transformer for even moderate dc injection levels, and neutral currents are quite large under even low-level dc injection. This smoking neutral'' results in high-level harmonic injection into equipment via the neutral and in possible equipment failure.

  9. Electromagnetic characterization of current transformer with toroidal core under sinusoidal conditions

    NASA Astrophysics Data System (ADS)

    Koprivica, Branko; Milovanovic, Alenka

    2016-04-01

    The aim of this paper is to present a new procedure for the electromagnetic analysis of a measuring current transformer under sinusoidal conditions in its electrical and magnetic circuit. The influence of the magnetic hysteresis has been taken into account using the measured inverse magnetization curve and phase lag between the time waveforms of the magnetic field and the magnetic induction. Using the proposed analysis, ratio and phase errors of the current transformer have been calculated. The results of the calculation have been compared with experimental results and a good agreement has been found.

  10. Low-impedance plasma systems for generation of high-current low-energy electron beams

    NASA Astrophysics Data System (ADS)

    Agafonov, A. V.

    2006-12-01

    The results of experimental investigation and numerical modeling of the generation of low-energy (tens of keV) high-current (up to tens of kA) electron beams in a low-impedance system consisting of a plasma-filled diode with a long plasma anode, an auxiliary hot cathode, and an explosive emission cathode. The low-current low-voltage beam from the auxiliary cathode in an external longitudinal magnetic field is used to produce a long plasma anode, which is simultaneously the channel of beam transportation by residual gas ionization. The high-current electron beam is formed from the explosive emission cathode placed in the preliminarily formed plasma. Numerical modeling is performed using the KARAT PIC code.

  11. Fast neutral beam ion source coupled to a Fourier transform ion cyclotron resonance mass spectrometer

    SciTech Connect

    Hill, N.C.; Limbach, P.A.; Shomo, R.E. II; Marshall, A.G. ); Appelhans, A.D.; Delmore, J.E. )

    1991-11-01

    The coupling of an autoneutralizing SF{sup {minus}}{sub 6} fast ion-beam gun to a Fourier transform ion cyclotron resonance (FT/ICR) mass spectrometer is described. The fast neutral beam provides for secondary-ion-type FT/ICR mass analysis (e.g., production of abundant pseudomolecular (M+H){sup +} ions) of involatile samples without the need for external ion injection, since ions are formed at the entrance to the ICR ion trap. The design, construction, and testing of the hybrid instrument are described. The feasibility of the experiment (for both broadband and high-resolution FT/ICR positive-ion mass spectra) is demonstrated with {ital tetra}-butylammonium bromide and a Tylenol{sup ( )} sample. The ability to analyze high molecular weight polymers with high mass resolution is demonstrated for Teflon{sup ( )}. All of the advantages of the fast neutral beam ion source previously demonstrated with quadrupole mass analysis are preserved, and the additional advantages of FT/ICR mass analysis (e.g., high mass resolving power, ion trapping) are retained.

  12. Fast neutral beam ion source coupled to a Fourier transform ion cyclotron resonance mass spectrometer

    NASA Astrophysics Data System (ADS)

    Hill, Nicholas C.; Limbach, Patrick A.; Shomo, Ronald E., II; Marshall, Alan G.; Appelhans, Anthony D.; Delmore, James E.

    1991-11-01

    The coupling of an autoneutralizing SF-6 fast ion-beam gun to a Fourier transform ion cyclotron resonance (FT/ICR) mass spectrometer is described. The fast neutral beam provides for secondary-ion-type FT/ICR mass analysis [e.g., production of abundant pseudomolecular (M+H)+ ions] of involatile samples without the need for external ion injection, since ions are formed at the entrance to the ICR ion trap. The design, construction, and testing of the hybrid instrument are described. The feasibility of the experiment (for both broadband and high-resolution FT/ICR positive-ion mass spectra) is demonstrated with tetra-butylammonium bromide and a Tylenol■ sample. The ability to analyze high molecular weight polymers with high mass resolution is demonstrated for Teflon■. All of the advantages of the fast neutral beam ion source previously demonstrated with quadrupole mass analysis are preserved, and the additional advantages of FT/ICR mass analysis (e.g., high mass resolving power, ion trapping) are retained.

  13. Current Control in ITER Steady State Plasmas With Neutral Beam Steering

    SciTech Connect

    R.V. Budny

    2009-09-10

    Predictions of quasi steady state DT plasmas in ITER are generated using the PTRANSP code. The plasma temperatures, densities, boundary shape, and total current (9 - 10 MA) anticipated for ITER steady state plasmas are specified. Current drive by negative ion neutral beam injection, lower-hybrid, and electron cyclotron resonance are calculated. Four modes of operation with different combinations of current drive are studied. For each mode, scans with the NNBI aimed at differing heights in the plasma are performed to study effects of current control on the q profile. The timeevolution of the currents and q are calculated to evaluate long duration transients. Quasi steady state, strongly reversed q profiles are predicted for some beam injection angles if the current drive and bootstrap currents are sufficiently large.

  14. RESULTS OF BEAM TESTS ON A HIGH CURRENT EBIS TEST STAND.

    SciTech Connect

    BEEBE,E.; ALESSI,J.; BELLAVIA,S.; HERSHCOVITCH,A.; KPONOU,A.; LOCKEY,R.; PIKIN,A.; PRELEC,K.; KUZNETSOV,G.; TIUNOV,M.

    1999-03-29

    At Brookhaven National Laboratory there is an R&D program to design an Electron Beam Ion Source (EBIS) for use in a compact ion injector to be developed for the relativistic heavy ion collider (RHIC). The BNL effort is directed at developing an EBIS with intensities of 3 x 10{sup 9} particles/pulse of ions such as Au{sup 35+} and U{sup 45+}, and requires an electron beam on the order of 10A. The construction of a test stand (EBTS) with the full electron beam power and 1/3 the length of the EBIS for RHIC is nearing completion. Initial commissioning of the EBTS was made with pulsed electron beams of duration < 1ms and current up to 13 A. Details of the EBTS construction, results of the pulse tests, and preparations for DC electron beam tests are presented.

  15. Emittance growth from charge density changes in high-current beams

    SciTech Connect

    Wangler, T.P.; Crandall, K.R.; Mills, R.S.

    1986-01-21

    We use the relation between field energy and rms emittance, together with the property of charge-density homogenization for intense nonuniform beams in linear focusing systems, to derive equations for emittance growth and minimum final emittance. We discuss three problems in which this charge redistribution mechnism is isolated: the 1-D continuous sheet beam, the 2-D continuous round beam, and the 3-D spherical bunch. For each of the three problems, we identify and compare scaling parameters tha determine the emittance growth and minimum final emittance as a function of beam current, emittance, and external focusing strength. Numerical simulations are used to test the equations, to show that the charge redistribution mechanism results in very rapid emittance growth, and to study the detailed time evolution of the beams.

  16. HIGH AVERAGE CURRENT LOW EMITTANCE BEAM EMPLOYING CW NORMAL CONDUCTING GUN.

    SciTech Connect

    CHANG,X.; BEN-ZVI, I.; KEWISCH, J.; PAI, C.

    2007-06-25

    CW normal conducting guns usually do not achieve very high field gradient and waste much RF power at high field gradient compared to superconducting cavities. But they have less trapped modes and wakefields compared to the superconducting cavities due to their low Q. The external bucking coil can also be applied very close to the cathode to improve the beam quality. By using a low frequency gun with a recessed cathode and a carefully designed beam line we can get a high average current and a high quality beam with acceptable RF power loss on the cavity wall. This paper shows that the CW normal conducting gun can be a backup solution for those projects which need high peak and average current, low emittance electron beams such as the Relativistic Heavy Ion Collider (RHIC) e-cooling project and Energy Recovery Linac (Em) project.

  17. Recirculation acceleration of high current relativistic electron beams--a feasibility study. Final report

    SciTech Connect

    Wilson, M.

    1981-06-01

    One of the advanced accelerator concepts under study at NBS involves multiplying the energy gained by a long-pulse, high current relativistic electron beam by directing the beam several times through the same induction accelerator during the time of one voltage pulse. Should this concept of the recirculation acceleration of intense electron beams be proven feasible, the savings in cost, size, and weight of a high current accelerator would be considerable. Energy gain by recirculation acceleration through a small-scale proof-of principle facility has been demonstrated at NBS. The study employs a 750A, 750keV electron beam pulse, 2 microsec long, generated by a linear induction accelerator of unique design which was also developed at NBS.

  18. Mapping of ion beam induced current changes in FinFETs

    SciTech Connect

    Weis, C. D.; Schuh, A.; Batra, A.; Persaud, A.; Rangelow, I. W.; Bokor, J.; Lo, C. C.; Cabrini, S.; Olynick, D.; Duhey, S.; Schenkel, T.

    2008-09-30

    We report on progress in ion placement into silicon devices with scanning probealignment. The device is imaged with a scanning force microscope (SFM) and an aligned argon beam (20 keV, 36 keV) is scanned over the transistor surface. Holes in the lever of the SFM tip collimate the argon beam to sizes of 1.6 mu m and 100 nm in diameter. Ion impacts upset the channel current due to formation of positive charges in the oxide areas. The induced changes in the source-drain current are recorded in dependence of the ion beam position in respect to the FinFET. Maps of local areas responding to the ion beam are obtained.

  19. The effect of beam-driven return current instability on solar hard X-ray bursts

    NASA Technical Reports Server (NTRS)

    Cromwell, D.; Mcquillan, P.; Brown, J. C.

    1986-01-01

    The problem of electrostatic wave generation by a return current driven by a small area electron beam during solar hard X-ray bursts is discussed. The marginal stability method is used to solve numerically the electron and ion heating equations for a prescribed beam current evolution. When ion-acoustic waves are considered, the method appears satisfactory and, following an initial phase of Coulomb resistivity in which T sub e/T sub i rise, predicts a rapid heating of substantial plasma volumes by anomalous ohmic dissipation. This hot plasma emits so much thermal bremsstrahlung that, contrary to previous expectations, the unstable beam-plasma system actually emits more hard X-rays than does the beam in the purely collisional thick target regime relevant to larger injection areas. Inclusion of ion-cyclotron waves results in ion-acoustic wave onset at lower T sub e/T sub i and a marginal stability treatment yields unphysical results.

  20. Analysis of longitudinal beam dynamics behavior and rf system operative limits at high-beam currents in storage rings

    NASA Astrophysics Data System (ADS)

    Mastorides, T.; Rivetta, C.; Fox, J. D.; van Winkle, D.; Teytelman, D.

    2008-06-01

    A dynamics simulation model is used to estimate limits of performance of the positron-electron project (PEP-II). The simulation captures the dynamics and technical limitations of the low level radio frequency (LLRF) system, the high-power rf components, and the low-order mode coupled-bunch longitudinal beam dynamics. Simulation results showing the effect of nonlinearities on the LLRF loops, and studies of the effectiveness of technical component upgrades are reported, as well as a comparison of these results with PEP-II measurements. These studies have led to the estimation of limits and determining factors in the maximum stored current that the low energy ring/high energy ring (LER/HER) can achieve, based on system stability for different rf station configurations and upgrades. In particular, the feasibility of the PEP-II plans to achieve the final goal in luminosity, which required an increase of the beam currents to 4 A for LER and 2.2 A for HER, is studied. These currents are challenging in part because they would push the longitudinal low-order beam mode stability to the limit, and the klystron forward power past a level of satisfactory margin. An acceptable margin is defined in this paper, which in turn determines the corresponding klystron forward power limitation.

  1. Ion beam-induced amorphous-to-tetragonal phase transformation and grain growth of nanocrystalline zirconia

    SciTech Connect

    Lian, Jie; Zhang, Jiaming; Namavar, Fereydoon; Zhang, Yanwen; Lu, Fengyuan; Haider, Hani; Garvin, Kevin; Weber, William J.; Ewing, Rodney C.

    2009-05-26

    Nanocrystalline zirconia has recently attracted extensive research interest due to its unique mechanical, thermal and electrical properties as compared to bulk zirconia counterparts, and it is of particular importance to control the phase stability of different polymorphs (amorphous, cubic, tetragonal and monoclinic phases) at different size regimes. In this paper, we performed ion beam bombardments on bilayers (amorphous and cubic) of pure nano-zirconia using 1 MeV Kr2+ irradiation. Transmission electron microscopy (TEM) analysis reveals that amorphous zirconia transforms to a tetragonal structure under irradiation at room temperature, suggesting that the tetragonal phase is more energetically favorable under these conditions. The final grain size of the tetragonal zirconia can be controlled by irradiation conditions. The irradiation-induced nanograins of tetragonal ZrO2 are stable at ambient conditions and maintain their physical integrity over a long period of time after irradiation. These results demonstrated that ion-beam modification methods provide the means to control the phase stability and structure of zirconia polymorphs.

  2. Coherent beam control with an all-dielectric transformation optics based lens

    NASA Astrophysics Data System (ADS)

    Yi, Jianjia; Burokur, Shah Nawaz; Piau, Gérard-Pascal; de Lustrac, André

    2016-01-01

    Transformation optics (TO) concept well known for its huge possibility in patterning the path of electromagnetic waves is exploited to design a beam steering lens. The broadband directive in-phase emission in a desired off-normal direction from an array of equally fed radiators is numerically and experimentally reported. Such manipulation is achieved without the use of complex and bulky phase shifters as it is the case in classical phased array antennas. The all-dielectric compact low-cost lens prototype presenting a graded permittivity profile is fabricated through three-dimensional (3D) polyjet printing technology. The array of radiators is composed of four planar microstrip antennas realized using standard lithography techniques and is used as excitation source for the lens. To validate the proposed lens, we experimentally demonstrate the broadband focusing properties and in-phase directive emissions deflected from the normal direction. Both the far-field radiation patterns and the near-field distributions are measured and reported. Measurements agree quantitatively and qualitatively with numerical full-wave simulations and confirm the corresponding steering properties. Such experimental validation paves the way to inexpensive easy-made all-dielectric microwave lenses for beam forming and collimation.

  3. Coherent beam control with an all-dielectric transformation optics based lens

    PubMed Central

    YI, Jianjia; Burokur, Shah Nawaz; Piau, Gérard-Pascal; de Lustrac, André

    2016-01-01

    Transformation optics (TO) concept well known for its huge possibility in patterning the path of electromagnetic waves is exploited to design a beam steering lens. The broadband directive in-phase emission in a desired off-normal direction from an array of equally fed radiators is numerically and experimentally reported. Such manipulation is achieved without the use of complex and bulky phase shifters as it is the case in classical phased array antennas. The all-dielectric compact low-cost lens prototype presenting a graded permittivity profile is fabricated through three-dimensional (3D) polyjet printing technology. The array of radiators is composed of four planar microstrip antennas realized using standard lithography techniques and is used as excitation source for the lens. To validate the proposed lens, we experimentally demonstrate the broadband focusing properties and in-phase directive emissions deflected from the normal direction. Both the far-field radiation patterns and the near-field distributions are measured and reported. Measurements agree quantitatively and qualitatively with numerical full-wave simulations and confirm the corresponding steering properties. Such experimental validation paves the way to inexpensive easy-made all-dielectric microwave lenses for beam forming and collimation. PMID:26729400

  4. Coherent beam control with an all-dielectric transformation optics based lens.

    PubMed

    Yi, Jianjia; Burokur, Shah Nawaz; Piau, Gérard-Pascal; de Lustrac, André

    2016-01-01

    Transformation optics (TO) concept well known for its huge possibility in patterning the path of electromagnetic waves is exploited to design a beam steering lens. The broadband directive in-phase emission in a desired off-normal direction from an array of equally fed radiators is numerically and experimentally reported. Such manipulation is achieved without the use of complex and bulky phase shifters as it is the case in classical phased array antennas. The all-dielectric compact low-cost lens prototype presenting a graded permittivity profile is fabricated through three-dimensional (3D) polyjet printing technology. The array of radiators is composed of four planar microstrip antennas realized using standard lithography techniques and is used as excitation source for the lens. To validate the proposed lens, we experimentally demonstrate the broadband focusing properties and in-phase directive emissions deflected from the normal direction. Both the far-field radiation patterns and the near-field distributions are measured and reported. Measurements agree quantitatively and qualitatively with numerical full-wave simulations and confirm the corresponding steering properties. Such experimental validation paves the way to inexpensive easy-made all-dielectric microwave lenses for beam forming and collimation. PMID:26729400

  5. High current proton beams production at Simple Mirror Ion Source 37.

    PubMed

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

    2014-02-01

    This paper presents the latest results of high current proton beam production at Simple Mirror Ion Source (SMIS) 37 facility at the Institute of Applied Physics (IAP RAS). In this experimental setup, the plasma is created and the electrons are heated by 37.5 GHz gyrotron radiation with power up to 100 kW in a simple mirror trap fulfilling the ECR condition. Latest experiments at SMIS 37 were performed using a single-aperture two-electrode extraction system. Proton beams with currents up to 450 mA at high voltages below 45 kV were obtained. The maximum beam current density was measured to be 600 mA/cm(2). A possibility of further improvement through the development of an advanced extraction system is discussed. PMID:24593436

  6. Current-voltage relation for a field ionizing He beam detector

    SciTech Connect

    DePonte, D. P.; Elliott, Greg S.; Kevan, S. D.

    2009-02-15

    Emerging interest in utilizing the transverse coherence properties of thermal energy atomic and molecular beams motivates the development of ionization detectors with near unit detection efficiency and adequate spatial resolution to resolve interference fringes of submicron dimension. We demonstrate that a field ionization tip coupled to a charged particle detector meets these requirements. We have systematically studied the current-voltage relationship for field ionization of helium using tungsten tips in diffuse gas and in a supersonic helium beam. For all 16 tips used in this study, the dependence of ion current on voltage for tips of fixed radius was found to differ from that for tips held at constant surface electric field. A scaling analysis is presented to explain this difference. Ion current increased on average to the 2.8 power of voltage for a tip at fixed field and approximately fifth power of voltage for fixed radius for a liquid nitrogen cooled tip in room temperature helium gas. For the helium beam, ion current increased as 2.2 power of voltage with constant surface field. The capture region of the tips was found to be up to 0.1 {mu}m{sup 2} for diffuse gas and 0.02 {mu}m{sup 2} in the beam. Velocity dependence and orientation of tip to beam were also studied.

  7. Theory of beam induced current characterization of grain boundaries in polycrystalline solar cells

    NASA Astrophysics Data System (ADS)

    Donolato, C.

    1983-03-01

    A theoretical analysis is given of the induced current profiles at grain boundaries in polycrystalline solar cells, as obtained by light or electron beam excitation. The area A and the variance sigma-squared of the contrast profile of a grain boundary are calculated for realistic generations as functions of the interface recombination velocity v(s) and the minority carrier diffusion length L. A new graphical procedure is proposed which allows the simultaneous determination of v(s) and L from the measured values of A and sigma. The evaluation of an experimental electron beam-induced current profile illustrates the applicability of the theory.

  8. Hilbert versus Concordia transform for three-phase machine stator current time-frequency monitoring

    NASA Astrophysics Data System (ADS)

    Trajin, Baptiste; Chabert, Marie; Regnier, Jérémi; Faucher, Jean

    2009-11-01

    This paper deals with mechanical fault diagnosis in three-phase induction machines from stator current measurements. According to machine models, mechanical faults lead to amplitude and/or phase modulations of the measured stator current with possibly time varying carrier frequency. The modulation diagnosis requires a univocal definition of the instantaneous phase and amplitude. This is performed by associating a complex signal to the real measured one. For a convenient separate modulation diagnosis, the complex signal instantaneous phase and amplitude are expected to carry, respectively, information about the phase and amplitude modulations. The complex signal is classically obtained through the Hilbert transform. Under Bedrosian conditions, the so-called analytic signal allows a separate modulation diagnosis. However, mechanical faults may also produce fast modulations violating the Bedrosian conditions. This study proposes an alternative complex signal representation which takes advantage of the three stator current measurements available in a three-phase machine. From two stator current measurements, the Concordia transform builds a complex vector, the so-called space vector, which unconditionally allows separate modulation diagnosis. This paper applies and compares the Hilbert and Concordia transforms, theoretically and in case of simulated and experimental signals with various modulation frequency ranges.

  9. A Four Channel Beam Current Monitor Data Acquisition System Using Embedded Processors

    SciTech Connect

    Wheat, Jr., Robert Mitchell; Dalmas, Dale A.; Dale, Gregory E.

    2015-08-11

    Data acquisition from multiple beam current monitors is required for electron accelerator production of Mo-99. A two channel system capable of recording data from two beam current monitors has been developed, is currently in use, and is discussed below. The development of a cost-effective method of extending this system to more than two channels and integrating of these measurements into an accelerator control system is the main focus of this report. Data from these current monitors is digitized, processed, and stored by a digital data acquisition system. Limitations and drawbacks with the currently deployed digital data acquisition system have been identified as have been potential solutions, or at least improvements, to these problems. This report will discuss and document the efforts we've made in improving the flexibility and lowering the cost of the data acquisition system while maintaining the minimum requirements.

  10. Characterization of the beam transmission improvements for p- and n-LDD implantations on a single wafer high current spot beam implanter

    NASA Astrophysics Data System (ADS)

    Schmeide, Matthias; Kondratenko, Serguei; Deichler, Josef

    2012-11-01

    This paper focuses on the characterization of the biased beam guide option installed in the 200 mm Axcelis Optima HDx single wafer high current spot beam implanter and its use for energy contamination free, drift mode p-LDD and n-LDD implantations. Biased beam guide mode allows reduction of space charge potential and corresponding transmission loss from beam blow up, resulting in horizontally and vertically smaller ion beams. Smaller, highly focused beams have several advantages, such as improved beam transmission, higher dose rate, and require reduced overscan area. Higher beam transmission and higher beam current combined with reduced overscan are two factors that directly affect throughput and productivity. We demonstrate these improvements for several important logic processes. A characterization of the effects of beam guide bias voltage for a 90 nm CMOS logic is reported in detail. The p-LDD and n-LDD implantations investigated were BF2+, As+, and As2+ in the energy range between 3 keV and 5 keV, both with and without Germanium pre-amorphization. The presented and discussed results include beam parameters, throughput results, beam setup performance, and device data. The results have shown that the biased beam guide mode can significantly improve the throughput for the LDD implantations in the energy range of interest.

  11. Current status and future prospect of electron beam sterilization in Japan

    NASA Astrophysics Data System (ADS)

    Katsura, Ichiro

    1998-06-01

    It seems that electron beam sterilization is being current topic among all applications in Japan and that this tendency will continue until when major companies interested in the technology complete introducing electron beam. Since the Ministry of Health and Welfare(MOHW) officially issued revised regulation on GMP for medical devices in 1995, EtO has become the method regarded as time and money consuming one. On the contrary, electron beam has become as relatively economical and desirable method to achieve same result by its characteristics such as high productivity, rather easy validation and consequent cost reduction, although less penetration limit the kind of products to be treated. Status and prospect of electron beam sterilization in Japan will be presented in the paper along with accelerator related technologies.

  12. Modulation of auroral electrojet currents using dual HF beams with ELF phase offset

    NASA Astrophysics Data System (ADS)

    Golkowski, M.; Cohen, M.; Moore, R. C.

    2012-12-01

    The modulation of naturally occuring ionospheric currents with high power radio waves in the high frequency (HF, 3-10 MHz) band is a well known technique for generation of extremely low frequency (ELF, 3-3000 Hz) and very low frequency (VLF, 3-30 kHz) waves. We use the heating facility of the High Frequency Active Auroral Research Program (HAARP) to investigate the effect of using dual HF beams with an ELF/VLF phase offset between the modulation waveforms. Experiments with offset HF beams confirm the model of independent ELF/VLF sources. Experiments with co-located HF beams exhibit interaction between the first and second harmonics of the modulated tones when square and sine wave modulation waveforms are employed. Using ELF/VLF phase offsets for co-loacted beams is also shown to be a potential diagnostic for the D-region ionospheric profile.

  13. A detector based on silica fibers for ion beam monitoring in a wide current range

    NASA Astrophysics Data System (ADS)

    Auger, M.; Braccini, S.; Carzaniga, T. S.; Ereditato, A.; Nesteruk, K. P.; Scampoli, P.

    2016-03-01

    A detector based on doped silica and optical fibers was developed to monitor the profile of particle accelerator beams of intensity ranging from 1 pA to tens of μA. Scintillation light produced in a fiber moving across the beam is measured, giving information on its position, shape and intensity. The detector was tested with a continuous proton beam at the 18 MeV Bern medical cyclotron used for radioisotope production and multi-disciplinary research. For currents from 1 pA to 20 μA, Ce3+ and Sb3+ doped silica fibers were used as sensors. Read-out systems based on photodiodes, photomultipliers and solid state photomultipliers were employed. Profiles down to the pA range were measured with this method for the first time. For currents ranging from 1 pA to 3 μA, the integral of the profile was found to be linear with respect to the beam current, which can be measured by this detector with an accuracy of ~1%. The profile was determined with a spatial resolution of 0.25 mm. For currents ranging from 5 μA to 20 μA, thermal effects affect light yield and transmission, causing distortions of the profile and limitations in monitoring capabilities. For currents higher than ~1 μA, non-doped optical fibers for both producing and transporting scintillation light were also successfully employed.

  14. Evaluation of conductor stresses in a pulsed high-current toroidal transformer

    SciTech Connect

    Turchi, Peter J; Rousculp, Chritopher L; Reass, William A; Oro, David M; Merrill, Frank E; Greigo, Jeffery R; Reinovsky, Robert E

    2009-01-01

    The Precision, High-Energy Density, Liner Implosion Experiment (PHELIX) pulsed power driver is currently under development at Los Alamos National Laboratory. When operational PHELIX will provide 5-10 MAmps of peak current with pulse rise-time of {approx} 5-10 ms. Crucial to the performance of PHELIX is a multi-turn primary, single-turn secondary, current step-up toroidal transformer, R{sub major} {approx} 30 cm, R{sub minor} {approx} 10 cm. The transformer lifetime should exceed 100 shots. Therefore it is essential that the design be robust enough to survive the magnetic stresses produced by high currents. In order to evaluate their design, two methods have been utilized. First, an analytical evaluation has been performed. By identifying the magnetic forces as J{sub 1}{sup 2}/2 {del}L{sub 1} + J{sub 1}J{sub 2}{del}M{sub 12}, where J{sub 1} and J{sub 2} are currents in two circuits, coupled by mutual inductance M{sub 12} and L{sub 1} is the self-inductance of the circuit carrying current J{sub 1}, analytical estimates of stress can be obtained. These results are then compared to a computational MHD model of the same system and to a full finite-element, electromagnetic simulation.

  15. Phase transformation studies in unirradiated and proton beam irradiated Ni-Ti alloy between 25 and 100°C

    NASA Astrophysics Data System (ADS)

    Ayub, Rana; Afzal, Naveed; Ahmad, R.

    2012-06-01

    The stress-induced phase transformation characteristics of unirradiated and proton beam irradiated NiTi alloy were investigated at different tests temperatures. The wire-shaped NiTi specimens were irradiated by 2 MeV proton beam for 30 min at room temperature to a flux of 1019 protons/m2 s. Engineering stress-strain (S-S) curves of both unirradiated and irradiated specimens were obtained using a materials testing machine at 25, 50, 75 and 100°C. The results indicate a single-stage phase transformation from austenite to martensite (B2-B19‧) in unirraidated specimens at all the test temperatures. In contrast, in the case of the irradiated specimens, a two-stage austenite-rhombohedral-martensite (B2-R-B19‧) phase transformation is observed at 25 and 50°C. The B2-R-B19‧ phase transformation, however, is found to change into B2-B19‧ transformation at 75 and 100°C. The stress required to initiate the B19‧ phase transformation (σMS) and the plateau range are found to be lower in irradiated specimens compared with those of the unirradiated specimens. The results obtained are discussed on the basis of the formation of Ni4Ti3 precipitates in irradiated specimens and their consequences on the phase transformations.

  16. Limiting current enhancements for a relativistic electron beam propagating through coaxial cylinders

    SciTech Connect

    Baedke, W. C.

    2009-09-15

    An investigation of the space-charge-limited (SCL) currents for un-neutralized relativistic electron beams drifting through an infinitely long dielectrically lined coaxial cylindrical structure with a biased inner conductor is presented. To begin, an approximate limiting current expression is developed for an un-neutralized finite-width relativistic electron beam drifting through a biased coaxial cylindrical structure, which contains no dielectric liner. The SCL currents are then numerically calculated and compared to the approximation and it is shown that there is good agreement between the two. Building on this, the SCL currents are then numerically calculated when a dielectric liner, which encloses the finite-width electron beam, is present. It is shown that when a dielectric liner is present, there is a point at which increases in the SCL currents saturate and increasing the relative dielectric constant provides no additional increase in the expected SCL currents. In addition, it is demonstrated that the dielectric liner, in conjunction with the biased inner conductor, provides significant SCL current enhancements when compared to a system with no dielectric liner and no biased inner conductor. Finally, the possibility of dielectric breakdown is addressed as well as the amount of accumulated charge at the vacuum-dielectric interface.

  17. Current transformer model with hysteresis for improving the protection response in electrical transmission systems

    NASA Astrophysics Data System (ADS)

    Matussek, Robert; Dzienis, Cezary; Blumschein, Jörg; Schulte, Horst

    2014-12-01

    In this paper, a generic enhanced protection current transformer (CT) model with saturation effects and transient behavior is presented. The model is used for the purpose of analysis and design of power system protection algorithms. Three major classes of protection CT have been modeled which all take into account the nonlinear inductance with remanence effects. The transient short-circuit currents in power systems are simulated under CT saturation condition. The response of a common power system protection algorithm with respect to robustness to nominal parameter variations and sensitivity against maloperation is demonstrated by simulation studies.

  18. Control and readout of current-induced magnetic flux quantization in a superconducting transformer

    NASA Astrophysics Data System (ADS)

    Kerner, C.; Hackens, B.; Golubović, D. S.; Poli, S.; Faniel, S.; Magnus, W.; Schoenmaker, W.; Bayot, V.; Maes, H.

    2009-02-01

    We demonstrate a simple and robust method for inducing and detecting changes of magnetic flux quantization in the absence of an externally applied magnetic field. In our device, an isolated ring is interconnected with two access loops via permalloy cores, forming a superconducting transformer. By applying and tuning a direct current at the first access loop, the number of flux quanta trapped in the isolated ring is modified without the aid of an external field. The flux state of the isolated ring is simply detected by recording the evolution of the critical current of the second access loop.

  19. Low leakage current gate dielectrics prepared by ion beam assisted deposition for organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Chang Su; Jo, Sung Jin; Kim, Jong Bok; Ryu, Seung Yoon; Noh, Joo Hyon; Baik, Hong Koo; Lee, Se Jong; Kim, Youn Sang

    2007-12-01

    This communication reports on the fabrication of low operating voltage pentacene thin-film transistors with high-k gate dielectrics by ion beam assisted deposition (IBAD). These densely packed dielectric layers by IBAD show a much lower level of leakage current than those created by e-beam evaporation. These results, from the fact that those thin films deposited with low adatom mobility, have an open structure, consisting of spherical grains with pores in between, that acts as a significant path for leakage current. By contrast, our results demonstrate the potential to limit this leakage. The field effect mobility, on/off current ratio, and subthreshold slope obtained from pentacene thin-film transistors (TFTs) were 1.14 cm2/V s, 105, and 0.41 V/dec, respectively. Thus, the high-k gate dielectrics obtained by IBAD show promise in realizing low leakage current, low voltage, and high mobility pentacene TFTs.

  20. A squid-based beam current monitor for FAIR/CRYRING

    NASA Astrophysics Data System (ADS)

    Geithner, Rene; Kurian, Febin; Reeg, Hansjörg; Schwickert, Marcus; Neubert, Ralf; Seidel, Paul; Stöhlker, Thomas

    2015-11-01

    A SQUID-based beam current monitor was developed for the upcoming FAIR-Project, providing a non-destructive online monitoring of the beam currents in the nA-range. The cryogenic current comparator (CCC) was optimized for lowest possible noise-limited current resolution together with a high system bandwidth. This CCC is foreseen to be installed in the CRYRING facility (CRYRING@ESR: A study group report www.gsi.de/fileadmin/SPARC/documents/Cryring/ReportCryring_40ESR.PDF), working as a test bench for FAIR. In this contribution we present results of the completed CCC for FAIR/CRYRING and also arrangements that have been done for the installation of the CCC at CRYRING, regarding the cryostat design.

  1. Analysis of misoperation of the differential current relay applied in a Y-Y-Y-{Delta} transformer

    SciTech Connect

    Wang, F.; Tang, J.

    1995-09-01

    Transformers play an important role in power transmission and distribution systems. For the operation of transformers, the differential current relay is the most important kind of relay in transformer protective relays in present power system.s In principle, a differential current relay may safely and quickly remove the internal fault occurring inside a transformer and in the feeder between the transformer and the busbar within the range of protection. When an external fault happens outside of the transformer, the relay should be reliably locked to ensure that the protected transformer can normally operate. However, because transformers have many different structures and winding connections forms, especially some specially winding-connected transformers, misconnection of the differential current relay may happen in some circumstances. When an external fault occurs, the relay connected in the incorrect way may cause misoperation of the relay, enlarging the range of the system fault. This paper illustrates a misoperation of a set of differential relays applied in a special multi-winding transformer, with triple-Y-connected windings and an additional delta-connected winding, due to the misconnection of the relays in field. An analysis of the difference of the equivalent circuits between the triple-Y-connected winding transformer and the triple-Y-connected winding with an additional delta-connected winding transformer is presented. Some measures to prevent those mistakes are discussed in this paper.

  2. Discharge current and current of supershort avalanche E-beam at volume nanosecond discharge in non-uniform electric field

    NASA Astrophysics Data System (ADS)

    Tarasenko, Victor F.; Rybka, Dmitrii V.; Baksht, Evgenii H.; Kostyrya, Igor'D.; Lomaev, Mikhail I.

    2008-01-01

    The gas diode current-voltage characteristics at the voltage pulses applied from the RADAN and SM-3NS pulsers, and generation of an supershort avalanche electron beam (SAEB) have been studied experimentally in an inhomogeneous electric field upon a nanosecond breakdown in an air gap at atmospheric pressure. Displacement currents with amplitude over 1 kA have been observed and monitored. It is shown that the displacement current amplitude gets increased due to movement of the dense plasma front and charging of a "capacitor" formed between plasma and anode. The SAEB generation time relatively to the discharge current pulses and the gap voltage were determined in the experiments. It is shown that the SAEB current maximum at the pulser voltages of hundreds kV is registered on the discharge current pulse front, before the discharge current peak of the gas diode capacitance, and the delay time of these peaks is determined by the value of an interelectrode spacing. The delay time in case of a gap of 16 mm and air breakdown at atmospheric pressure was ~100 ps, and in case of 10 mm it was less than 50 ps.

  3. Propagation, beam geometry, and detection distortions of peak shapes in two-dimensional Fourier transform spectra.

    PubMed

    Yetzbacher, Michael K; Belabas, Nadia; Kitney, Katherine A; Jonas, David M

    2007-01-28

    Using a solution of Maxwell's equations in the three-dimensional frequency domain, femtosecond two-dimensional Fourier transform (2DFT) spectra that include distortions due to phase matching, absorption, dispersion, and noncollinear excitation and detection of the signal are calculated for Bloch, Kubo, and Brownian oscillator relaxation models. For sample solutions longer than a wavelength, the resonant propagation distortions are larger than resonant local field distortions by a factor of approximately L/lambda, where L is the sample thickness and lambda is the optical wavelength. For the square boxcars geometry, the phase-matching distortion is usually least important, and depends on the dimensionless parameter, L sin(2)(beta)Deltaomega/(nc), where beta is the half angle between beams, n is the refractive index, c is the speed of light, and Deltaomega is the width of the spectrum. Directional filtering distortions depend on the dimensionless parameter, [(Deltaomega)w(0) sin(beta)/c](2), where w(0) is the beam waist at the focus. Qualitatively, the directional filter discriminates against off diagonal amplitude. Resonant absorption and dispersion can distort 2D spectra by 10% (20%) at a peak optical density of 0.1 (0.2). Complicated distortions of the 2DFT peak shape due to absorption and dispersion can be corrected to within 10% (15%) by simple operations that require knowledge only of the linear optical properties of the sample and the distorted two-dimensional spectrum measured at a peak optical density of up to 0.5 (1). PMID:17286491

  4. Propagation, beam geometry, and detection distortions of peak shapes in two-dimensional Fourier transform spectra

    NASA Astrophysics Data System (ADS)

    Yetzbacher, Michael K.; Belabas, Nadia; Kitney, Katherine A.; Jonas, David M.

    2007-01-01

    Using a solution of Maxwell's equations in the three-dimensional frequency domain, femtosecond two-dimensional Fourier transform (2DFT) spectra that include distortions due to phase matching, absorption, dispersion, and noncollinear excitation and detection of the signal are calculated for Bloch, Kubo, and Brownian oscillator relaxation models. For sample solutions longer than a wavelength, the resonant propagation distortions are larger than resonant local field distortions by a factor of ˜L/λ, where L is the sample thickness and λ is the optical wavelength. For the square boxcars geometry, the phase-matching distortion is usually least important, and depends on the dimensionless parameter, Lsin2(β )Δω/(nc), where β is the half angle between beams, n is the refractive index, c is the speed of light, and Δω is the width of the spectrum. Directional filtering distortions depend on the dimensionless parameter, [(Δω )w0sin(β)/c]2, where w0 is the beam waist at the focus. Qualitatively, the directional filter discriminates against off diagonal amplitude. Resonant absorption and dispersion can distort 2D spectra by 10% (20%) at a peak optical density of 0.1 (0.2). Complicated distortions of the 2DFT peak shape due to absorption and dispersion can be corrected to within 10% (15%) by simple operations that require knowledge only of the linear optical properties of the sample and the distorted two-dimensional spectrum measured at a peak optical density of up to 0.5 (1).

  5. Spatially-Resolved Beam Current and Charge-State Distributions for the NEXT Ion Engine

    NASA Technical Reports Server (NTRS)

    Pollard, James E.; Diamant, Kevin D.; Crofton, Mark W.; Patterson, Michael J.; Soulas, George C.

    2010-01-01

    Plume characterization tests with the 36-cm NEXT ion engine are being performed at The Aerospace Corporation using engineering-model and prototype-model thrusters. We have examined the beam current density and xenon charge-state distribution as functions of position on the accel grid. To measure the current density ratio j++/j+, a collimated Eprobe was rotated through the plume with the probe oriented normal to the accel electrode surface at a distance of 82 cm. The beam current density jb versus radial position was measured with a miniature planar probe at 3 cm from the accel. Combining the j++/j+ and jb data yielded the ratio of total Xe+2 current to total Xe+1 current (J++/J+) at forty operating points in the standard throttle table. The production of Xe+2 and Xe+3 was measured as a function of propellant utilization to support performance and lifetime predictions for an extended throttle table. The angular dependence of jb was measured at intermediate and far-field distances to assist with plume modeling and to evaluate the thrust loss due to beam divergence. Thrust correction factors were derived from the total doubles-to-singles current ratio and from the far-field divergence data

  6. Research on small signal detection of optical voltage/current transformer

    NASA Astrophysics Data System (ADS)

    Li, Hongbo; Zhang, Guoqing; Cai, Xingguo; Guo, Zhizhong; Yu, Wenbin; Huo, Guangyu

    2013-08-01

    This paper researches the signal conditioning program of optical voltage/current transformer and the imbalance during the transmission of dual optical path, gives a brief introduction to the basic principle of optical voltage transformer based on electro-optic Pockels effect and optical current transformer based on Faraday Magnetic-optical Effect, and induces a general expression form of output light intensities This paper research on the signal modulation methods for the system: AC and DC modulations. What is more, the advantages and disadvantages of both modulations in the system will be analyzed. Considering the characteristics that the systematic noise and signal have the spectrum overlapping and that when there is any fault, the fact that in the small signal detection system the output SNR of AC modulation is better than that of DC modulation will be proved. For the parameter changes caused by the environment factors, the feedback control linked by the DSP is imported, it automatically adjusts the balance of the two branch parameters, acquires the measured component in the condition of the two branch unbalance parameters. Furthermore, this paper researches on the influence of imbalance of the dual optical path on the signal detection system. It analyzes the error characteristics due to different kinds of losses and to component matching disorders and other intrinsic factors and then put forward the method to calculate balancing factors by means of the RMS of 50Hz signal. The result proves that using this method can improve the output SNR of optical voltage/current transformer to some extent.

  7. Current neutralization and focusing of intense ion beams with a plasma-filled solenoidal lens. I

    SciTech Connect

    Oliver, B.V.; Sudan, R.N.

    1996-12-01

    The response of the magnetized plasma in an axisymmetric, plasma-filled, solenoidal magnetic lens, to intense light ion beam injection is studied. The lens plasma fill is modeled as an inertialess, resistive, electron magnetohydrodynamic (EMHD) fluid since characteristic beam times {tau} satisfy 2{pi}/{omega}{sub {ital pe}},2{pi}/{Omega}{sub {ital e}}{lt}{tau}{le}2{pi}/{Omega}{sub {ital i}} ({omega}{sub {ital pe}} is the electron plasma frequency and {Omega}{sub {ital e},{ital i}} are the electron, ion gyrofrequencies). When the electron collisionality satisfies {nu}{sub {ital e}}{lt}{Omega}{sub {ital e}}, the linear plasma response is determined by whistler wave dynamics. In this case, current neutralization of the beam is reduced on the time scale for whistler wave transit across the beam. The transit time is inversely proportional to the electron density and proportional to the angle of incidence of the beam with respect to the applied solenoidal field. In the collisional regime ({nu}{sub {ital e}}{gt}{Omega}{sub {ital e}}) the plasma return currents decay on the normal diffusive time scale determined by the conductivity. The analysis is supported by two-and-one-half dimensional hybrid particle-in-cell simulations. {copyright} {ital 1996 American Institute of Physics.}

  8. Investigation of nonthermal particle effects on ionization dynamics in high current density ion beam transport experiments

    NASA Astrophysics Data System (ADS)

    Chung, H. K.; MacFarlane, J. J.; Wang, P.; Moses, G. A.; Bailey, J. E.; Olson, C. L.; Welch, D. R.

    1997-01-01

    Light ion inertial fusion experiments require the presence of a moderate density background gas in the transport region to provide charge and current neutralization for a high current density ion beam. In this article, we investigate the effects of nonthermal particles such as beam ions or non-Maxwellian electron distributions on the ionization dynamics of the background gas. In particular, we focus on the case of Li beams being transported in an argon gas. Nonthermal particles as well as thermal electrons are included in time-dependent collisional-radiative calculations to determine time-dependent atomic level populations and charge state distributions in a beam-produced plasma. We also briefly discuss the effects of beam ions and energetic electrons on the visible and vacuum ultraviolet (VUV) spectral regions. It is found that the mean charge state of the gas, and hence the electron density, is significantly increased by collisions with energetic particles. This higher ionization significantly impacts the VUV spectral region, where numerous resonance lines occur. On the other hand, the visible spectrum tends to be less affected because the closely spaced excited states are populated by lower energy thermal electrons.

  9. Transverse match of high peak-current beam into the LANSCE DTL using PARMILA

    SciTech Connect

    Merrill, F.E.; Rybarcyk, L.J.

    1996-09-01

    A new algorithm that uses a multiparticle PARMILA-based code to match high peak current H{sup +} beam ({approx}21 mA) into the Los Alamos Neutron Science Center (LANSCE) drift tube linac (DTL) has been developed. Two single cell rf bunchers in the low energy beam transport (LEBT) prepare the initially unbunched beam for DTL capture. The transverse distribution at the entrance to the DTL is set with four quadrupoles in the 1.26 m between the last transverse emittance measuring station and the DTL entrance. Previous matching algorithms used TRACE and TRACE 3-D to determine these quadrupole strengths. PARMILA simulation show this procedure produces non-zero mismatch and additional emittance growth through the DTL for high current beams. Because of strong space-charge forces and a rapidly forming longitudinal bunch, simple envelope calculations do not model the beam evolution in the LEBT well. A PARMILA model of this region was combined with ant iterative search routine to set the LEBT quadrupole strengths to achieve a better transverse match into the DTL. Simulations predict a significant reduction in transverse emittance at the exit of the DTL over the typical TRACE 3-D result.

  10. Beam extraction and high stability operation of high current electron cyclotron resonance proton ion source

    SciTech Connect

    Roychowdhury, P. Mishra, L.; Kewlani, H.; Mittal, K. C.; Patil, D. S.

    2014-03-15

    A high current electron cyclotron resonance proton ion source is designed and developed for the low energy high intensity proton accelerator at Bhabha Atomic Research Centre. The plasma discharge in the ion source is stabilized by minimizing the reflected microwave power using four stub auto tuner and magnetic field. The optimization of extraction geometry is performed using PBGUNS code by varying the aperture, shape, accelerating gap, and the potential on the electrodes. While operating the source, it was found that the two layered microwave window (6 mm quartz plate and 2 mm boron nitride plate) was damaged (a fine hole was drilled) by the back-streaming electrons after continuous operation of the source for 3 h at beam current of 20–40 mA. The microwave window was then shifted from the line of sight of the back-streaming electrons and located after the water-cooled H-plane bend. In this configuration the stable operation of the high current ion source for several hours is achieved. The ion beam is extracted from the source by biasing plasma electrode, puller electrode, and ground electrode to +10 to +50 kV, −2 to −4 kV, and 0 kV, respectively. The total ion beam current of 30–40 mA is recorded on Faraday cup at 40 keV of beam energy at 600–1000 W of microwave power, 800–1000 G axial magnetic field and (1.2–3.9) × 10{sup −3} mbar of neutral hydrogen gas pressure in the plasma chamber. The dependence of beam current on extraction voltage, microwave power, and gas pressure is investigated in the range of operation of the ion source.

  11. Optical transition radiation used in the diagnostic of low energy and low current electron beams in particle accelerators

    SciTech Connect

    Silva, T. F.; Bonini, A. L.; Lima, R. R.; Maidana, N. L.; Malafronte, A. A.; Pascholati, P. R.; Vanin, V. R.; Martins, M. N.

    2012-09-15

    Optical transition radiation (OTR) plays an important role in beam diagnostics for high energy particle accelerators. Its linear intensity with beam current is a great advantage as compared to fluorescent screens, which are subject to saturation. Moreover, the measurement of the angular distribution of the emitted radiation enables the determination of many beam parameters in a single observation point. However, few works deals with the application of OTR to monitor low energy beams. In this work we describe the design of an OTR based beam monitor used to measure the transverse beam charge distribution of the 1.9-MeV electron beam of the linac injector of the IFUSP microtron using a standard vision machine camera. The average beam current in pulsed operation mode is of the order of tens of nano-Amps. Low energy and low beam current make OTR observation difficult. To improve sensitivity, the beam incidence angle on the target was chosen to maximize the photon flux in the camera field-of-view. Measurements that assess OTR observation (linearity with beam current, polarization, and spectrum shape) are presented, as well as a typical 1.9-MeV electron beam charge distribution obtained from OTR. Some aspects of emittance measurement using this device are also discussed.

  12. Optical transition radiation used in the diagnostic of low energy and low current electron beams in particle accelerators.

    PubMed

    Silva, T F; Bonini, A L; Lima, R R; Maidana, N L; Malafronte, A A; Pascholati, P R; Vanin, V R; Martins, M N

    2012-09-01

    Optical transition radiation (OTR) plays an important role in beam diagnostics for high energy particle accelerators. Its linear intensity with beam current is a great advantage as compared to fluorescent screens, which are subject to saturation. Moreover, the measurement of the angular distribution of the emitted radiation enables the determination of many beam parameters in a single observation point. However, few works deals with the application of OTR to monitor low energy beams. In this work we describe the design of an OTR based beam monitor used to measure the transverse beam charge distribution of the 1.9-MeV electron beam of the linac injector of the IFUSP microtron using a standard vision machine camera. The average beam current in pulsed operation mode is of the order of tens of nano-Amps. Low energy and low beam current make OTR observation difficult. To improve sensitivity, the beam incidence angle on the target was chosen to maximize the photon flux in the camera field-of-view. Measurements that assess OTR observation (linearity with beam current, polarization, and spectrum shape) are presented, as well as a typical 1.9-MeV electron beam charge distribution obtained from OTR. Some aspects of emittance measurement using this device are also discussed. PMID:23020369

  13. Beam current enhancement of microwave plasma ion source utilizing double-port rectangular cavity resonator.

    PubMed

    Lee, Yuna; Park, Yeong-Shin; Jo, Jong-Gab; Yang, J J; Hwang, Y S

    2012-02-01

    Microwave plasma ion source with rectangular cavity resonator has been examined to improve ion beam current by changing wave launcher type from single-port to double-port. The cavity resonators with double-port and single-port wave launchers are designed to get resonance effect at TE-103 mode and TE-102 mode, respectively. In order to confirm that the cavities are acting as resonator, the microwave power for breakdown is measured and compared with the E-field strength estimated from the HFSS (High Frequency Structure Simulator) simulation. Langmuir probe measurements show that double-port cavity enhances central density of plasma ion source by modifying non-uniform plasma density profile of the single-port cavity. Correspondingly, beam current from the plasma ion source utilizing the double-port resonator is measured to be higher than that utilizing single-port resonator. Moreover, the enhancement in plasma density and ion beam current utilizing the double-port resonator is more pronounced as higher microwave power applied to the plasma ion source. Therefore, the rectangular cavity resonator utilizing the double-port is expected to enhance the performance of plasma ion source in terms of ion beam extraction. PMID:22380295

  14. Beam current enhancement of microwave plasma ion source utilizing double-port rectangular cavity resonator

    SciTech Connect

    Lee, Yuna; Park, Yeong-Shin; Jo, Jong-Gab; Yang, J. J.; Hwang, Y. S.

    2012-02-15

    Microwave plasma ion source with rectangular cavity resonator has been examined to improve ion beam current by changing wave launcher type from single-port to double-port. The cavity resonators with double-port and single-port wave launchers are designed to get resonance effect at TE-103 mode and TE-102 mode, respectively. In order to confirm that the cavities are acting as resonator, the microwave power for breakdown is measured and compared with the E-field strength estimated from the HFSS (High Frequency Structure Simulator) simulation. Langmuir probe measurements show that double-port cavity enhances central density of plasma ion source by modifying non-uniform plasma density profile of the single-port cavity. Correspondingly, beam current from the plasma ion source utilizing the double-port resonator is measured to be higher than that utilizing single-port resonator. Moreover, the enhancement in plasma density and ion beam current utilizing the double-port resonator is more pronounced as higher microwave power applied to the plasma ion source. Therefore, the rectangular cavity resonator utilizing the double-port is expected to enhance the performance of plasma ion source in terms of ion beam extraction.

  15. Large-aperture continuous-phase diffractive optical element for beam transform

    NASA Astrophysics Data System (ADS)

    Tan, Qiaofeng; Yan, Yingbai; Jin, Guofan; Wu, Minxian

    1999-11-01

    Beam transform, such as to obtain uniform focal spot with flat top, steep edge, low side lobes and high light efficiency, can be realized well by diffractive optical element (DOE). The DOE has many advantages, such as high light efficiency and strong phase distribution design flexibility. To increase the light efficiency and decrease large-angle scattering, continuous phase DOE should be used. The phase design is competed by a kind of multi-resolution hybrid algorithm based on hill-climbing and simulated annealing, which exploits sufficiently strong convergence ability of the hill climbing and global optimization potential of the simulated annealing. A kind of phase distribution with good geometrical structure and diameter 80 mm is obtained by choosing disturbance function, receipt and refused probability and so on. The simulated results show that the light efficiency is more than 95 percent, and the non-uniformity is less than 5 percent. Because the etching depth is direct proportion to the exposure time, to obtain continuous phase DOE, a kind of hollowed-out mask, namely gray-scale mask is used to control exposure time of each are. The mask is manufactured by linear cutting machine. The continuous phase DOE with diameter 80mm is fabricated by ion-etching with the mask. Finally, the tolerance of manufacturing error including depth error and alignment error are analyzed.

  16. Computation of lower hybrid, neutral beam and bootstrap currents in consistent MHD equilibria

    SciTech Connect

    Devoto, R.S.; Blackfield, D.T.; Fenstermacher, M.E.; Bonoli, P.T.; Porkolab, M.

    1989-02-01

    A possible scenario for steady state current drive in large, high- temperature tokamaks includes current driven by lower hybrid (LH) waves in the outer region with high-energy neutral beams (NB) used for current drive in the core. In addition, provided the poloidal beta is sufficiently high, there can be substantial bootstrap (BS) current, as observed in the TFTR and JET experiments. In work reported previously, a computer code, ACCOME, was written to obtain a solution to the MHD equations which is consistent with current driven by neutral beams, electric fields, and neoclassical (bootstrap) effects. For the computation of the solution to the Grad-Shafranov equation, the SELENE code is used. Iteration is necessary between SELENE and the current-drive computations to obtain a consistent solution. In this paper we describe modifications to ACCOME to enable the computation of LH current in addition to the NB, BS, and OH currents. The next section describes the models used and then the final section presents an application to ITER. 4 refs., 4 figs.

  17. Proposal for direct measurement of a pure spin current by a polarized light beam.

    PubMed

    Wang, Jing; Zhu, Bang-Fen; Liu, Ren-Bao

    2008-02-29

    The photon helicity may be mapped to a spin-1/2, whereby we put forward an intrinsic interaction between a polarized light beam as a "photon spin current" and a pure spin current in a semiconductor, which arises from the spin-orbit coupling in valence bands as a pure relativity effect without involving the Rashba or the Dresselhaus effect due to inversion asymmetries. The interaction leads to linear and circular optical birefringence, which are similar to the Voigt effect and the Faraday rotation in magneto-optics but nevertheless involve no net magnetization. The birefringence effects provide a direct, nondemolition measurement of pure spin currents. PMID:18352646

  18. TRANSFORMATION

    SciTech Connect

    LACKS,S.A.

    2003-10-09

    Transformation, which alters the genetic makeup of an individual, is a concept that intrigues the human imagination. In Streptococcus pneumoniae such transformation was first demonstrated. Perhaps our fascination with genetics derived from our ancestors observing their own progeny, with its retention and assortment of parental traits, but such interest must have been accelerated after the dawn of agriculture. It was in pea plants that Gregor Mendel in the late 1800s examined inherited traits and found them to be determined by physical elements, or genes, passed from parents to progeny. In our day, the material basis of these genetic determinants was revealed to be DNA by the lowly bacteria, in particular, the pneumococcus. For this species, transformation by free DNA is a sexual process that enables cells to sport new combinations of genes and traits. Genetic transformation of the type found in S. pneumoniae occurs naturally in many species of bacteria (70), but, initially only a few other transformable species were found, namely, Haemophilus influenzae, Neisseria meningitides, Neisseria gonorrheae, and Bacillus subtilis (96). Natural transformation, which requires a set of genes evolved for the purpose, contrasts with artificial transformation, which is accomplished by shocking cells either electrically, as in electroporation, or by ionic and temperature shifts. Although such artificial treatments can introduce very small amounts of DNA into virtually any type of cell, the amounts introduced by natural transformation are a million-fold greater, and S. pneumoniae can take up as much as 10% of its cellular DNA content (40).

  19. Transformation of optical-vortex beams by holograms with embedded phase singularity

    NASA Astrophysics Data System (ADS)

    Bekshaev, A. Ya.; Orlinska, O. V.

    2010-04-01

    Spatial characteristics of diffracted beams produced by the "fork" holograms from incident circular Laguerre-Gaussian modes are studied theoretically. The complex amplitude distribution of a diffracted beam is described by models of the Kummer beam or of the hypergeometric-Gaussian beam. Physically, in most cases its structure is formed under the influence of the divergent spherical wave originating from the discontinuity caused by the hologram's groove bifurcation. Presence of this wave is manifested by the ripple structure in the near-field beam pattern and by the power-law amplitude decay at the beam periphery. Conditions when the divergent wave is not excited are discussed. The diffracted beam carries a screw wavefront dislocation (optical vortex) whose order equals to algebraic sum of the incident beam azimuthal index and the topological charge of the singularity imparted by the hologram. The input beam singularity can be healed when the above sum is zero. In such cases the diffracted beam can provide better energy concentration in the central intensity peak than the Gaussian beam whose initial distribution coincides with the Gaussian envelope of the incident beam. Applications are possible for generation of optical-vortex beams with prescribed properties and for analyzing the optical-vortex beams in problems of information processing.

  20. A high-current microwave ion source with permanent magnet and its beam emittance measurement

    SciTech Connect

    Yao Zeen; Tan Xinjian; Du Hongxin; Luo Ben; Liu Zhanwen

    2008-07-15

    The progress of a 2.45 GHz high-current microwave ion source with permanent magnet for T(d,n){sup 4}He reaction neutron generator is reported in this paper. At 600 W microwave power and 22 kV extraction voltage, 90 mA peak hydrogen ion beam is extracted from a single aperture of 6 mm diameter. The beam emittance is measured using a simplified pepper-pot method. The (x,x{sup '}) emittance and the (y,y{sup '}) emittance for 14 keV hydrogen ion beam are 55.3{pi} and 58.2{pi} mm mrad, respectively. The normalized emittances are 0.302{pi} and 0.317{pi} mm mrad, respectively.

  1. Methods for Measuring and Controlling Beam Breakup in High Current ERLS

    SciTech Connect

    Christ Tennant; Kevin Jordan; E. Pozdeyev; Robert Rimmer; Haipeng Wang; Stefen Simrock

    2004-08-01

    It is well known that high current Energy Recovery Linacs (ERL) utilizing superconducting cavities are susceptible to a regenerative type of beam breakup (BBU). The BBU instability is caused by the high impedance transverse deflecting higher-order modes (HOMs) of the cavities. This multipass, multibunch instability has been observed at Jefferson Laboratory's FEL Upgrade driver. Some preliminary measurements are presented. To combat the harmful effects of a particularly dangerous mode, two methods of directly damping HOMs through the cavity HOM couplers were demonstrated. In an effort to suppress the BBU in the presence of multiple, dangerous HOMs, a conceptual design for an injector beam-based transverse feedback system has been developed. By implementing beam-based feedback, the threshold for instability can be increased substantially.

  2. Absolute Current Calibrations of 1muA CW Electron Beam

    SciTech Connect

    A. Freyberger, M.E. Bevins, A.R. Day, P. Degtiarenko, A. Saha, S. Slachtouski, R. Gilman

    2005-06-06

    The future experimental program at Jefferson Lab requires an absolute current calibration of a 1{mu}A CW electron beam to better than 1% accuracy. This paper presents the mechanical and electrical design of a Tungsten calorimeter that is being constructed to provide an accurate measurement of the deposited energy. The energy is determined by measuring the change in temperature after beam exposure. Knowledge of the beam energy then yields number of electrons stopped by the calorimeter during the exposure. Simulations show that the energy losses due to electromagnetic and hadronic losses are the dominant uncertainty. Details of the precision thermometry and calibration, mechanical design, thermal simulations and GEANT simulations will be presented.

  3. Absolute Current Calibration of 1$\\mu$A CW Electron Beam

    SciTech Connect

    Arne Freyberger; Mike Bevins; Anthony Day; Arunava Saha; Stephanie Slachtouski; Ronald Gilman; Pavel Degtiarenko

    2005-06-01

    The future experimental program at Jefferson Lab requires an absolute current calibration of a 1 {mu}A CW electron beam to better than 1% accuracy. This paper presents the mechanical and electrical design of a Tungsten calorimeter that is being constructed to provide an accurate measurement of the deposited energy. The energy is determined by measuring the change in temperature after beam exposure. Knowledge of the beam energy then yields number of electrons stopped by the calorimeter during the exposure. Simulations show that the energy lost due to electromagnetic and hadronic particle losses are the dominant uncertainty. Details of the precision thermometry and calibration, mechanical design, thermal simulations and simulations will be presented.

  4. Curvilinear parabolic approximation for surface wave transformation with wave current interaction

    NASA Astrophysics Data System (ADS)

    Shi, Fengyan; Kirby, James T.

    2005-04-01

    The direct coordinate transformation method, which only transforms independent variables and retains Cartesian dependent variables, may not be an appropriate method for the purpose of simplifying the curvilinear parabolic approximation of the vector form of the wave-current equation given by Kirby [Higher-order approximations in the parabolic equation method for water waves, J. Geophys. Res. 91 (1986) 933-952]. In this paper, the covariant-contravariant tensor method is used for the curvilinear parabolic approximation. We use the covariant components of the wave number vector and contravariant components of the current velocity vector so that the derivation of the curvilinear equation closely follows the higher-order approximation in rectangular Cartesian coordinates in Kirby [Higher-order approximations in the parabolic equation method for water waves, J. Geophys. Res. 91 (1986) 933-952]. The resulting curvilinear equation can be easily implemented using the existing model structure and numerical schemes adopted in the Cartesian parabolic wave model [J.T. Kirby, R.A. Dalrymple, F. Shi, Combined Refraction/Diffraction Model REF/DIF 1, Version 2.6. Documentation and User's Manual, Research Report, Center for Applied Coastal Research, Department of Civil and Environmental Engineering, University of Delaware, Newark, 2004]. Several examples of wave simulations in curvilinear coordinate systems, including a case with wave-current interaction, are shown with comparisons to theoretical solutions or measurement data.

  5. Off-axis Neutral Beam Current Drive for Advanced Scenario Development in DIII-D

    SciTech Connect

    Murakami, M; Park, J; Petty, C; Luce, T; Heidbrink, W; Osborne, T; Wade, M; Austin, M; Brooks, N; Budny, R; Challis, C; DeBoo, J; deGrassie, J; Ferron, J; Gohil, P; Hobirk, J; Holcomb, C; Hollmann, E; Hong, R; Hyatt, A; Lohr, J; Lanctot, M; Makowski, M; McCune, D; Politzer, P; Prater, R; John, H S; Suzuki, T; West, W; Unterberg, E; Van Zeeland, M; Yu, J

    2008-10-13

    Modification of the two existing DIII-D neutral beam lines is proposed to allow vertical steering to provide off-axis neutral beam current drive (NBCD) as far off-axis as half the plasma radius. New calculations indicate very good current drive with good localization off-axis as long as the toroidal magnetic field, B{sub T}, and the plasma current, I{sub p}, are in the same direction (for a beam steered downward). The effects of helicity can be large: e.g., ITER off-axis NBCD can be increased by more than 20% if the B{sub T} direction is reversed. This prediction has been tested by an off-axis NBCD experiment using reduced size plasmas that are vertically shifted with the existing NBI on DIII-D. The existence of off-axis NBCD is evident in sawtooth and internal inductance behavior. By shifting the plasma upward or downward, or by changing the sign of the toroidal field, measured off-axis NBCD profiles, determined from MSE data, are consistent with predicted differences (40%-45%) arising from the NBI orientation with respect to the magnetic field lines. Modification of the DIII-D NB system will strongly support scenario development for ITER and future tokamaks as well as providing flexible scientific tools for understanding transport, energetic particles and heating and current drive.

  6. High current H- ion sources for the large helical device neutral beam injector

    NASA Astrophysics Data System (ADS)

    Oka, Y.; Tsumori, K.; Takeiri, Y.; Kaneko, O.; Osakabe, M.; Asano, E.; Kawamoto, T.; Akiyama, R.

    1998-02-01

    Two large helical device-neutral beam injector (LHD-NBI) ion sources were fabricated and tested in the test stand for producing a beam of 180 keV×40 A with H- ions. They are Cesiated multicusp ion sources with a rectangular discharge chamber and a single stage multihole accelerator. These are scaled up from the 16 A H- ion sources in the National Institute for Fusion Science (NIFS). A plasma source with a high aspect ratio was operated stably with an arc power up to ˜300 kW for 10 s, after balancing of the electron emission from the filaments was made. A satisfactorily dense and uniform plasma without mode flip was produced. Electrons accompanied by H- ions were reduced by an extraction grid with the electron trap, instead of straight holes. The electron beam component caused by the stripping of electrons from H- ions was detected with an array of calorimeters at the bottom of the connecting duct. At the first stage of the test, one of the five segment grids of the accelerator was installed. An H- ion current of 5.5 A with a current density of 27.5 mA/cm2 for 0.6 s was obtained with an arc power of 135 kW with Cs introduction. A high arc power efficiency for H- ions was observed. The intense cusp field is considered to be the important factor to improve this. The beam divergence angle at 10.4 m downstream was ˜10 mrad. Since these results satisfied our design, a full segment accelerator was tested in the next stage. Beam conditioning for five segment grids is underway. So far, an H- current of 21.0 A has been obtained at 106 keV for 0.6 s. As a result, we had good prospects for achieving the full specification of LHD-NBI ion sources, especially for achieving higher current and focused beam as well as for long pulse. The neutral beam injection experiment for the LHD is scheduled to start in the middle of 1998.

  7. NIST measurement services: Calibration service for current transformers. Special pub. (Final)

    SciTech Connect

    Ramboz, J.D.; Petersons, O.

    1991-06-01

    A calibration service at the National Institute of Standards and Technology (NIST) for laboratory-quality current transformers is described. The service provides measurements of the current ratio and the phase angle between the secondary and primary currents. In the Report of Calibration or Test, the measured ratio is reported as the product of the marked (nominal) ratio and the ratio correction factor. The measured phase angle is reported directly in milliradians (mrad) and is positive if the secondary current leads the primary. The range of primary-to-secondary current ratios that can be measured with the equipment at NIST extends from 0.25 A:5 A to 12000 A:5 A. The maximum current at the present time is about 20000 A. Estimates of calibration uncertainties, including their sources, are given and quality control procedures are described. For routine calibrations, uncertainties of + or - 0.01% for the ratio and + or - 0.1 mrad for the phase angle are quoted. However, lower uncertainties--to + or - 0.0005% or 5 parts per million (ppm) for ratio and + or - 0.005 mrad or 5 microrads for phase angle--are possible under the provisions of Special Tests.

  8. Design, fabrication, and testing of superconducting RF cavities for high average beam currents

    NASA Astrophysics Data System (ADS)

    Meidlinger, David Joseph

    For high current applications, it is desirable for the cavity shape to have a low longitudinal loss factor and to have a high beam-breakup threshold current. This dissertation describes three different cavities designed for this purpose: a six-cell elliptical cavity for particles traveling at the speed of light, a two-cell elliptical cavity for subluminal particle speeds, and a single cell cavity which uses the TM012 mode for acceleration. SUPERFISH simulations predict the peak fields in both of the elliptical cavities will not exceed the TeSLA values by more than 10% but both will have 28.7% larger apertures. The elliptical designs assume the bunch frequency equals the accelerating mode frequency. The beam pipe radius is chosen so that the cutoff frequency is less than twice that of the accelerating mode. Hence all of the monopole and dipole higher-order modes (HOMs) that can be driven by a Fourier component of the beam have low loaded Q values. This simplifies the problem of HOM damping. The TM012 cavity is predicted to have much higher peak fields than a pi-mode elliptical cavity, but offers potential advantages from its simplified shape; it is essentially a circular waveguide with curved end plates. This basic shape results in easier fabrication and simplified tuning. Two prototype two-cell cavities were fabricated and tested at cryogenic temperatures without beam.

  9. Reduction of beam current noise in the FNAL magnetron ion source

    SciTech Connect

    Bollinger, D. S. Karns, P. R. Tan, C. Y.

    2015-04-08

    The new FNAL Injector Line with a circular dimple magnetron ion source has been operational since December of 2012. Since the new injector came on line there have been variations in the H- beam current flattop observed near the downstream end of the Linac. Several different cathode geometries including a hollow cathode suggested by Dudnikov [1] were tried. Previous studies also showed that different mixtures of hydrogen and nitrogen had an effect on beam current noise [2]. We expanded on those studies by trying mixtures ranging from (0.25% nitrogen, 99.75% hydrogen) to (3% nitrogen, 97% hydrogen). The results of these studies in our test stand will be presented in this paper.

  10. Experiments on current-driven three-dimensional ion sound turbulence. I - Return-current limited electron beam injection. II - Wave dynamics

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.

    1978-01-01

    Pulsed electron beam injection into a weakly collisional magnetized background plasma is investigated experimentally; properties of the electron beam and background plasma, as well as the low-frequency instabilities and wave dynamics, are discussed. The current of the injected beam closes via a field-aligned return current of background electrons. Through study of the frequency and wavenumber distribution, together with the electron distribution function, the low-frequency instabilities associated with the pulsed injection are identified as ion acoustic waves driven unstable by the return current. The frequency cut-off of the instabilities predicted from renormalized plasma turbulence theory, has been verified experimentally.

  11. Charged current disappearance measurements in the NuMI off-axis beam

    SciTech Connect

    R. H. Bernstein

    2003-09-25

    This article studies the potential of combining charged-current disappearance measurements of {nu}{sub {mu}} {yields} {nu}{sub {tau}} from MINOS and an off-axis beam. The author finds that the error on {Delta}m{sup 2} from a 100 kt-yr off-axis measurement is a few percent of itself. Further, the author found little improvement to an off-axis measurement by combining it with MINOS.

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

    SciTech Connect

    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.

  13. Open-loop correction for an eddy current dominated beam-switching magnet

    SciTech Connect

    Koseki, K. Nakayama, H.; Tawada, M.

    2014-04-15

    A beam-switching magnet and the pulsed power supply it requires have been developed for the Japan Proton Accelerator Research Complex. To switch bunched proton beams, the dipole magnetic field must reach its maximum value within 40 ms. In addition, the field flatness should be less than 5 × 10{sup −4} to guide each bunched beam to the designed orbit. From a magnetic field measurement by using a long search coil, it was found that an eddy current in the thick endplates and laminated core disturbs the rise of the magnetic field. The eddy current also deteriorates the field flatness over the required flat-top period. The measured field flatness was 5 × 10{sup −3}. By using a double-exponential equation to approximate the measured magnetic field, a compensation pattern for the eddy current was calculated. The integrated magnetic field was measured while using the newly developed open-loop compensation system. A field flatness of less than 5 × 10{sup −4}, which is an acceptable value, was achieved.

  14. In Situ Focused Beam Reflectance Measurement (FBRM), Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and Raman Characterization of the Polymorphic Transformation of Carbamazepine

    PubMed Central

    Zhao, Yingying; Bao, Ying; Wang, Jingkang; Rohani, Sohrab

    2012-01-01

    The objective of this work was to study the polymorphic transformation of carbamazepine from Form II to Form III in 1-propanol during seeded isothermal batch crystallization. First, the pure Form II and Form III were obtained and characterized. Then their solubilities and metastable zone limits were measured by in-situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and focused beam reflectance measurement (FBRM). A transition temperature at about 34.2 °C was deduced suggesting the enantiotropic nature of this compound over the studied temperature range. To quantify the polymorph ratio during the transformation process, a new in-situ quantitative method was developed to measure the fraction of Form II by Raman spectroscopy. Successful tracking of the nucleation of the stable form and the transformation from Form II to Form III during isothermal crystallization was achieved by Raman spectroscopy and FBRM. The results from these three in-situ techniques, FBRM, FTIR and Raman were consistent with each other. The results showed a strong dependency on the amount of seeds added during isothermal crystallization. PMID:24300186

  15. Electron-beam irradiation induced transformation of Cu2(OH)3NO3 nanoflakes into nanocrystalline CuO

    NASA Astrophysics Data System (ADS)

    Padhi, S. K.; Gottapu, S. N.; Krishna, M. Ghanashyam

    2016-05-01

    The transmission electron microscope electron-beam (TEM e-beam) as a material modification tool has been demonstrated. The material modification is realised in the high-resolution TEM mode (largest condenser aperture, 150 μm, and 200 nm spot size) at a 200 keV beam energy. The Cu2(OH)3NO3 (CHN) nanoflakes used in this study were microwave solution processed that were layered single crystals and radiation sensitive. The single domain CHN flakes disintegrate into a large number of individual CuO crystallites within a 90 s span of time. The sequential bright-field, dark-field, and selected area electron diffraction modes were employed to record the evolved morphology, microstructural changes, and structural transformation that validate CHN modification. High-resolution transmission electron microscopy imaging of e-beam irradiated regions unambiguously supports the growth of CuO nanoparticles (11.8(3.2) nm in diameter). This study demonstrates e-beam irradiation induced CHN depletion, subsequent nucleation and growth of nanocrystalline CuO regions well embedded in the parent burnt porous matrix which can be useful for miniaturized sensing applications. NaBH4 induced room temperature reduction of CHN to elemental Cu and its printability on paper was also demonstrated.The transmission electron microscope electron-beam (TEM e-beam) as a material modification tool has been demonstrated. The material modification is realised in the high-resolution TEM mode (largest condenser aperture, 150 μm, and 200 nm spot size) at a 200 keV beam energy. The Cu2(OH)3NO3 (CHN) nanoflakes used in this study were microwave solution processed that were layered single crystals and radiation sensitive. The single domain CHN flakes disintegrate into a large number of individual CuO crystallites within a 90 s span of time. The sequential bright-field, dark-field, and selected area electron diffraction modes were employed to record the evolved morphology, microstructural changes, and structural

  16. A method for measuring dark current electron beams in an rf linac

    SciTech Connect

    Maruyama, X.K.; Fasanello, T.; Rietdyk, H.; Piestrup, M.A.; Rule, D.W.; Fiorito, R.B.

    1993-12-31

    X-ray fluorescence from thin foils inserted into the NPS linac has been used to measure the integrated electron beam intensity when the accelerator is operating with dark current. The measured x-ray flux, the known inner shell ionization cross sections and radiative transition probabilities are used to obtain measurements of dark currents of the order of 10{sup -14} amperes. The same arrangement allows continuous, in-situ energy calibration of our SiLi detector in the electromagnetic noise environment of the linac. This technique was orginally developed to perform absolute production efficiency measurements of parametric x-ray generation in the 5-50 keV range.

  17. High-current density, high-brightness electron beams from large-area lanthanum hexaboride cathodes

    NASA Astrophysics Data System (ADS)

    Loschialpo, P.; Kapetanakos, C. A.

    1987-12-01

    Large (approx. 5 cm) diameter lanthanum hexaboride (LaB6) cathodes operated at 10 kV have produced 1 to 5 micro electron pulses with current density between 10 and 20 A/sq cm. Normalized beam brightness, has been consistently measured. To obtain this high current density, the LaB6 cathodes have been heated to temperatures between approximately 1600 to 1800 C. Very uniform temperature profiles are obtained by applying a carefully tailored electron bombardment heating power distribution. These measurements have been made between pressure .000001 to .00001 Torr, i.e., under much less demanding vacuum conditions than that required by conventional dispenser type cathodes.

  18. Coherent Effects of High Current Beam in Project-X Linac

    SciTech Connect

    Sukhanov, A.; Lunin, A.; Yakovlev, V.; Gonin, I.; Khabiboulline, T.; Saini, A.; Solyak, N.; Yostrikov, A.

    2012-09-01

    Resonance excitation of longitudinal high order modes in superconducting RF structures of Project-X continuous wave linac is studied. We analyze regimes of operation of the linac with high beam current, which can be used to provide an intense muon source for the future Neutrino Factory or Muon Collider, and also important for the Accelerator-Driven Subcritical systems. We calculate power loss and associated heat load to the cryogenic system. Longitudinal emittance growth is estimated. We consider an alternative design of the elliptical cavity for the high energy part of the linac, which is more suitable for high current operation.

  19. Induced charging of shuttle orbiter by high electron-beam currents

    NASA Technical Reports Server (NTRS)

    Liemohn, H. B.

    1977-01-01

    Emission of high-current electron beams that was proposed for some Spacelab payloads required substantial return currents to the orbiter skin in order to neutralize the beam charge. Since the outer skin of the vehicle was covered with approximately 1200 sq m of thermal insulation which has the dielectric quality of air and an electrical conductivity that was estimated by NASA at 10 to the -9 power to 10 to the -10 power mhos/m, considerable transient charging and local potential differences were anticipated across the insulation. The theory for induced charging of spacecraft due to operation of electron guns was only developed for spherical metal vehicles and constant emission currents, which were not directly applicable to the orbiter situation. Field-aligned collection of electron return current from the ambient ionosphere at orbiter altitudes provides up to approximately 150 mA on the conducting surfaces and approximately 2.4 A on the dielectric thermal insulation. Local ionization of the neutral atmosphere by energetic electron bombardment or electrical breakdown may provide somewhat more return current.

  20. Current profile redistribution driven by neutral beam injection in a reversed-field pinch

    NASA Astrophysics Data System (ADS)

    Parke, E.; Anderson, J. K.; Brower, D. L.; Den Hartog, D. J.; Ding, W. X.; Johnson, C. A.; Lin, L.

    2016-05-01

    Neutral beam injection in reversed-field pinch (RFP) plasmas on the Madison Symmetric Torus [Dexter et al., Fusion Sci. Technol. 19, 131 (1991)] drives current redistribution with increased on-axis current density but negligible net current drive. Internal fluctuations correlated with tearing modes are observed on multiple diagnostics; the behavior of tearing mode correlated structures is consistent with flattening of the safety factor profile. The first application of a parametrized model for island flattening to temperature fluctuations in an RFP allows inferrence of rational surface locations for multiple tearing modes. The m = 1, n = 6 mode is observed to shift inward by 1.1 ± 0.6 cm with neutral beam injection. Tearing mode rational surface measurements provide a strong constraint for equilibrium reconstruction, with an estimated reduction of q0 by 5% and an increase in on-axis current density of 8% ± 5%. The inferred on-axis current drive is consistent with estimates of fast ion density using TRANSP [Goldston et al., J. Comput. Phys. 43, 61 (1981)].

  1. Amplification of current density modulation in a FEL with an infinite electron beam

    SciTech Connect

    Wang, G.; Litvinenko, V.N.; Webb, S.D.

    2011-03-28

    We show that the paraxial field equation for a free electron laser (FEL) in an infinitely wide electron beam with {kappa}-2 energy distribution can be reduced to a fourth ordinary differential equation (ODE). Its solution for arbitrary initial phase space density modulation has been derived in the wave-vector domain. For initial current modulation with Gaussian profile, close form solutions are obtained in space-time domain. In developing an analytical model for a FEL-based coherent electron cooling system, an infinite electron beam has been assumed for the modulation and correction processes. While the assumption has its limitation, it allows for an analytical close form solution to be obtained, which is essential for investigating the underlying scaling law, benchmarking the simulation codes and understanding the fundamental physics. 1D theory was previously applied to model a CeC FEL amplifier. However, the theory ignores diffraction effects and does not provide the transverse profile of the amplified electron density modulation. On the other hand, 3D theories developed for a finite electron beam usually have solutions expanded over infinite number of modes determined by the specific transverse boundary conditions. Unless the mode with the largest growth rate substantially dominates other modes, both evaluation and extracting scaling laws can be complicated. Furthermore, it is also preferable to have an analytical FEL model with assumptions consistent with the other two sections of a CeC system. Recently, we developed the FEL theory in an infinitely wide electron beam with {kappa}-1 (Lorentzian) energy distribution. Close form solutions have been obtained for the amplified current modulation initiated by an external electric field with various spatial-profiles. In this work, we extend the theory into {kappa}-2 energy distribution and study the evolution of current density induced by an initial density modulation.

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

    NASA Astrophysics Data System (ADS)

    Mazarakis, Michael G.; Fowler, William E.; Kim, Alexander A.; Sinebryukhov, Vadim A.; Rogowski, Sonrisa T.; Sharpe, Robin A.; McDaniel, Dillon H.; Olson, Craig L.; Porter, John L.; Struve, Kenneth W.; Stygar, William A.; Woodworth, Joseph R.

    2009-05-01

    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 ±100kV 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, ±100kV) will be reported in future publications.

  3. Beam current improvement and source life performance of diboron tetrafluoride (B{sub 2}F{sub 4}) for boron implantation on applied materials VIISta high current implanters

    SciTech Connect

    Tang Ying; Bassom, Neil J.; Young, James; Sweeney, Joseph; Ray, Richard

    2012-11-06

    High dose p-type boron doping is a significant productivity challenge for conventional beamline ion implant tools in semiconductor wafer fabrication. Currently, the primary feed gas for boron implantation is boron trifluoride, BF{sub 3}. This paper discusses the testing performed on Applied Materials VIISta high current implanters using diboron tetrafluoride, B{sub 2}F{sub 4}, as an alternative gaseous boron source material that can be a replacement for BF{sub 3}. Both the beam current and source life for B{sub 2}F{sub 4} were evaluated. B{sub 2}F{sub 4} enables a significant beam current improvement over BF{sub 3} while maintaining good source life, beam stability, and a high automatic beam setup success rate.

  4. Dark Currents and Their Effect on the Primary Beam in an X-band Linac

    SciTech Connect

    Bane, K.L.F.; Dolgashev, V.A.; Raubenheimer, T.; Stupakov, G.V.; Wu, J.H.; /SLAC

    2005-05-27

    We numerically study properties of primary dark currents in an X-band accelerating structure. For the H60VG3 structure considered for the Next Linear Collider (NLC) we first perform a fairly complete (with some approximations) calculation of dark current trajectories. These results are used to study properties of the dark current leaving the structure. For example, at accelerating gradient of 65 MV/m, considering two very different assumptions about dark current emission around the irises, we find that the fraction of emitted current leaving the structure to be a consistent {approx} 1%. Considering that {approx} 1 mA outgoing dark current is seen in measurement, this implies that {approx} 100 mA (or 10 pC per period) is emitted within the structure itself. Using the formalism of the Lienard-Wiechert potentials, we then perform a systematic calculation of the transverse kick of dark currents on a primary linac bunch. The result is {approx} 1 V kick per mA (or per 0.1 pC per period) dark current emitted from an iris. For an entire structure we estimate the total kick on a primary bunch to be {approx} 15 V. For the NLC linac this translates to a ratio of (final) vertical beam offset to beam size of about 0.2. However, with the assumptions that needed to be made--particularly the number of emitters and their distribution within a structure--the accuracy of this result may be limited to the order of magnitude.

  5. Development of a universal serial bus interface circuit for ion beam current integrators.

    PubMed

    Suresh, K; Panigrahi, B K; Nair, K G M

    2007-08-01

    A universal serial bus (USB) interface circuit has been developed to enable easy interfacing of commercial as well as custom-built ion beam current integrators to personal computer (PC) based automated experimental setups. Built using the popular PIC16F877A reduced instruction set computer and a USB-universal asynchronous receiver-transmitter/first in, first out controller, DLP2232, this USB interface circuit virtually emulates the ion beam current integrators on a host PC and uses USB 2.0 protocol to implement high speed bidirectional data transfer. Using this interface, many tedious and labor intensive ion beam irradiation and characterization experiments can be redesigned into PC based automated ones with advantages of improved accuracy, rapidity, and ease of use and control. This interface circuit was successfully used in carrying out online in situ resistivity measurement of 70 keV O(+) ion irradiated tin thin films using four probe method. In situ electrical resistance measurement showed the formation of SnO(2) phase during ion implantation. PMID:17764373

  6. Research of transportation efficiency of low-energy high- current electron beam in plasma channel in external magnetic field

    NASA Astrophysics Data System (ADS)

    Vagin, E. S.; Grigoriev, V. P.

    2015-11-01

    Effective high current (5-20 kA) and low energy (tens of keV) electrons beam transportation is possible only with almost complete charging neutralization. It is also necessary to use quite high current neutralization for elimination beam self-pinching effect. The research is based on the self-consistent mathematical model that takes into account beam and plasma particles dynamic, current and charge neutralization of electron beam and examines the transportation of electron beam into a chamber with low-pressure plasma in magnetic field. A numerical study was conducted using particle in cell (PIC) method. The study was performed with various system parameters: rise time and magnitude of the beam current, gas pressure and plasma density and geometry of the system. Regularities of local virtual cathode field generated by the beam in the plasma channel, as well as ranges of parameters that let transportation beam with minimal losses, depending on the external magnetic field were determined through a series of numerical studies. In addition, the assessment of the impact of the plasma ion mobility during the transition period and during steady beam was performed.

  7. Positron emission tomography imaging approaches for external beam radiation therapies: current status and future developments

    PubMed Central

    Price, P M; Green, M M

    2011-01-01

    In an era in which it is possible to deliver radiation with high precision, there is a heightened need for enhanced imaging capabilities to improve tumour localisation for diagnostic, planning and delivery purposes. This is necessary to increase the accuracy and overall efficacy of all types of external beam radiotherapy (RT), including particle therapies. Positron emission tomography (PET) has the potential to fulfil this need by imaging fundamental aspects of tumour biology. The key areas in which PET may support the RT process include improving disease diagnosis and staging; assisting tumour volume delineation; defining tumour phenotype or biological tumour volume; assessment of treatment response; and in-beam monitoring of radiation dosimetry. The role of PET and its current developmental status in these key areas are overviewed in this review, highlighting the advantages and drawbacks. PMID:21427180

  8. Investigations on CMOS photodiodes using scanning electron microscopy with electron beam induced current measurements

    NASA Astrophysics Data System (ADS)

    Kraxner, A.; Roger, F.; Loeffler, B.; Faccinelli, M.; Kirnstoetter, S.; Minixhofer, R.; Hadley, P.

    2014-09-01

    In this work the characterization of CMOS diodes with Electron Beam Induced Current (EBIC) measurements in a Scanning Electron Microscope (SEM) are presented. Three-dimensional Technology Computer Aided Design (TCAD) simulations of the EBIC measurement were performed for the first time to help interpret the experimental results. The TCAD simulations provide direct access to the spatial distribution of physical quantities (like mobility, lifetime etc.) which are very difficult to obtain experimentally. For the calibration of the simulation to the experiments, special designs of vertical p-n diodes were fabricated. These structures were investigated with respect to doping concentration, beam energy, and biasing. A strong influence of the surface preparation on the measurements and the extracted diffusion lengths are shown.

  9. Electron-beam irradiation induced transformation of Cu2(OH)3NO3 nanoflakes into nanocrystalline CuO.

    PubMed

    Padhi, S K; Gottapu, S N; Krishna, M Ghanashyam

    2016-06-01

    The transmission electron microscope electron-beam (TEM e-beam) as a material modification tool has been demonstrated. The material modification is realised in the high-resolution TEM mode (largest condenser aperture, 150 μm, and 200 nm spot size) at a 200 keV beam energy. The Cu2(OH)3NO3 (CHN) nanoflakes used in this study were microwave solution processed that were layered single crystals and radiation sensitive. The single domain CHN flakes disintegrate into a large number of individual CuO crystallites within a 90 s span of time. The sequential bright-field, dark-field, and selected area electron diffraction modes were employed to record the evolved morphology, microstructural changes, and structural transformation that validate CHN modification. High-resolution transmission electron microscopy imaging of e-beam irradiated regions unambiguously supports the growth of CuO nanoparticles (11.8(3.2) nm in diameter). This study demonstrates e-beam irradiation induced CHN depletion, subsequent nucleation and growth of nanocrystalline CuO regions well embedded in the parent burnt porous matrix which can be useful for miniaturized sensing applications. NaBH4 induced room temperature reduction of CHN to elemental Cu and its printability on paper was also demonstrated. PMID:27181995

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

    SciTech Connect

    Ward, Kevin S.; Long, Finis W.; Sinebryukhov, Vadim A. , Tomsk, Russia); Kim, Alexandre A. , Tomsk, RUSSIA); Wakeland, Peter Eric; McKee, G. Randall; Woodworth, Joseph Ray; McDaniel, Dillon Heirman; Fowler, William E.; Mazarakis, Michael Gerrassimos; Porter, John Larry, Jr.; Struve, Kenneth William; Stygar, William A.; LeChien, Keith R.; Matzen, Maurice Keith

    2010-04-01

    Sandia National Laboratories, Albuquerque, N.M., USA, in collaboration with the High Current Electronic Institute (HCEI), Tomsk, Russia, is developing a new paradigm in pulsed power technology: the Linear Transformer Driver (LTD) technology. This technological approach can provide very compact devices that can deliver very fast high current and high voltage pulses straight out of the cavity with out any complicated pulse forming and pulse compression network. Through multistage inductively insulated voltage adders, the output pulse, increased in voltage amplitude, can be applied directly to the load. The load may be a vacuum electron diode, a z-pinch wire array, a gas puff, a liner, an isentropic compression load (ICE) to study material behavior under very high magnetic fields, or a fusion energy (IFE) target. This is because the output pulse rise time and width can be easily tailored to the specific application needs. In this paper we briefly summarize the developmental work done in Sandia and HCEI during the last few years, and describe our new MYKONOS Sandia High Current LTD Laboratory.

  11. Determination of the ReA Electron Beam Ion Trap electron beam radius and current density with an X-ray pinhole camera.

    PubMed

    Baumann, Thomas M; Lapierre, Alain; Kittimanapun, Kritsada; Schwarz, Stefan; Leitner, Daniela; Bollen, Georg

    2014-07-01

    The Electron Beam Ion Trap (EBIT) of the National Superconducting Cyclotron Laboratory at Michigan State University is used as a charge booster and injector for the currently commissioned rare isotope re-accelerator facility ReA. This EBIT charge breeder is equipped with a unique superconducting magnet configuration, a combination of a solenoid and a pair of Helmholtz coils, allowing for a direct observation of the ion cloud while maintaining the advantages of a long ion trapping region. The current density of its electron beam is a key factor for efficient capture and fast charge breeding of continuously injected, short-lived isotope beams. It depends on the radius of the magnetically compressed electron beam. This radius is measured by imaging the highly charged ion cloud trapped within the electron beam with a pinhole camera, which is sensitive to X-rays emitted by the ions with photon energies between 2 keV and 10 keV. The 80%-radius of a cylindrical 800 mA electron beam with an energy of 15 keV is determined to be r(80%) = (212 ± 19)μm in a 4 T magnetic field. From this, a current density of j = (454 ± 83)A/cm(2) is derived. These results are in good agreement with electron beam trajectory simulations performed with TriComp and serve as a test for future electron gun design developments. PMID:25085129

  12. Determination of the ReA Electron Beam Ion Trap electron beam radius and current density with an X-ray pinhole camera

    SciTech Connect

    Baumann, Thomas M. Lapierre, Alain Kittimanapun, Kritsada; Schwarz, Stefan; Leitner, Daniela; Bollen, Georg

    2014-07-15

    The Electron Beam Ion Trap (EBIT) of the National Superconducting Cyclotron Laboratory at Michigan State University is used as a charge booster and injector for the currently commissioned rare isotope re-accelerator facility ReA. This EBIT charge breeder is equipped with a unique superconducting magnet configuration, a combination of a solenoid and a pair of Helmholtz coils, allowing for a direct observation of the ion cloud while maintaining the advantages of a long ion trapping region. The current density of its electron beam is a key factor for efficient capture and fast charge breeding of continuously injected, short-lived isotope beams. It depends on the radius of the magnetically compressed electron beam. This radius is measured by imaging the highly charged ion cloud trapped within the electron beam with a pinhole camera, which is sensitive to X-rays emitted by the ions with photon energies between 2 keV and 10 keV. The 80%-radius of a cylindrical 800 mA electron beam with an energy of 15 keV is determined to be r{sub 80%}=(212±19)μm in a 4 T magnetic field. From this, a current density of j = (454 ± 83)A/cm{sup 2} is derived. These results are in good agreement with electron beam trajectory simulations performed with TriComp and serve as a test for future electron gun design developments.

  13. Determination of the ReA Electron Beam Ion Trap electron beam radius and current density with an X-ray pinhole camera

    NASA Astrophysics Data System (ADS)

    Baumann, Thomas M.; Lapierre, Alain; Kittimanapun, Kritsada; Schwarz, Stefan; Leitner, Daniela; Bollen, Georg

    2014-07-01

    The Electron Beam Ion Trap (EBIT) of the National Superconducting Cyclotron Laboratory at Michigan State University is used as a charge booster and injector for the currently commissioned rare isotope re-accelerator facility ReA. This EBIT charge breeder is equipped with a unique superconducting magnet configuration, a combination of a solenoid and a pair of Helmholtz coils, allowing for a direct observation of the ion cloud while maintaining the advantages of a long ion trapping region. The current density of its electron beam is a key factor for efficient capture and fast charge breeding of continuously injected, short-lived isotope beams. It depends on the radius of the magnetically compressed electron beam. This radius is measured by imaging the highly charged ion cloud trapped within the electron beam with a pinhole camera, which is sensitive to X-rays emitted by the ions with photon energies between 2 keV and 10 keV. The 80%-radius of a cylindrical 800 mA electron beam with an energy of 15 keV is determined to be r_{80%}=(212± 19)μm in a 4 T magnetic field. From this, a current density of j = (454 ± 83)A/cm2 is derived. These results are in good agreement with electron beam trajectory simulations performed with TriComp and serve as a test for future electron gun design developments.

  14. Optimal conditions for high current proton irradiations at the university of Wisconsin's ion beam laboratory

    SciTech Connect

    Wetteland, C. J.; Field, K. G.; Gerczak, T. J.; Eiden, T. J.; Maier, B. R.; Albakri, O.; Sridharan, K.; Allen, T. R.

    2013-04-19

    The National Electrostatics Corporation's (NEC) Toroidal Volume Ion Source (TORVIS) source is known for exceptionally high proton currents with minimal service downtime as compared to traditional sputter sources. It has been possible to obtain over 150{mu}A of proton current from the source, with over 70{mu}A on the target stage. However, beam fluxes above {approx}1 Multiplication-Sign 10{sup 17}/m2-s may have many undesirable effects, especially for insulators. This may include high temperature gradients at the surface, sputtering, surface discharge, cracking or even disintegration of the sample. A series of experiments were conducted to examine the role of high current fluxes in a suite of ceramics and insulating materials. Results will show the optimal proton irradiation conditions and target mounting strategies needed to minimize unwanted macro-scale damage, while developing a procedure for conducting preliminary radiation experiments.

  15. Beam Effects from an Increase of LINAC Current from 40 ma to 49 Milliamperes

    SciTech Connect

    Ray Tomlin

    2002-06-05

    On March 25, 2002 the FNAL Linac had been running at a decreased 40 ma of beam current for some time. Both the 400 MeV Linac and the 8GeV Booster had been tuned to optimum running during that time. Optimum running for the Booster was at 4.1e12 per pulse. Losses at injection and at transition were limiting intensity at the time. By March 26, 2002 the Linac beam current had been increased to 49 ma. The optimum Booster intensity immediately jumped to 4.5e12 per pulse and increased in the next few days to 4.8e12 and 5e12 per pulse. Booster was not retuned until early April when a low-loss 5.0e12 was obtained for stacking operations. Linac current had sagged to 47 ma by then. Measurements were made on the 25th at 40 ma and the 26th and 27th at 49 ma. This is a report and discussion of those measurements.

  16. Electron beam induced current profiling of the p-ZnO:N/n-GaN heterojunction

    SciTech Connect

    Przeździecka, E. Stachowicz, M.; Chusnutdinow, S.; Jakieła, R.; Kozanecki, A.

    2015-02-09

    The high quality p-n structures studied consist of nitrogen doped ZnO:N films grown by plasma assisted molecular beam epitaxy on n-type GaN templates. The nitrogen concentration, determined by secondary ion mass spectroscopy, is about 1 × 10{sup 20} cm{sup −3}. Temperature dependent photoluminescence studies confirm the presence of acceptor centers with an energy level lying approximately 130 meV above the valence band. The maximum forward-to-reverse current ratio I{sub F}/I{sub R} in the obtained p-n diodes is about 10{sup 7} at ±5 V, which is 2–5 orders of magnitude higher than previously reported for this type of heterojunctions. Electron-beam-induced current measurements confirm the presence of a p–n junction, located at the p-ZnO/n-GaN interface. The calculated diffusion length and activation energy of minority carriers are presented. The heterostructures exhibit strong absorption in the UV range with a four orders of magnitude high bright-to-dark current ratio.

  17. Flow Transformation in Pyroclastic Density Currents: Entrainment and Granular Dynamics during the 2006 eruption of Tungurahua

    NASA Astrophysics Data System (ADS)

    Dufek, J.; Benage, M. C.; Geist, D.; Harpp, K. S.

    2013-12-01

    Pyroclastic density currents are ground hugging flows composed of hot gases, fragments of juvenile magmatic material, and entrained clasts from the conduit or the edifice over which the flows have traveled. The interior of these flows are opaque to observation due to their large ash content, but recent investigations have highlighted that there are likely strong gradients in particle concentration and segregation of particle sizes in these particle-laden gravity currents. Pyroclastic density currents refer to a broad range of phenomena from dense flows in which the dynamics are dominated by frictional interaction between particles (dense granular flows), to gas fluidized flows, to dilute flows dominated by particle-gas turbulent interaction. However, abrupt flow transformation (e.g. from dense to dilute pyroclastic density currents) can arise due to energy exchange across multiple length scales and phases, and understanding these flow transformations is important in delineating the entrainment and erosion history of these flows, interpretations of their deposits, and in better understanding the hazards they present. During the 2006 eruption of Tungurahua, Ecuador numerous, dense pyroclastic density currents descended the volcano as result of boiling-over or low column collapse eruptions. The deposits of these flows typically have pronounced snouts and levees, and are often dominated by large, clasts (meter scale in some locations). There is an exceptional observational record of these flows and their deposits, permitting detailed field constraints of their dynamics. A particularly interesting set of flows occurred on Aug. 17, 2006 during the paroxysmal phase of the eruption that descended the slope of the volcano, filled in the river channel of the Chambo river, removing much of the larger clasts from the flow, and resulting in a dilute ';surge' that transported finer material across the channel and uphill forming dune features on the opposite bank of the river. We

  18. On the theory of electron-beam-induced current contrast from pointlike defects in semiconductors

    NASA Astrophysics Data System (ADS)

    Jakubowicz, A.

    1985-02-01

    An approximate solution of the problem of the electron-beam-induced current contrast from point-like defects in a semi-infinite semiconductor is given, which differs from that of Donolato [Optik (Stuttgart) 52, 19 (1978/79)]. The ``strength of the defect'' is characterized by an effective radius. The contrast is shown to be a nonlinear function of the strength of the defect. The results are in qualitative agreement with new experimental data of Ourmazd, Wilshaw, and Booker [in Proceedings of the 41st Annual Meeting of the Electron Microscopy Society of America, edited by G. W. Bailey (San Francisco Press, San Fransisco, 1983), p. 142].

  19. Near field to far field transformations and multiple beam forming and steering

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The feasibility of acoustic verification of microwave near field to far field transformation algorithms using the Phased Array Sonic Simulation System was studied. Existing electromagnetic near field measurement techniques and transformation algorithms (equations) were investigated. It was analytically determined that acoustic verification is valid. Acoustic simulation of electromagnetic near field to far field transformations is emphasized. The acoustic simulation of electromagnetic near field to far field transformation is verified for the modal expansion method. In the modal expansion method, data from antenna near field measurements are converted to a summation or spectrum of modes corresponding to wave numbers in the measurement coordinate system. Fourier transformation of those measurements preserves the far field information in a spectral form that is then readily extractable.

  20. An optical system to transform the output beam of a quantum cascade laser to be uniform

    NASA Astrophysics Data System (ADS)

    Jacobson, Jordan M.

    Quantum cascade lasers (QCLs) are a candidate for calibration sources in space-based remote sensing applications. However, the output beam from a QCL has some characteris- tics that are undesirable in a calibration source. The output beam from a QCL is polarized, both temporally and spatially coherent, and has a non-uniform bivariate Gaussian prole. These characteristics need to be mitigated before QCLs can be used as calibration sources. This study presents the design and implementation of an optical system that manipulates the output beam from a QCL so that it is spatially and angularly uniform with reduced coherence and polarization. (85 pages).

  1. Characterization of beam-driven instabilities and current redistribution in MST plasmas

    NASA Astrophysics Data System (ADS)

    Parke, E.

    2015-11-01

    A unique, high-rep-rate (>10 kHz) Thomson scattering diagnostic and a high-bandwidth FIR interferometer-polarimeter on MST have enabled characterization of beam-driven instabilities and magnetic equilibrium changes observed during high power (1 MW) neutral beam injection (NBI). While NBI leads to negligible net current drive, an increase in on-axis current density observed through Faraday rotation is offset by a reduction in mid-radius current. Identification of the phase flip in temperature fluctuations associated with tearing modes provides a sensitive measure of rational surface locations. This technique strongly constrains the safety factor for equilibrium reconstruction and provides a powerful new tool for measuring the equilibrium magnetic field. For example, the n = 6 temperature structure is observed to shift inward 1.1 +/- 0.6 cm, with an estimated reduction of q0 by 5%. This is consistent with a mid-radius reduction in current, and together the Faraday rotation and Thomson scattering measurements corroborate an inductive redistribution of current that compares well with TRANSP/MSTFit predictions. Interpreting tearing mode temperature structures in the RFP remains challenging; the effects of multiple, closely-spaced tearing modes on the mode phase measurement require further verification. In addition to equilibrium changes, previous work has shown that the large fast ion population drives instabilities at higher frequencies near the Alfvén continuum. Recent observations reveal a new instability at much lower frequency (~7 kHz) with strongly chirping behavior. It participates in extensive avalanches of the higher frequency energetic particle and Alfvénic modes to drive enhanced fast ion transport. Internal structures measured from Te and ne fluctuations, their dependence on the safety factor, as well as frequency scaling motivate speculation about mode identity. Work supported by U.S. DOE.

  2. An investigation of electrical current induced phase transformations in the NiPtSi/polysilicon system

    NASA Astrophysics Data System (ADS)

    Kim, Deok-kee; Domenicucci, Anthony; Iyer, Subramanian S.

    2008-04-01

    We studied phase transformations and microstructural changes of NiPtSi/polysilicon fuses programmed with three different current densities (under, optimal, and over programming). Electromigration of NiPt toward the anode occurred in all three cases studied. Achieving high resistance after the fuse programming strongly depends on the kinetics of the electromigration and dopant diffusion processes which operate during the fuse blow. A thick silicide region was formed after electrically programmable fuse programming by the reaction of the electromigrated NiPt with the polysilicon layer underneath. The low tails of the underprogrammed fuses seemed to result from the incomplete electromigration and the incomplete dopant depletion due to the insufficient programming current density, while the depletion of the implanted dopants due to the sufficiently elevated temperature seemed to make the postresistance of the optimally programmed fuse higher. In the overprogrammed fuse, the newly formed silicide seemed to have further electromigrated due to the sufficiently high temperature during programming, which caused voids and hillocks. The high temperature caused melting of the polysilicon and the surrounding nitride layer, and their reaction as well. The conduction paths created by the unremoved silicide in fuse link caused the postprogramming resistance of the overprogrammed fuse to be low.

  3. High-resolution velocimetry in energetic tidal currents using a convergent-beam acoustic Doppler profiler

    SciTech Connect

    Sellar, Brian; Harding, Samuel F.; Richmond, Marshall C.

    2015-07-16

    An array of convergent acoustic Doppler velocimeters has been developed and tested for the high resolution measurement of three-dimensional tidal flow velocities in an energetic tidal site. This configuration has been developed to increase spatial resolution of velocity measurements in comparison to conventional acoustic Doppler profilers (ADPs) which characteristically use diverging acoustic beams emanating from a single instrument. This is achieved using converging acoustic beams with a sample volume at the focal point of 0.03 m3. The array is also able to simultaneously measure three-dimensional velocity components in a profile throughout the water column, and as such is referred to herein as a converging-beam acoustic Doppler profiler (CADP). Mid-depth profiling is achieved through integration of the sensor platform with the operational Alstom 1MW DeepGen-IV Tidal Turbine. This proof-of-concept paper outlines system configuration and comparison to measurements provided by co-installed reference instrumentation. Comparison of CADP to standard ADP velocity measurements reveals a mean difference of 8 mm/s, standard deviation of 18 mm/s, and order-of-magnitude reduction in realizable length-scale. CADP focal point measurements compared to a proximal single-beam reference show peak cross-correlation coefficient of 0.96 over 4.0 s averaging period and a 47% reduction in Doppler noise. The dual functionality of the CADP as a profiling instrument with a high resolution focal point make this configuration a unique and valuable advancement in underwater velocimetry enabling improved turbulence, resource and structural loading quantification and validation of numerical simulations. Alternative modes of operation have been implemented including noise-reducing bi-static sampling. Since waves are simultaneously measured it is expected that derivatives of this system will be a powerful tool in wave-current interaction studies.

  4. Two-pion exchange electromagnetic current in chiral effective field theory using the method of unitary transformation

    SciTech Connect

    Koelling, S.; Epelbaum, E.; Krebs, H.; Meissner, U.-G.

    2009-10-15

    We derive the leading two-pion-exchange contributions to the two-nucleon electromagnetic current operator in the framework of chiral effective field theory using the method of unitary transformation. Explicit results for the current and charge densities are given in momentum and coordinate space.

  5. Transformation of phase dislocations under acousto-optic interaction of optical and acoustical Bessel beams

    NASA Astrophysics Data System (ADS)

    Belyi, V. N.; Khilo, P. A.; Kazak, N. S.; Khilo, N. A.

    2016-07-01

    The generation of wavefront phase dislocations of vortex Bessel light beams under acousto-optic (AO) diffraction in uniaxial crystals has been investigated. For the first time the process of AO interaction is studied with participation of Bessel acoustic beams instead of plane waves. A mathematical description of AO interaction is provided, which supposes the satisfaction of two types of phase-matching condition. The acousto-optic processes of transferring optical singularities onto the wavefront of BLBs are investigated and the generation of high-order optical vortices is considered at the interaction of optical and acoustical Bessel beams. The change of Bessel function order or phase dislocation order is explained as a result of the spin–orbital interaction under acousto-optic diffraction of vortex Bessel beams.

  6. Experimental geometry for simultaneous beam characterization and sample imaging allowing for pink beam Fourier transform holography or coherent diffractive imaging

    SciTech Connect

    Flewett, Samuel; Eisebitt, Stefan

    2011-02-20

    One consequence of the self-amplified stimulated emission process used to generate x rays in free electron lasers (FELs) is the intrinsic shot-to-shot variance in the wavelength and temporal coherence. In order to optimize the results from diffractive imaging experiments at FEL sources, it will be advantageous to acquire a means of collecting coherence and spectral information simultaneously with the diffraction pattern from the sample we wish to study. We present a holographic mask geometry, including a grating structure, which can be used to extract both temporal and spatial coherence information alongside the sample scatter from each individual FEL shot and also allows for the real space reconstruction of the sample using either Fourier transform holography or iterative phase retrieval.

  7. On the Beam Induced Quasi-instability Transformation of the Damped Aperiodic Mode in the Intergalactic Medium

    NASA Astrophysics Data System (ADS)

    Kolberg, U.; Schlickeiser, R.; Yoon, P. H.

    2016-02-01

    Highly relativistic electron-positron pair beams considerably affect the spontaneously emitted field fluctuations in the unmagnetized intergalactic medium (IGM). In view of the considered small density ratio of beam and background plasma, a perturbative treatment is employed in order to derive the spectral balance equations for the fluctuating fields from first principles of plasma kinetic theory that are covariantly correct within the limits of special relativity. They self-consistently account for the competing effects of spontaneous and induced emission and absorption in the perturbed thermal plasma. It is found that the presence of the beam transforms the growth rate of the dominating transverse damped aperiodic mode into an effective growth rate that displays positive values in certain spectral regions if beam velocity and wave vector are perpendicular or almost perpendicular to each other. This corresponds to a quasi-instability that induces an amplification of the fluctuations for these wavenumbers. Such an effect can greatly influence the cosmic magnetogenesis as it affects the strengths of the spontaneously emitted magnetic seed fields in the IGM, thereby possibly lowering the required growth time and effectivity of any further amplification mechanism such as an astrophysical dynamo.

  8. Solar cell evaluation using electron beam induced current with the large chamber scanning electron microscope

    NASA Astrophysics Data System (ADS)

    Wink, Tara; Kintzel, Edward; Marienhoff, Peter; Klein, Martin

    2012-02-01

    An initial study using electron beam induced current (EBIC) to evaluate solar cells has been carried out with the large chamber scanning electron microscope (LC-SEM) at the Western Kentucky University Nondestructive Analysis Center. EBIC is a scanning electron microscope technique used for the characterization of semiconductors. To facilitate our studies, we developed a Solar Amplification System (SASY) for analyzing current distribution and defects within a solar cell module. Preliminary qualitative results will be shown for a solar cell module that demonstrates the viability of the technique using the LC-SEM. Quantitative EBIC experiments will be carried out to analyze defects and minority carrier properties. Additionally, a well-focused spot of light from an LED mounted at the side of the SEM column will scan the same area of the solar cell using the LC-SEM positioning system. SASY will then output the solar efficiency to be compared with the minority carrier properties found using EBIC.

  9. 10 orders of magnitude current measurement digitisers for the CERN beam loss systems

    NASA Astrophysics Data System (ADS)

    Viganò, W.; Alsdorf, M.; Dehning, B.; Kwiatkowski, M.; Venturini, G. G.; Zamantzas, C.

    2014-02-01

    A wide range current digitizer card is needed for the acquisition module of the beam loss monitoring systems in the CERN Injector Complex. The fully differential frequency converter allows measuring positive and negative input currents with a resolution of 31 nA in an integration window of 2 μs. Increasing the integration window, the dynamic range covers 21010 were the upper part of the range is converted by measuring directly the voltage drop on a resistor. The key elements of this design are the fully differential integrator and the switches operated by an FPGA. The circuit is designed to avoid any dead time in the acquisition and reliability and failsafe operational considerations are main design goals. The circuit will be discussed in detail and lab and field measurements will be shown.

  10. Investigation of degradation mechanisms of perovskite-based photovoltaic devices using laser beam induced current mapping

    NASA Astrophysics Data System (ADS)

    Song, Zhaoning; Watthage, Suneth C.; Phillips, Adam B.; Liyanage, Geethika K.; Khanal, Rajendra R.; Tompkins, Brandon L.; Ellingson, Randy J.; Heben, Michael J.

    2015-09-01

    Solution processed thin film photovoltaic devices incorporating organohalide perovskites have progressed rapidly in recent years and achieved energy conversion efficiencies greater than 20%. However, an important issue limiting their commercialization is that device efficiencies often drop within the first few hundred hours of operation. To explore the origin of the device degradation and failure in perovskite solar cells, we investigated the spatial uniformity of current collection at different stages of aging using two-dimensional laser beam induced current (LBIC) mapping. We validated that the local decomposition of the perovskite material is likely due to interactions with moisture in the air by comparing photocurrent collection in perovskite devices that were maintained in different controlled environments. We show that the addition of a poly(methyl methacrylate)/single-wall carbon nanotube (PMMA/SWCNT) encapsulation layer prevents degradation of the device in moist air. This suggests a route toward perovskite solar cells with improved operational stability and moisture resistance.

  11. High-current density, high-brightness electron beams from large-area lanthanum hexaboride cathodes

    NASA Astrophysics Data System (ADS)

    Loschialpo, P.; Kapetanakos, C. A.

    1988-04-01

    Large diameter lanthanum hexaboride (LaB6) cathodes operated at 10 kV have produced 1-5-microsec electron pulses with current density between 10 and 20 A/sq cm. Normalized beam brightness, approximately 300,000 A/sq cm sq rad has been consistently measured. To obtain this high-current density, the LaB6 cathodes have been heated to temperatures between about 1600 and 1800 C. Very uniform temperature profiles are obtained by applying a carefully tailored electron bombardment heating power distribution. These measurements have been made between pressure 10 to the -6th to -10 to the -5th Torr, i.e., under much less demanding vacuum conditions than that required by conventional dispenser-type cathodes.

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

    SciTech Connect

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

    2012-02-15

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

  13. Measurement of inclusive charged current interactions on carbon in a few-GeV neutrino beam

    SciTech Connect

    Nakajima, Y.; jima, Y.Naka; Alcaraz-Aunion, J.L.; Brice, S.J.; Bugel, L.; Catala-Perez, J.; Cheng, G.; Conrad, J.M.; Djurcic, Z.; Dore, U.; Finley, D.A.; /Kyoto U. /Barcelona, IFAE /Fermilab /MIT /Valencia U. /Columbia U. /MIT /Columbia U. /INFN, Rome /Rome U. /Fermilab /Columbia U. /INFN, Rome /Rome U.

    2010-11-01

    The SciBooNE Collaboration reports a measurement of inclusive charged current interactions of muon neutrinos on carbon with an average energy of 0.8 GeV using the Fermilab Booster Neutrino Beam. We compare our measurement with two neutrino interaction simulations: NEUT and NUANCE. The charged current interaction rates (product of flux and cross section) are extracted by fitting the muon kinematics, with a precision of 6-15% for the energy dependent and 3% for the energy integrated analyses. We also extract CC inclusive interaction cross sections from the observed rates, with a precision of 10-30% for the energy dependent and 8% for the energy integrated analyses. This is the first measurement of the CC inclusive cross section on carbon around 1 GeV. These results can be used to convert previous SciBooNE cross section ratio measurements to absolute cross section values.

  14. Structural transitions in electron beam deposited Co-carbonyl suspended nanowires at high electrical current densities.

    PubMed

    Gazzadi, Gian Carlo; Frabboni, Stefano

    2015-01-01

    Suspended nanowires (SNWs) have been deposited from Co-carbonyl precursor (Co2(CO)8) by focused electron beam induced deposition (FEBID). The SNWs dimensions are about 30-50 nm in diameter and 600-850 nm in length. The as-deposited material has a nanogranular structure of mixed face-centered cubic (FCC) and hexagonal close-packed (HCP) Co phases, and a composition of 80 atom % Co, 15 atom % O and 5 atom % C, as revealed by transmission electron microscopy (TEM) analysis and by energy-dispersive X-ray (EDX) spectroscopy, respectively. Current (I)-voltage (V) measurements with current densities up to 10(7) A/cm(2) determine different structural transitions in the SNWs, depending on the I-V history. A single measurement with a sudden current burst leads to a polycrystalline FCC Co structure extended over the whole wire. Repeated measurements at increasing currents produce wires with a split structure: one half is polycrystalline FCC Co and the other half is graphitized C. The breakdown current density is found at 2.1 × 10(7) A/cm(2). The role played by resistive heating and electromigration in these transitions is discussed. PMID:26199833

  15. Neutral-beam current-driven high-poloidal-beta operation of the DIII-D tokamak

    SciTech Connect

    Simonen, T.C.; Matsuoka, M.; Bhadra, D.K.; Burrell, K.H.; Callis, R.W.; Chance, M.S.; Chu, M.S.; Greene, J.M.; Groebner, R.J.; Harvey, R.W.; and others

    1988-10-10

    Neutral-beam current-drive experiments in the DIII-D tokamak with a single null poloidal divertor are described. A plasma current of 0.34 MA has been sustained by neutral beams alone, and the energy confinement is of H-mode quality. Poloidal ..beta.. values reach 3.5 without disruption or coherent magnetic activity suggesting that these plasmas may be entering the second stability regime.

  16. Obtaining a proton beam with 5-mA current in a tandem accelerator with vacuum insulation

    NASA Astrophysics Data System (ADS)

    Ivanov, A. A.; Kasatov, D. A.; Koshkarev, A. M.; Makarov, A. N.; Ostreinov, Yu. M.; Sorokin, I. N.; Taskaev, S. Yu.; Shchudlo, I. M.

    2016-06-01

    Suppression of parasitic electron flows and positive ions formed in the beam tract of a tandem accelerator with vacuum insulation allowed a more than threefold increase (from 1.6 to 5 mA) in the current of accelerated 2-MeV protons. Details of the modification are described. Results of experimental investigation of the suppression of secondary charged particles and data on the characteristics of accelerated proton beam with increased current are presented.

  17. Progress and future developments of high current ion source for neutral beam injector in the ASIPP

    SciTech Connect

    Hu, Chundong; Xie, Yahong Xie, Yuanlai; Liu, Sheng; Liu, Zhimin; Xu, Yongjian; Liang, Lizhen; Sheng, Peng; Jiang, Caichao

    2015-04-08

    A high current hot cathode bucket ion source, which based on the US long pulse ion source is developed in Institute of Plasma Physics, Chinese Academy of Sciences. The ion source consists of a bucket plasma generator with multi-pole cusp fields and a set of tetrode accelerator with slit apertures. So far, four ion sources are developed and conditioned on the ion source test bed. 4 MW hydrogen beam with beam energy of 80 keV is extracted. In Aug. 2013, EAST NBI 1 with two ion source installed on the EAST, and achieved H-mode plasma with NBI injection for the first time. In order to achieve stable long pulse operation of high current ion source and negative ion source research, the RF ion source with 200 mm diameter and 120 mm depth driver is designed and developed. The first RF plasma generated with 2 kW power of 1 MHz frequency. More of the RF plasma tests and negative source relative research need to do in the future.

  18. Finite-element 3D simulation tools for high-current relativistic electron beams

    NASA Astrophysics Data System (ADS)

    Humphries, Stanley; Ekdahl, Carl

    2002-08-01

    The DARHT second-axis injector is a challenge for computer simulations. Electrons are subject to strong beam-generated forces. The fields are fully three-dimensional and accurate calculations at surfaces are critical. We describe methods applied in OmniTrak, a 3D finite-element code suite that can address DARHT and the full range of charged-particle devices. The system handles mesh generation, electrostatics, magnetostatics and self-consistent particle orbits. The MetaMesh program generates meshes of conformal hexahedrons to fit any user geometry. The code has the unique ability to create structured conformal meshes with cubic logic. Organized meshes offer advantages in speed and memory utilization in the orbit and field solutions. OmniTrak is a versatile charged-particle code that handles 3D electric and magnetic field solutions on independent meshes. The program can update both 3D field solutions from the calculated beam space-charge and current-density. We shall describe numerical methods for orbit tracking on a hexahedron mesh. Topics include: 1) identification of elements along the particle trajectory, 2) fast searches and adaptive field calculations, 3) interpolation methods to terminate orbits on material surfaces, 4) automatic particle generation on multiple emission surfaces to model space-charge-limited emission and field emission, 5) flexible Child law algorithms, 6) implementation of the dual potential model for 3D magnetostatics, and 7) assignment of charge and current from model particle orbits for self-consistent fields.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    A high current density (≈3 mA/cm2) hydrogen ion beam source operating in an extremely low-energy region (Eib ≈ 150-200 eV) has been realized by using a transition to a highly focused state, where the beam is extracted from the ion source chamber through three concave electrodes with nominal focal lengths of ≈350 mm. The transition occurs when the beam energy exceeds a threshold value between 145 and 170 eV. Low-level hysteresis is observed in the transition when Eib is being reduced. The radial profiles of the ion beam current density and the low temperature ion current density can be obtained separately using a Faraday cup with a grid in front. The measured profiles confirm that more than a half of the extracted beam ions reaches the target plate with a good focusing profile with a full width at half maximum of ≈3 cm. Estimation of the particle balances in beam ions, the slow ions, and the electrons indicates the possibility that the secondary electron emission from the target plate and electron impact ionization of hydrogen may play roles as particle sources in this extremely low-energy beam after the compensation of beam ion space charge.

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

    PubMed

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

    2015-11-01

    A high current density (≈3 mA/cm(2)) hydrogen ion beam source operating in an extremely low-energy region (E(ib) ≈ 150-200 eV) has been realized by using a transition to a highly focused state, where the beam is extracted from the ion source chamber through three concave electrodes with nominal focal lengths of ≈350 mm. The transition occurs when the beam energy exceeds a threshold value between 145 and 170 eV. Low-level hysteresis is observed in the transition when E(ib) is being reduced. The radial profiles of the ion beam current density and the low temperature ion current density can be obtained separately using a Faraday cup with a grid in front. The measured profiles confirm that more than a half of the extracted beam ions reaches the target plate with a good focusing profile with a full width at half maximum of ≈3 cm. Estimation of the particle balances in beam ions, the slow ions, and the electrons indicates the possibility that the secondary electron emission from the target plate and electron impact ionization of hydrogen may play roles as particle sources in this extremely low-energy beam after the compensation of beam ion space charge. PMID:26628125

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

    SciTech Connect

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

    2015-11-15

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

  2. Sensitivities in the production of spread-out Bragg peak dose distributions by passive scattering with beam current modulation

    SciTech Connect

    Lu, H.-M.; Brett, Robert; Engelsman, Martijn; Slopsema, Roelf; Kooy, Hanne; Flanz, Jay

    2007-10-15

    A spread-out Bragg peak (SOBP) is used in proton beam therapy to create a longitudinal conformality of the required dose to the target. In order to create this effect in a passive beam scattering system, a variety of components must operate in conjunction to produce the desired beam parameters. We will describe how the SOBP is generated and will explore the tolerances of the various components and their subsequent effect on the dose distribution. A specific aspect of this investigation includes a case study involving the use of a beam current modulated system. In such a system, the intensity of the beam current can be varied in synchronization with the revolution of the range-modulator wheel. As a result, the weights of the pulled-back Bragg peaks can be individually controlled to produce uniform dose plateaus for a large range of treatment depths using only a small number of modulator wheels.

  3. Surface modification of 40CrNiMo7 steel with high current pulsed electron beam treatment

    NASA Astrophysics Data System (ADS)

    Hao, Shengzhi; Wang, Huihui; Zhao, Limin

    2016-02-01

    High current pulsed electron beam (HCPEB) treatment was conducted on 40CrNiMo7 steel with accelerating voltage 27 kV, energy density 3 J/cm2, pulse duration 2.5 μs and 1-50 pulses. The evolutions of surface microstructure were investigated by using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) techniques. It was found that the carbides in the surface remelted layer of depth ∼4 μm were dissolved gradually along with the increasing number of HCPEB pulses. Eventually, the surface microstructure of 40CrNiMo7 steel was transformed to a complex structure composed of very refined ∼150 nm austenite as the main part and a little quantity of martensite phases. After 15 pulses of HCPEB treatment, the surface microhardness was doubled to 553 HV, and the wear rate decreased to one third of the initial state correspondingly.

  4. High-resolution velocimetry in energetic tidal currents using a convergent-beam acoustic Doppler profiler

    NASA Astrophysics Data System (ADS)

    Sellar, Brian; Harding, Samuel; Richmond, Marshall

    2015-08-01

    An array of single-beam acoustic Doppler profilers has been developed for the high resolution measurement of three-dimensional tidal flow velocities and subsequently tested in an energetic tidal site. This configuration has been developed to increase spatial resolution of velocity measurements in comparison to conventional acoustic Doppler profilers (ADPs) which characteristically use divergent acoustic beams emanating from a single instrument. This is achieved using geometrically convergent acoustic beams creating a sample volume at the focal point of 0.03 m3. Away from the focal point, the array is also able to simultaneously reconstruct three-dimensional velocity components in a profile throughout the water column, and is referred to herein as a convergent-beam acoustic Doppler profiler (C-ADP). Mid-depth profiling is achieved through integration of the sensor platform with the operational commercial-scale Alstom 1 MW DeepGen-IV Tidal Turbine deployed at the European Marine Energy Center, Orkney Isles, UK. This proof-of-concept paper outlines the C-ADP system configuration and comparison to measurements provided by co-installed reference instrumentation. Comparison of C-ADP to standard divergent ADP (D-ADP) velocity measurements reveals a mean difference of 8 mm s-1, standard deviation of 18 mm s-1, and an order of magnitude reduction in realisable length scale. C-ADP focal point measurements compared to a proximal single-beam reference show peak cross-correlation coefficient of 0.96 over 4.0 s averaging period and a 47% reduction in Doppler noise. The dual functionality of the C-ADP as a profiling instrument with a high resolution focal point make this configuration a unique and valuable advancement in underwater velocimetry enabling improved quantification of flow turbulence. Since waves are simultaneously measured via profiled velocities, pressure measurements and surface detection, it is expected that derivatives of this system will be a powerful tool in

  5. An accurate online calibration system based on combined clamp-shape coil for high voltage electronic current transformers.

    PubMed

    Li, Zhen-hua; Li, Hong-bin; Zhang, Zhi

    2013-07-01

    Electronic transformers are widely used in power systems because of their wide bandwidth and good transient performance. However, as an emerging technology, the failure rate of electronic transformers is higher than that of traditional transformers. As a result, the calibration period needs to be shortened. Traditional calibration methods require the power of transmission line be cut off, which results in complicated operation and power off loss. This paper proposes an online calibration system which can calibrate electronic current transformers without power off. In this work, the high accuracy standard current transformer and online operation method are the key techniques. Based on the clamp-shape iron-core coil and clamp-shape air-core coil, a combined clamp-shape coil is designed as the standard current transformer. By analyzing the output characteristics of the two coils, the combined clamp-shape coil can achieve verification of the accuracy. So the accuracy of the online calibration system can be guaranteed. Moreover, by employing the earth potential working method and using two insulating rods to connect the combined clamp-shape coil to the high voltage bus, the operation becomes simple and safe. Tests in China National Center for High Voltage Measurement and field experiments show that the proposed system has a high accuracy of up to 0.05 class. PMID:23902112

  6. An accurate online calibration system based on combined clamp-shape coil for high voltage electronic current transformers

    SciTech Connect

    Li, Zhen-hua; Li, Hong-bin; Zhang, Zhi

    2013-07-15

    Electronic transformers are widely used in power systems because of their wide bandwidth and good transient performance. However, as an emerging technology, the failure rate of electronic transformers is higher than that of traditional transformers. As a result, the calibration period needs to be shortened. Traditional calibration methods require the power of transmission line be cut off, which results in complicated operation and power off loss. This paper proposes an online calibration system which can calibrate electronic current transformers without power off. In this work, the high accuracy standard current transformer and online operation method are the key techniques. Based on the clamp-shape iron-core coil and clamp-shape air-core coil, a combined clamp-shape coil is designed as the standard current transformer. By analyzing the output characteristics of the two coils, the combined clamp-shape coil can achieve verification of the accuracy. So the accuracy of the online calibration system can be guaranteed. Moreover, by employing the earth potential working method and using two insulating rods to connect the combined clamp-shape coil to the high voltage bus, the operation becomes simple and safe. Tests in China National Center for High Voltage Measurement and field experiments show that the proposed system has a high accuracy of up to 0.05 class.

  7. Application of Hilbert-Huang transform for defect recognition in pulsed eddy current testing

    NASA Astrophysics Data System (ADS)

    Liu, Baoling; Huang, Pingjie; Hou, Dibo; Chen, Xiao; Zhang, Guangxin

    2015-07-01

    Defect recognition plays an important role in the structure integrity and health monitor of in-service equipment. However, it is difficult to recognise deep-layer defect or small-size defect in conductive structure during pulsed eddy current (PEC) testing. Aiming at the issue, this article proposes a method based on Hilbert-Huang transform which consists of two modules: data processing and defect recognition. In the data processing module, the PEC response signal is decomposed into a few of intrinsic mode functions (IMFs) using ensemble empirical mode decomposition method. The IMFs whose variance contribution rates are bigger than 1% are chosen to reconstruct signal in order to remove noise. In the defect recognition module, the features based on specific frequency components of marginal spectrum (MS) of the reconstructed signals are extracted to discriminate those defects in surface and subsurface. Furthermore, the normalisation MS energy ratio is proposed to quantify defects which cannot be distinguished using peak value in time domain. Experiments show that the proposed method can achieve better de-noising effect and defect evaluation, which contributes to the recognition of those complicated defects such as deep-layered and small-sized defect.

  8. Cathode performance during two beam operation of the high current high polarization electron gun for eRHIC

    SciTech Connect

    Rahman, O.; Ben-Zvi, I.; Degen, C.; Gassner, D. M.; Lambiase, R.; Meng, W.; Pikin, A.; Rao, T.; Sheehy, B.; Skaritka, J.; Wang, E.; Pietz, J.; Ackeret, M.; Yeckel, C.; Miller, R.; Dobrin, E.; Thompson, K.

    2015-05-03

    Two electron beams from two activated bulk GaAs photocathodes were successfully combined during the recent beam test of the High Current High Polarization Electron gun for eRHIC. The beam test took place in Stangenes Industries in Palo Alto, CA, where the cathodes were placed in diagonally opposite locations inside the high voltage shroud. No significant cross talking between the cathodes was found for the pertinent vacuum and low average current operation, which is very promising towards combining multiple beams for higher average current. This paper describes the cathode preparation, transport and cathode performance in the gun for the combining test, including the QE and lifetimes of the photocathodes at various steps of the experiment.

  9. Electron beam dynamics in the long-pulse, high-current DARHT-II linear induction accelerator

    SciTech Connect

    Ekdahl, Carl A; Abeyta, Epifanio O; Aragon, Paul; Archuleta, Rita; Cook, Gerald; Dalmas, Dale; Esquibel, Kevin; Gallegos, Robert A; Garnett, Robert; Harrison, James F; Johnson, Jeffrey B; Jacquez, Edward B; Mccuistian, Brian T; Montoya, Nicholas A; Nath, Subrato; Nielsen, Kurt; Oro, David; Prichard, Benjamin; Rowton, Lawrence; Sanchez, Manolito; Scarpetti, Raymond; Schauer, Martin M; Seitz, Gerald; Schulze, Martin; Bender, Howard A; Broste, William B; Carlson, Carl A; Frayer, Daniel K; Johnson, Douglas E; Tom, C Y; Williams, John; Hughes, Thomas; Anaya, Richard; Caporaso, George; Chambers, Frank; Chen, Yu - Jiuan; Falabella, Steve; Guethlein, Gary; Raymond, Brett; Richardson, Roger; Trainham, C; Weir, John; Genoni, Thomas; Toma, Carsten

    2009-01-01

    The DARHT-II linear induction accelerator (LIA) now accelerates 2-kA electron beams to more than 17 MeV. This LIA is unique in that the accelerated current pulse width is greater than 2 microseconds. This pulse has a flat-top region where the final electron kinetic energy varies by less than 1% for more than 1.5 microseconds. The long risetime of the 6-cell injector current pulse is 0.5 {micro}s, which can be scraped off in a beam-head cleanup zone before entering the 68-cell main accelerator. We discuss our experience with tuning this novel accelerator; and present data for the resulting beam transport and dynamics. We also present beam stability data, and relate these to previous stability experiments at lower current and energy.

  10. Transformation of the vortex beam in the optical vortex scanning microscope

    NASA Astrophysics Data System (ADS)

    Płociniczak, Łukasz; Popiołek-Masajada, Agnieszka; Szatkowski, Mateusz; Wojnowski, Dariusz

    2016-07-01

    We investigate the microscopic system in which the Gaussian beam with embedded optical vortex is used. The optical vortex is introduced by vortex lens. The vortex lens shift induces a precise nanometer shift of the embedded vortices inside the focused spot. The analytical formula for the complex amplitude of the focused spot with off-axis vortex was calculated, to our knowledge, for the first time. This solution is an important step in the development of the optical vortex scanning microscope. Experimental results are also presented that demonstrate the behavior of such a beam in an experimental setup.

  11. Focusing of high-current, large-area, heavy-ion beams with an electrostatic plasma lens

    SciTech Connect

    Goncharov, A.A.; Protsenko, I.M.; Yushkov, G.Y.; Brown, I.G.

    1999-08-01

    We report on measurements of the focusing of high-current, large-area beams of heavy metal ions using an electrostatic plasma lens. Tantalum ion beams were formed by a repetitively pulsed vacuum arc ion source, with energy in the 100 keV range, current up to 0.5 A, initial beam diameter 10 cm, and pulse length 250 {mu}s. The plasma lens was of internal diameter 10 cm and length 20 cm, and had nine electrostatic ring electrodes with potential applied to the central electrode of up to 7 kV, in the presence of a pulsed magnetic field of up to 800 G. The current-density profile of the downstream, focused, ion beam was measured with a radially moveable, magnetically suppressed, Faraday cup. The tantalum ion-beam current density at the focus was compressed by a factor of up to 30. The results are important in that they provide a demonstration of a means of manipulating high-current ion beams without associated space-charge blowup. {copyright} {ital 1999 American Institute of Physics.}

  12. Two-stream Stability Properties of the Return-Current Layer for Intense Ion Beam Propagation Through Background Plasma

    SciTech Connect

    Edward A. Startsev, Ronald C. Davidson and Mikhail Dorf

    2009-09-10

    When an ion beam with sharp edge propagates through a background plasma, its current is neutralized by the plasma return current everywhere except at the beam edge over a characteristic transverse distance Δχ⊥ ~ δpe, where δpe = c/ωpe is the collisionless skin depth, and ωpe is the electron plasma frequency. Because the background plasma electrons neutralizing the ion beam current inside the beam are streaming relative to the background plasma electrons outside the beam, the background plasma can support a two-stream surface-mode excitation. Such surface modes have been studied previously assuming complete charge and current neutralization, and have been shown to be strongly unstable. In this paper we study the detailed stability properties of this two-stream surface mode for an electron flow velocity profile self-consistently driven by the ion beam. In particular, it is shown that the self-magnetic field generated inside the unneutralized current layer, which has not been taken into account previously, completely eliminates the instability.

  13. Impact of quasi-dc currents on three-phase distribution transformer installations. Power Systems Technology Program

    SciTech Connect

    McConnell, B.W.; Barnes, P.R.; Tesche, F.M.; Schafer, D.A.

    1992-06-01

    This report summarizes a series of tests designed to determine the response of quasi-dc currents on three-phase power distribution transformers for electric power systems. In general, if the dc injection is limited to the primary side of a step-down transformer, significant harmonic distortion is noted and an increase in the reactive power demand results. For dc injection on the secondary (load) side of the step-down transformer the harmonic content at the secondary side is quite high and saturation occurs with a relatively low level of dc injection; however, the reactive power demand is significantly lower. These tests produced no apparent damage to the transformers. Transformer damage is dependent on the duration of the dc excitation, the level of the excitation, and on thermal characteristics of the transfer. The transformer response time is found to be much shorter than seen in power transformer tests at lower dc injection levels. This shorter response time suggests that the response time is strongly dependent on the injected current levels, and that higher levels of dc injection for shorter durations could produce very high reactive power demands and harmonic distortion within a few tenths of a second. The added reactive power load could result in the blowing of fuses on the primary side of the transformer for even moderate dc injection levels, and neutral currents are quite large under even low-level dc injection. This ``smoking neutral`` results in high-level harmonic injection into equipment via the neutral and in possible equipment failure.

  14. Graphitic cage transformation by electron-beam-induced catalysis with alkali-halide nanocrystals

    NASA Astrophysics Data System (ADS)

    Fujita, Jun-ichi; Tachi, Masashi; Ito, Naoto; Murakami, Katsuhisa; Takeguchi, Masaki

    2016-05-01

    We found that alkali-halide nanocrystals, such as KCl and NaCl, have strong catalytic capability to form graphitic carbon cages from amorphous carbon shells under electron beam irradiation. In addition to the electron beam irradiation strongly inducing the decomposition of alkali-halide nanocrystals, graphene fragments were formed and linked together to form the final product of thin graphitic carbon cages after the evaporation of alkali-halide nanocrystals. The required electron dose was approximately 1 to 20 C/cm2 at 120 keV at room temperature, which was about two orders of magnitude smaller than that required for conventional beam-induced graphitization. The “knock-on” effect of primary electrons strongly induced the decomposition of the alkali-halide crystal inside the amorphous carbon shell. However, the strong ionic cohesion quickly reformed the crystal into thin layers inside the amorphous shell. The bond excitation induced by the electron beam irradiation seemed to enhance strongly the graphitization at the interface between the outer amorphous carbon shell and the inner alkali-halide crystal.

  15. Wide Dynamic Range Front-end Electronics for Beam Current and Position Measurement

    SciTech Connect

    Rawnsley, W. R.; Potter, R. J.; Verzilov, V. A.; Root, L.

    2006-11-20

    An Analog Devices log detector, AD8306, and a Digital Signal Processor (DSP), ADSP-21992, have been found useful for building wide dynamic range, accurate and inexpensive front-end electronics to measure and process the RF signals from TRIUMF's beam monitors. The high-precision log detector has a useful dynamic range of over 100 dB. The 160 MHz mixed-signal DSP is used to digitize the log detector output, linearize it via a lookup table, perform temperature compensation, and remove the variable duty cycle 1 kHz pulse structure of the beam. This approach has been applied to two types of devices in a 500 MeV proton beamline. The 0.1% DC to CW total current monitor is based on a capacitive pickup resonant at 46.11 MHz, the second harmonic of the bunch frequency. The DSP software provides low pass filtering, calculates the antilog of the data and passes the output to a CAMAC input register. The BPM electronics process data from inductive pickup loops. The DSP controls a GaAs switch which multiplexes signals from four adjacent pickups to a single log detector. The DSP performs difference-over-sum or log-ratio data analysis along with averaging over an arbitrary number of samples.

  16. Transient analysis and control of bias magnetic state in the transformer of on-line pulse-width-modulation switching full bridge direct current-direct current converter

    NASA Astrophysics Data System (ADS)

    Chen, Jiaxin; Guo, Youguang; Zhu, Jianguo; Wei Lin, Zhi

    2012-04-01

    This paper presents a finite element analysis (FEA) based method for analyzing and controlling the bias magnetic state of the transformer of a pulse-width-modulation (PWM) switching full bridge dc-dc converter. A field-circuit indirect coupling method for predicting the transient bias magnetic state is introduced first. To increase flexibility of the proposed method, a novel transformer model which can address not only its basic input-output characteristic, but also the nonlinear magnetizing inductance, is proposed. Both the asymmetric characteristic and the variable laws of the current flowing through the two secondary windings during the period of PWM switching-off state are highlighted. Finally, the peak magnetizing current controlled method based on the on-line magnetizing current computation is introduced. Analysis results show that this method can address the magnetic saturation at winding ends, and hence many previous difficulties, such as the start-up process and asymmetry of power electronics, can be easily controlled.

  17. Practical Framework for an Electron Beam Induced Current Technique Based on a Numerical Optimization Approach

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hideshi; Soeda, Takeshi

    2015-03-01

    A practical framework for an electron beam induced current (EBIC) technique has been established for conductive materials based on a numerical optimization approach. Although the conventional EBIC technique is useful for evaluating the distributions of dopants or crystal defects in semiconductor transistors, issues related to the reproducibility and quantitative capability of measurements using this technique persist. For instance, it is difficult to acquire high-quality EBIC images throughout continuous tests due to variation in operator skill or test environment. Recently, due to the evaluation of EBIC equipment performance and the numerical optimization of equipment items, the constant acquisition of high contrast images has become possible, improving the reproducibility as well as yield regardless of operator skill or test environment. The technique proposed herein is even more sensitive and quantitative than scanning probe microscopy, an imaging technique that can possibly damage the sample. The new technique is expected to benefit the electrical evaluation of fragile or soft materials along with LSI materials.

  18. Stability of a current carrying single nanowire of tungsten (W) deposited by focused ion beam

    NASA Astrophysics Data System (ADS)

    Mandal, Pabitra; Das, Bipul; Raychaudhuri, A. K.

    2016-02-01

    We report an investigation on the stability of single W nanowire (NW) under direct current stressing. The NW of width ≈ 80 nm and thickness ≈ 100 nm was deposited on a SiO2/Si substrate by Focused Ion Beam (FIB) of Ga ions using W(CO)6 as a precursor. Such nanowires, used as interconnects in nanoelectronics, contain C and Ga in addition to W. The stability studies, done for the first time in such FIB deposited NWs, show that under current stressing these NWs behave very differently from that observed in conventional metal NWs or interconnects. The failure of such FIB deposited NW occurs at a relatively low current density (˜1011 A/m2) which is an order or more less than that seen in conventional metal NWs. The failure accompanies with formation of voids and hillocks, suggesting ionic migration as the cause of failure. However, the polarities of void and hillock formations are opposite to those observed in conventional metal interconnects. This observation along with preferential agglomeration of Ga ions in hillocks suggests that the ionic migration in such NWs is dominated by direct force as opposed to the migration driven by electron wind force in conventional metal interconnects.

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

    SciTech Connect

    Xu Qifu; Liu Lie

    2012-09-15

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

  20. Electron Beam Return-Current Losses in Solar Flares: Initial Comparison of Analytical and Numerical Results

    NASA Technical Reports Server (NTRS)

    Holman, Gordon

    2010-01-01

    Accelerated electrons play an important role in the energetics of solar flares. Understanding the process or processes that accelerate these electrons to high, nonthermal energies also depends on understanding the evolution of these electrons between the acceleration region and the region where they are observed through their hard X-ray or radio emission. Energy losses in the co-spatial electric field that drives the current-neutralizing return current can flatten the electron distribution toward low energies. This in turn flattens the corresponding bremsstrahlung hard X-ray spectrum toward low energies. The lost electron beam energy also enhances heating in the coronal part of the flare loop. Extending earlier work by Knight & Sturrock (1977), Emslie (1980), Diakonov & Somov (1988), and Litvinenko & Somov (1991), I have derived analytical and semi-analytical results for the nonthermal electron distribution function and the self-consistent electric field strength in the presence of a steady-state return-current. I review these results, presented previously at the 2009 SPD Meeting in Boulder, CO, and compare them and computed X-ray spectra with numerical results obtained by Zharkova & Gordovskii (2005, 2006). The phYSical significance of similarities and differences in the results will be emphasized. This work is supported by NASA's Heliophysics Guest Investigator Program and the RHESSI Project.

  1. Design and characterization of the annular cathode high current pulsed electron beam source for circular components

    NASA Astrophysics Data System (ADS)

    Jiang, Wei; Wang, Langping; Wang, Xiaofeng

    2016-08-01

    In order to irradiate circular components with high current pulsed electron beam (HCPEB), an annular cathode based on carbon fiber bunches was designed and fabricated. Using an acceleration voltage of 25 kV, the maximum pulsed irradiation current and energy of this annular cathode can reach 7.9 kA and 300 J, respectively. The irradiation current density distribution of the annular cathode HCPEB source measured along the circumferential direction shows that the annular cathode has good emission uniformity. In addition, four 9310 steel substrates fixed uniformly along the circumferential direction of a metal ring substrate were irradiated by this annular cathode HCPEB source. The surface and cross-section morphologies of the irradiated samples were characterized by scanning electron microscopy (SEM). SEM images of the surface reveal that crater and surface undulation have been formed, which hints that the irradiation energy of the HCPEB process is large enough for surface modification of 9310 steel. Meanwhile, SEM cross-section images exhibit that remelted layers with a thickness of about 5.4 μm have been obtained in all samples, which proves that a good practical irradiation uniformity can be achieved by this annular cathode HCPEB source.

  2. The current status of cone beam computed tomography imaging in orthodontics

    PubMed Central

    Kapila, S; Conley, R S; Harrell, W E

    2011-01-01

    Cone beam CT (CBCT) has become an increasingly important source of three dimensional (3D) volumetric data in clinical orthodontics since its introduction into dentistry in 1998. The purpose of this manuscript is to highlight the current understanding of, and evidence for, the clinical use of CBCT in orthodontics, and to review the findings to answer clinically relevant questions. Currently available information from studies using CBCT can be organized into five broad categories: 1, the assessment of CBCT technology; 2, its use in craniofacial morphometric analyses; 3, incidental and missed findings; 4, analysis of treatment outcomes; and 5, efficacy of CBCT in diagnosis and treatment planning. The findings in these topical areas are summarized, followed by current indications and protocols for the use of CBCT in specific cases. Despite the increasing popularity of CBCT in orthodontics, and its advantages over routine radiography in specific cases, the effects of information derived from these images in altering diagnosis and treatment decisions has not been demonstrated in several types of cases. It has therefore been recommended that CBCT be used in select cases in which conventional radiography cannot supply satisfactory diagnostic information; these include cleft palate patients, assessment of unerupted tooth position, supernumerary teeth, identification of root resorption and for planning orthognathic surgery. The need to image other types of cases should be made on a case-by-case basis following an assessment of benefits vs risks of scanning in these situations. PMID:21159912

  3. Beam-folding ultraviolet-visible Fourier transform spectrometry and underwater cytometry for in situ measurement of marine phytoplankton

    NASA Astrophysics Data System (ADS)

    Wang, Xuzhu

    The system complexity and hence high cost needed for generating the high-resolution and precise position-sampling triggers over very long distances is one of main hindrances to the popularization of the UV-visible Fourier transform spectrometer (FTS). In part one of this thesis, the specially designed beam-folding and improved beam-folding methods to optically subdivide the laser fringes are presented. The Near-UV to Near-infrared FTSs based on 4-fold beam-folding systems were developed. The experimental results have demonstrated that these techniques are promising methods to produce the high-resolution and high-precision sampling triggers of scanning mechanism of UV-visible FTSs without the need for complicated optics, sophisticated detector electronics and high-stability motion control systems. The FTS based on the beam-folding technique can reach a spectral resolution of ˜4 cm-1 (0.1nm) in the visible wavelengths; The FTS based on the improved beam-folding technique can achieve a spectral resolution of ˜0.28 cm-1 (0.01nm) in the visible wavelengths. In the improved beam-folding FTS, The adoption of retroreflectors and the symmetrical arrangement of two back-to back interferometers produced much higher performance than that of the beam-folding FTS employing prism mirrors. The replacement of prism mirrors by retroreflectors and the symmetrical optical arrangement maintain the FTS in perfect optical alignment during scanning process by keeping all beams parallel with the incident beams. The vertex of the movable retroreflector in the measurement interferometer is arranged very close to the midpoint of the vertices of the movable retroreflectors in the tracking interferometer so that the optical symmetrical axes for both interferometers always keep in line with each other. That is, the change of the OPD of the tracking interferometer always remains synchronous to that of the OPD of the measurement interferometer even for any moving misalignments, making the FTS

  4. Degradation and decoloration of textiles wastewater by electron beam irradiation: Effect of energy, current and absorbed dose

    SciTech Connect

    Bakar, Khomsaton Abu; Zulkafli,; Hashim, Siti A'aisah; Ahmad, Pauzi

    2014-09-03

    In this study, electron beam accelerator (EB) was used to treat textiles wastewater from Rawang Industrial Park, Selangor. The objectives were to determine effective energy, beam current and absorbed dose required for decoloration and degradation of the textiles effluent. The textiles effluent was irradiated in a batch with various energy of 1MeV to 3MeV at constant beam current of 30mA. It was observed that removal of color and COD increases with higher beam energy. The EB energy of 1MeV effectively to removed 58% color and 19% COD. For textile effluent sample irradiated at fix energy of 1MeV and 3Mev but at different beam current 10mA, 20mA and 30mA. It was observed that removal of color and COD increases with the increased of beam current at each energy. However removal of color was significantly better at 1Mev as compared to 3Mev. In the case of textiles effluent, irradiated at doses of 17, 20,25,30, 35, 100 and 200kGy using 30 kW power of EB (1Mev, 30mA), results shows removal of BOD{sub 5}, COD and color were in the range 9%-33%, 14%-38% and 43%-78% respectively.

  5. A high-current electron gun for the electron beam ion trap at the National Superconducting Cyclotron Laboratory

    SciTech Connect

    Schwarz, S. Baumann, T. M.; Kittimanapun, K.; Lapierre, A.; Snyder, A.

    2014-02-15

    The Electron Beam Ion Trap (EBIT) in NSCL’s reaccelerator ReA uses continuous ion injection and accumulation. In order to maximize capture efficiency and minimize breeding time into high charge states, the EBIT requires a high-current/high current-density electron beam. A new electron gun insert based on a concave Ba-dispenser cathode has been designed and built to increase the current transmitted through the EBIT’s superconducting magnet. With the new insert, stable EBIT operating conditions with 0.8 A of electron beam have been established. The design of the electron gun is presented together with calculated and measured perveance data. In order to assess the experimental compression of the electron beam, a pinhole CCD camera has been set up to measure the electron beam radius. The camera observes X-rays emitted from highly charged ions, excited by the electron beam. Initial tests with this camera setup will be presented. They indicate that a current density of 640 A/cm{sup 2} has been reached when the EBIT magnet was operated at 4 T.

  6. A high-current electron gun for the electron beam ion trap at the National Superconducting Cyclotron Laboratory.

    PubMed

    Schwarz, S; Baumann, T M; Kittimanapun, K; Lapierre, A; Snyder, A

    2014-02-01

    The Electron Beam Ion Trap (EBIT) in NSCL's reaccelerator ReA uses continuous ion injection and accumulation. In order to maximize capture efficiency and minimize breeding time into high charge states, the EBIT requires a high-current/high current-density electron beam. A new electron gun insert based on a concave Ba-dispenser cathode has been designed and built to increase the current transmitted through the EBIT's superconducting magnet. With the new insert, stable EBIT operating conditions with 0.8 A of electron beam have been established. The design of the electron gun is presented together with calculated and measured perveance data. In order to assess the experimental compression of the electron beam, a pinhole CCD camera has been set up to measure the electron beam radius. The camera observes X-rays emitted from highly charged ions, excited by the electron beam. Initial tests with this camera setup will be presented. They indicate that a current density of 640 A/cm(2) has been reached when the EBIT magnet was operated at 4 T. PMID:24593604

  7. A high-current electron gun for the electron beam ion trap at the National Superconducting Cyclotron Laboratory

    NASA Astrophysics Data System (ADS)

    Schwarz, S.; Baumann, T. M.; Kittimanapun, K.; Lapierre, A.; Snyder, A.

    2014-02-01

    The Electron Beam Ion Trap (EBIT) in NSCL's reaccelerator ReA uses continuous ion injection and accumulation. In order to maximize capture efficiency and minimize breeding time into high charge states, the EBIT requires a high-current/high current-density electron beam. A new electron gun insert based on a concave Ba-dispenser cathode has been designed and built to increase the current transmitted through the EBIT's superconducting magnet. With the new insert, stable EBIT operating conditions with 0.8 A of electron beam have been established. The design of the electron gun is presented together with calculated and measured perveance data. In order to assess the experimental compression of the electron beam, a pinhole CCD camera has been set up to measure the electron beam radius. The camera observes X-rays emitted from highly charged ions, excited by the electron beam. Initial tests with this camera setup will be presented. They indicate that a current density of 640 A/cm2 has been reached when the EBIT magnet was operated at 4 T.

  8. Quantitative description of the properties of extended defects in silicon by means of electron- and laser-beam-induced currents

    SciTech Connect

    Shabelnikova, Ya. L. Yakimov, E. B.; Nikolaev, D. P.; Chukalina, M. V.

    2015-06-15

    A solar cell on a wafer of multicrystalline silicon containing grain boundaries was studied by the induced-current method. The sample was scanned by an electron beam and by a laser beam at two wavelengths (980 and 635 nm). The recorded induced-current maps were aligned by means of a specially developed code, that enabled to analyze the same part of the grain boundary for three types of measurements. Optimization of the residual between simulated induced-current profiles and those obtained experimentally yielded quantitative estimates of the characteristics of a sample and its defects: the diffusion length of minority carriers and recombination velocity at the grain boundary.

  9. CONTROL SYSTEM FOR THE LITHIUM BEAM EDGE PLASMA CURRENT DENSITY DIAGNOSTIC ON THE DIII-D TOKAMAK

    SciTech Connect

    PEAVY,J.J; CARY,W.P; THOMAS,D.M; KELLMAN,D.H; HOYT,D.M; DELAWARE,S.W; PRONKO,S.G.E; HARRIS,T.E

    2003-10-01

    OAK-B135 An edge plasma current density diagnostic employing a neutralized lithium ion beam system has been installed on the DIII-D tokamak. The lithium beam control system is designed around a GE Fanuc 90-30 series PLC and Cimplicity{reg_sign} HMI (Human Machine Interface) software. The control system operates and supervises a collection of commercial and in-house designed high voltage power supplies for beam acceleration and focusing, filament and bias power supplies for ion creation, neutralization, vacuum, triggering, and safety interlocks. This paper provides an overview of the control system, while highlighting innovative aspects including its remote operation, pulsed source heating and pulsed neutralizer heating, optimizing beam regulation, and beam ramping, ending with a discussion of its performance.

  10. Extended wavelet transformation to digital holographic reconstruction: application to the elliptical, astigmatic Gaussian beams.

    PubMed

    Remacha, Clément; Coëtmellec, Sébastien; Brunel, Marc; Lebrun, Denis

    2013-02-01

    Wavelet analysis provides an efficient tool in numerous signal processing problems and has been implemented in optical processing techniques, such as in-line holography. This paper proposes an improvement of this tool for the case of an elliptical, astigmatic Gaussian (AEG) beam. We show that this mathematical operator allows reconstructing an image of a spherical particle without compression of the reconstructed image, which increases the accuracy of the 3D location of particles and of their size measurement. To validate the performance of this operator we have studied the diffraction pattern produced by a particle illuminated by an AEG beam. This study used mutual intensity propagation, and the particle is defined as a chirped Gaussian sum. The proposed technique was applied and the experimental results are presented. PMID:23385926

  11. Influence of beam shape on in-vitro cellular transformations in human skin fibroblasts

    NASA Astrophysics Data System (ADS)

    Mthunzi, Patience; Forbes, Andrew; Hawkins, Denise; Abrahamse, Heidi; Karsten, Aletta E.

    2005-08-01

    A variety of strategies have been utilised for prevention and treatment of chronic wounds such as leg ulcers, diabetic foot ulcers and pressure sores1. Low Level Laser Therapy (LLLT) has been reported to be an invaluable tool in the enhancement of wound healing through stimulating cell proliferation, accelerating collagen synthesis and increasing ATP synthesis in mitochondria to name but a few2. This study focused on an in-vitro analysis of the cellular responses induced by treatment with three different laser beam profiles namely, the Gaussian (G), Super Gaussian (SG) and Truncated Gaussian (TG), on normal wounded irradiated (WI) and wounded non-irradiated (WNI) human skin fibroblast cells (WS1), to test their influence in wound healing at 632.8 nm using a helium neon (HeNe) laser. For each beam profile, measurements were made using average energy densities over the sample ranging from 0.2 to 1 J, with single exposures on normal wounded cells. The cells were subjected to different post irradiation incubation periods, ranging from 0 to 24 hours to evaluate the duration (time) dependent effects resulting from laser irradiation. The promoted cellular alterations were measured by increase in cell viability, cell proliferation and cytotoxicity. The results obtained showed that treatment with the G compared to the SG and TG beams resulted in a marked increase in cell viability and proliferation. The data also showed that when cells undergo laser irradiation some cellular processes are driven by the peak energy density rather than the energy of the laser beam. We show that there exist threshold values for damage, and suggest optimal operating regimes for laser based wound healing.

  12. Mixed eccentricity diagnosis in Inverter-Fed Induction Motors via the Adaptive Slope Transform of transient stator currents

    NASA Astrophysics Data System (ADS)

    Pons-Llinares, J.; Antonino-Daviu, J.; Roger-Folch, J.; Moríñigo-Sotelo, D.; Duque-Pérez, O.

    2014-10-01

    This paper researches the detection of mixed eccentricity in Inverter-Fed Induction Motors. The classic FFT method cannot be applied when the stator current captured is not in steady state, which is very common in these motors. Therefore, a transform able to detect the time-frequency evolutions of the components present in the transient signal captured must be applied. In order to optimize the result, a method to calculate the theoretical time-frequency evolution of the stator current components is presented, using only the captured current. This previously obtained information enables the use of the proposed transform: the Adaptive Slope Transform, based on appropriately choosing the atom slope in each point analyzed. Thanks to its adaptive characteristics, the time-frequency evolution of the main components in a stator transient current is traced precisely and with high detail in the 2D time-frequency plot obtained. As a consequence, the time-frequency plane characteristic patterns produced by the Eccentricity Related Harmonics are easily and clearly identified enabling a reliable diagnosis. Moreover, the problem of quantifying the presence of the fault is solved presenting a simple and easy to apply method. The transform capabilities have been shown successfully diagnosing an Inverter-Fed Induction Motor with mixed eccentricity during a startup, a decrease in the assigned frequency, and a load variation with and without slip compensation.

  13. Current role of hybrid CT/angiography system compared with C-arm cone beam CT for interventional oncology

    PubMed Central

    Arai, Y; Inaba, Y; Inoue, M; Nishiofuku, H; Anai, H; Hori, S; Sakaguchi, H; Kichikawa, K

    2014-01-01

    Hybrid CT/angiography (angiography) system and C-arm cone beam CT provide cross-sectional imaging as an adjunct to angiography. Current interventional oncological procedures can be conducted precisely using these two technologies. In this article, several cases using a hybrid CT/angiography system are shown first, and then the advantages and disadvantages of the hybrid CT/angiography and C-arm cone beam CT are discussed with literature reviews. PMID:24968749

  14. Note: Measurement of extreme-short current pulse duration of runaway electron beam in atmospheric pressure air

    SciTech Connect

    Tarasenko, V. F.; Rybka, D. V.; Burachenko, A. G.; Lomaev, M. I.; Balzovsky, E. V.

    2012-08-15

    This note reports the time-amplitude characteristic of the supershort avalanche electron beam with up to 20 ps time resolution. For the first time it is shown that the electron beam downstream of small-diameter diaphragms in atmospheric pressure air has a complex structure which depends on the interelectrode gap width and cathode design. With a spherical cathode and collimator the minimum duration at half maximum of the supershort avalanche electron beam current pulse was shown to be {approx}25 ps. The minimum duration at half maximum of one peak in the pulses with two peaks can reach {approx}25 ps too.

  15. Gated current integrator for the beam in the RR barrier buckets

    SciTech Connect

    A. Cadorn; C. Bhat; J. Crisp

    2003-06-10

    At the Fermilab Recycler Ring (RR), the antiproton (pbar) beam will be stored azimuthally in different segments created by barrier buckets. The beam in each segment may have widely varying intensities. They have developed a gated integrator system to measure the beam intensity in each of the barrier bucket. Here they discuss the design of the system and the results of beam measurements using the integrator.

  16. Pioneering experiments on atomic-beam-assisted generation of drag currents in the Globus-M spherical tokamak

    NASA Astrophysics Data System (ADS)

    Shchegolev, P. B.; Bakharev, N. N.; Gusev, V. K.; Kurskiev, G. S.; Minaev, V. B.; Patrov, M. I.; Petrov, Yu. V.; Sakharov, N. V.

    2015-09-01

    Research data for drag currents in the Globus-M spherical tokamak are presented. The currents are generated by injecting atomic beams of hydrogen and deuterium. Experiments were carried out in the hydrogen and deuterium plasma of the tokamak. It has a divertor configuration with a lower X-point, a displacement along the larger radius from-1.0 to-2.5 cm, and a toroidal field of 0.4 T at a plasma current of 0.17-0.23 MA. The beam is injected into the tokamak in the equatorial plane tangentially to the magnetic axis of the plasma filament with an impact diameter of 32 cm. To provide a 28-keV 0.5-MW atomic beam with geometrical sizes of 4 × 20 cm (at a power level of 1/ e), an IPM-2 ion source is used. The generation of noninductive currents is detected from a rise in the loop current and a simultaneous dip of the loop voltage. The injection of the hydrogen and deuterium atomic beams into the deuterium plasma results in a noticeable and reproducible dip of the loop voltage (up to 0.5 V). Using the ASTRA transport code, a model is constructed that allows rapid calculation of noninductive currents. Calculations performed for a specific discharge confirm that the model adequately describes the effect of drag current generation.

  17. Prospects for Edge Current Density Determination Using Li beam on DIII-D

    SciTech Connect

    D.M. Thomas; A.S. Bozek; T.N. Carlstrom; D.K. Finkenthal; R. Jayakumar; M.A. Makowski; D.G. Nilson; T.H. Osborne; B.W. Rice; R.T. Snider

    2000-08-01

    The specific size and structure of the edge current profile has important effects on the MHD stability and ultimate performance of many advanced tokamak (AT) operating modes. This is true for both bootstrap and externally driven currents that may be used to tailor the edge shear. Absent a direct local measurement of j(r), the best alternative is a determination of the poloidal field. Measurements of the precision (0.1-0.01{sup o} in magnetic pitch angle and 1-10 ms) necessary to address issues of stability and control and provide constraints for EFIT are difficult to do in the region of interest ({rho} = 0.9-1.1). Using Zeeman polarization spectroscopy of the 2S-2P lithium resonance line emission from the DIII-D LIBEAM, measurements of the various field components may be made to the necessary precision in exactly the region of interest to these studies. Because of the negligible Stark mixing of the relevant atomic levels, this method of determining j(r) is insensitive to the large local electric fields typically found in enhanced confinement (H-mode) edges, and thus avoids an ambiguity common to Motional Stark Effect (MSE) measurements of B. Key issues for utilizing this technique include good beam quality, an optimum viewing geometry, and a suitable optical pre-filter to isolate the polarized emission line. A prospective diagnostic system for the DIII-D AT program will be described.

  18. Experimental research of different plasma cathodes for generation of high-current electron beams

    SciTech Connect

    Shafir, G.; Kreif, M.; Gleizer, J. Z.; Gleizer, S.; Krasik, Ya. E.; Gunin, A. V.; Kutenkov, O. P.; Rostov, V. V.; Pegel, I. V.

    2015-11-21

    The results of experimental studies of different types of cathodes—carbon-epoxy rods, carbon-epoxy capillary, edged graphite, and metal-dielectric—under the application of high-voltage pulses with an amplitude of several hundreds of kV and pulse duration of several nanoseconds are presented. The best diode performance was achieved with the edged graphite and carbon-epoxy-based cathodes characterized by uniform and fast (<1 ns) formation of explosive emission plasma spots and quasi-constant diode impedance. This result was achieved for both annular cathodes in a strong magnetic field and planar cathodes of a similar diameter (∼2 cm) with no external magnetic field. The cathodes based on carbon-epoxy rods and carbon-epoxy capillaries operating with an average current density up to 1 kA/cm{sup 2} showed insignificant erosion along 10{sup 6} pulses of the generator and the generated electron beam current showed excellent reproducibility in terms of the amplitude and waveform.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  20. Experimental research of different plasma cathodes for generation of high-current electron beams

    NASA Astrophysics Data System (ADS)

    Shafir, G.; Kreif, M.; Gleizer, J. Z.; Gleizer, S.; Krasik, Ya. E.; Gunin, A. V.; Kutenkov, O. P.; Pegel, I. V.; Rostov, V. V.

    2015-11-01

    The results of experimental studies of different types of cathodes—carbon-epoxy rods, carbon-epoxy capillary, edged graphite, and metal-dielectric—under the application of high-voltage pulses with an amplitude of several hundreds of kV and pulse duration of several nanoseconds are presented. The best diode performance was achieved with the edged graphite and carbon-epoxy-based cathodes characterized by uniform and fast (<1 ns) formation of explosive emission plasma spots and quasi-constant diode impedance. This result was achieved for both annular cathodes in a strong magnetic field and planar cathodes of a similar diameter (˜2 cm) with no external magnetic field. The cathodes based on carbon-epoxy rods and carbon-epoxy capillaries operating with an average current density up to 1 kA/cm2 showed insignificant erosion along 106 pulses of the generator and the generated electron beam current showed excellent reproducibility in terms of the amplitude and waveform.

  1. Characterization of high-current electron beam interaction with metal targets

    SciTech Connect

    An, W.; Krasik, Ya. E.; Fetzer, R.; Bazylev, B.; Mueller, G.; Weisenburger, A.; Bernshtam, V.

    2011-11-01

    The process of electron beam interaction with metal targets was characterized using electrical and optical diagnostics. Electron beams with current density of 5-10 A/cm{sup 2}, electron energy up to 120 keV, pulse duration up to 200 {mu}s, and cross-sectional area of 8-30 cm{sup 2} at the target surface were generated by GESA I and GESA II facilities. Streak imaging of the target surface specular reflectivity was used to determine the onset of melting and re-solidification of the target surface. Using time- and space-resolved schlieren imaging, the evolution of surface irregularities was studied. Experimental and numerical investigations of the neutral flow evaporated from the target surface showed a neutral density of {approx}10{sup 19} cm{sup -3} in the vicinity of the target and neutral velocities up to 2 x 10{sup 5} cm/s. Framing and streak images of visible light emission were used to study the temporal evolution of the target surface plasma and vapors. Time- and space-resolved spectroscopy was applied to determine the surface plasma density and temperature, which were found to be {approx}10{sup 14} cm{sup -3} and {<=}1 eV, respectively. Because of this small plasma density, electric fields in the plasma sheath are not sufficient to cause electrohydrodynamic instability of the liquid target surface. However, hydrodynamic instabilities due to the intense neutral flow observed in experimental and numerical studies are likely to be responsible for the growth of wavelike irregularities.

  2. Production of high current proton beams using complex H-rich molecules at GSI

    NASA Astrophysics Data System (ADS)

    Adonin, A.; Barth, W.; Heymach, F.; Hollinger, R.; Vormann, H.; Yakushev, A.

    2016-02-01

    In this contribution, the concept of production of intense proton beams using molecular heavy ion beams from an ion source is described, as well as the indisputable advantages of this technique for operation of the GSI linear accelerator. The results of experimental investigations, including mass-spectra analysis and beam emittance measurements, with different ion beams (CH3+,C2H4+,C3H7+) using various gaseous and liquid substances (methane, ethane, propane, isobutane, and iodoethane) at the ion source are summarized. Further steps to improve the ion source and injector performance with molecular beams are depicted.

  3. Production of high current proton beams using complex H-rich molecules at GSI.

    PubMed

    Adonin, A; Barth, W; Heymach, F; Hollinger, R; Vormann, H; Yakushev, A

    2016-02-01

    In this contribution, the concept of production of intense proton beams using molecular heavy ion beams from an ion source is described, as well as the indisputable advantages of this technique for operation of the GSI linear accelerator. The results of experimental investigations, including mass-spectra analysis and beam emittance measurements, with different ion beams (CH3(+),C2H4(+),C3H7(+)) using various gaseous and liquid substances (methane, ethane, propane, isobutane, and iodoethane) at the ion source are summarized. Further steps to improve the ion source and injector performance with molecular beams are depicted. PMID:26932072

  4. Ion-beam-induced magnetic and structural phase transformation of Ni-stabilized face-centered-cubic Fe films on Cu(100)

    SciTech Connect

    Gloss, Jonas; Shah Zaman, Sameena; Jonner, Jakub; Novotny, Zbynek; Schmid, Michael; Varga, Peter; Urbánek, Michal

    2013-12-23

    Metastable face-centered cubic (fcc) Fe/Cu(100) thin films are good candidates for ion-beam magnetic patterning due to their magnetic transformation upon ion-beam irradiation. However, pure fcc Fe films undergo spontaneous transformation when their thickness exceeds 10 ML. This limit can be extended to approximately 22 ML by deposition of Fe at increased CO background pressures. We show that much thicker films can be grown by alloying with Ni for stabilizing the fcc γ phase. The amount of Ni necessary to stabilize nonmagnetic, transformable fcc Fe films in dependence on the residual background pressure during the deposition is determined and a phase diagram revealing the transformable region is presented.

  5. Calculation and Verification of a Planar Pencil Beam Kernel Through the Hankel Transform of Measured OARs for a Radiosurgery System with Cones

    SciTech Connect

    Vargas Verdesoto, Milton X.; Alvarez Romero, Jose T.

    2010-12-07

    A planar multienergetic pencil beam kernel with rotational symmetry is calculated for a stereotactic radiosurgery system, SRS, BrainLAB with cones, employing the deconvolution method of the off axis ratio profile, OAR, corresponding to the cone of 35 mm in diameter for a 6 MV photon beam produced by a linear accelerator Varian 2100 C/D. Before the deconvolution, the experimental OAR is corrected for beam divergence and variations of the spectral fluence {Phi}, using a boundary function BF. The function BF and the fluence {Phi} are transformed to the conjugate space with the zero order Hankel function, which is the appropriate transform due to the radial symmetry of the circular beams generated by the cones. The kernel in the conjugate space is obtained as the ratio of the transform of BF to the transform of {Phi}, therefore the kernel in the real space is calculated as the inverse transform of the kernel in the conjugate space. To validate the kernel in the real space, it is convolved with the fluence of the cones of 7.5, 12.5, 15, 17.5, 20, 22.5, 25, 30 and 35 mm in diameter. The comparison of the OARs calculated and measured shows a maximum difference of 4.5% in the zones of high gradient of dose, and a difference less than 2% in the regions of low gradient of dose. Finally, the expanded uncertainty of the kernel is estimated and reported.

  6. Calculation and Verification of a Planar Pencil Beam Kernel Through the Hankel Transform of Measured OARs for a Radiosurgery System with Cones

    NASA Astrophysics Data System (ADS)

    Verdesoto, Milton X. Vargas; Romero, José T. Alvarez

    2010-12-01

    A planar multienergetic pencil beam kernel with rotational symmetry is calculated for a stereotactic radiosurgery system, SRS, BrainLAB™ with cones, employing the deconvolution method of the off axis ratio profile, OAR, corresponding to the cone of 35 mm in diameter for a 6 MV photon beam produced by a linear accelerator Varian 2100 C/D. Before the deconvolution, the experimental OAR is corrected for beam divergence and variations of the spectral fluence Φ, using a boundary function BF. The function BF and the fluence Φ are transformed to the conjugate space with the zero order Hankel function, which is the appropriate transform due to the radial symmetry of the circular beams generated by the cones. The kernel in the conjugate space is obtained as the ratio of the transform of BF to the transform of Φ, therefore the kernel in the real space is calculated as the inverse transform of the kernel in the conjugate space. To validate the kernel in the real space, it is convolved with the fluence of the cones of 7.5, 12.5, 15, 17.5, 20, 22.5, 25, 30 and 35 mm in diameter. The comparison of the OARs calculated and measured shows a maximum difference of 4.5% in the zones of high gradient of dose, and a difference less than 2% in the regions of low gradient of dose. Finally, the expanded uncertainty of the kernel is estimated and reported.

  7. Simulation of electrostatic turbulence in the plasma sheet boundary layer with electron currents and bean-shaped ion beams

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Frank, L. A.; Huang, C. Y.

    1988-01-01

    Plasma data from ISEE-1 show the presence of electron currents as well as energetic ion beams in the plasma sheet boundary layer. Broadband electrostatic noise and low-frequency electromagnetic bursts are detected in the plasma sheet boundary layer, especially in the presence of strong ion flows, currents, and steep spacial gradients in the fluxes of few-keV electrons and ions. Particle simulations have been performed to investigate electrostatic turbulence driven by a cold electron beam and/or ion beams with a bean-shaped velocity distribution. The simulation results show that the counterstreaming ion beams as well as the counterstreaming of the cold electron beam and the ion beam excite ion acoustic waves with a given Doppler-shifted real frequency. However, the effect of the bean-shaped ion velocity distributions reduces the growth rates of ion acoustic instability. The simulation results also show that the slowing down of the ion bean is larger at the larger perpendicular velocity. The wave spectra of the electric fields at some points of the simulations show turbulence generated by growing waves.

  8. Interface kinetics in phase-field models: Isothermal transformations in binary alloys and step dynamics in molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Boussinot, G.; Brener, Efim A.

    2013-08-01

    We present a unified description of interface kinetic effects in phase-field models for isothermal transformations in binary alloys and steps dynamics in molecular-beam-epitaxy. The phase-field equations of motion incorporate a kinetic cross-coupling between the phase field and the concentration field. This cross-coupling generalizes the phenomenology of kinetic effects and was omitted until recently in classical phase-field models. We derive general expressions (independent of the details of the phase-field model) for the kinetic coefficients within the corresponding macroscopic approach using a physically motivated reduction procedure. The latter is equivalent to the so-called thin-interface limit but is technically simpler. It involves the calculation of the effective dissipation that can be ascribed to the interface in the phase-field model. We discuss in detail the possibility of a nonpositive definite matrix of kinetic coefficients, i.e., a negative effective interface dissipation, although being in the range of stability of the underlying phase-field model. Numerically we study the step-bunching instability in molecular-beam-epitaxy due to the Ehrlich-Schwoebel effect, present in our model due to the cross-coupling. Using the reduction procedure we compare the results of the phase-field simulations with the analytical predictions of the macroscopic approach.

  9. Interface kinetics in phase-field models: isothermal transformations in binary alloys and step dynamics in molecular-beam epitaxy.

    PubMed

    Boussinot, G; Brener, Efim A

    2013-08-01

    We present a unified description of interface kinetic effects in phase-field models for isothermal transformations in binary alloys and steps dynamics in molecular-beam-epitaxy. The phase-field equations of motion incorporate a kinetic cross-coupling between the phase field and the concentration field. This cross-coupling generalizes the phenomenology of kinetic effects and was omitted until recently in classical phase-field models. We derive general expressions (independent of the details of the phase-field model) for the kinetic coefficients within the corresponding macroscopic approach using a physically motivated reduction procedure. The latter is equivalent to the so-called thin-interface limit but is technically simpler. It involves the calculation of the effective dissipation that can be ascribed to the interface in the phase-field model. We discuss in detail the possibility of a nonpositive definite matrix of kinetic coefficients, i.e., a negative effective interface dissipation, although being in the range of stability of the underlying phase-field model. Numerically we study the step-bunching instability in molecular-beam-epitaxy due to the Ehrlich-Schwoebel effect, present in our model due to the cross-coupling. Using the reduction procedure we compare the results of the phase-field simulations with the analytical predictions of the macroscopic approach. PMID:24032848

  10. High energy, high current neutral beam injector operation with single stage and two-stage multi-aperture extraction systems

    NASA Astrophysics Data System (ADS)

    Becherer, R.; Desmons, M.; Fumelli, M.; Raimbault, P.; Valckx, F. P. G.

    1982-12-01

    Neutral beam development for JET injections at FAR laboratory has led to the study of properties of a single stage (triode) and a two-stage (tetrode) multi-aperture extraction system at ion beam powers exceeding the megawatt level and up to 80 keV beam energy. The results of the experimental measurements and of a numerical study of the beam optical qualities and grid power loadings of these systems are presented. Grid power loading levels of less than 1% of the high-voltage drain power were measured in both the triode and the tetrode accelerators. This would allow long pulse operation (10 s with water-cooling) as required for JET. The beam divergence angle (α ≅ 0.7°) and the transmission characteristics were almostidentical. At the same energy, higher current densities, at optimum perveance, were obtained with the triode at a lower electric field stress on the high-voltage gap. The triode offers the additional advantage of being simpler from the mechanical and electrical points of view. Operation of the injection line with an electrostatic beam dump associated with a grounded source is also demonstrated for a 25 ion beam up to 60 keV.

  11. Genetic Transformation of Watermelon with Pumpkin DNA by Low Energy Ion Beam-Mediated Introduction

    NASA Astrophysics Data System (ADS)

    Wang, Hao-bo; Gao, Xiu-wu; Guo, Jin-hua; Huang, Qun-ce; Yu, Zeng-liang

    2002-12-01

    The No.601 watermelon (citrullus lanatus) seeds were treated with 25 keV N+ implantation at the dosage of 7.8 × 1016 ions/cm2. After treatment, watermelon seeds were incubated with 380 μg/μl pumpkin (Cucubita, maxima Duch) DNA solution at 35 °C for 5 hours. By two-generations of selection and resistance screening at seedling stage, one transformed material was selected out, whose rind color is similar to that of the donor pumpkin and whose size of seeds is between that of the donor and the receptor. Using AFLP (amplified fragment length polymorphism) technique, two polymorphic DNA fragments were amplified. This primarily testified that the donor DNA fragments/gene were introduced into the receptor cell and integrated into the genomic DNA of the receptor.

  12. Laser and electrical current induced phase transformation of In2Se3 semiconductor thin film on Si(111)

    NASA Astrophysics Data System (ADS)

    Lu, Chih-Yuan; Shamberger, Patrick J.; Yitamben, Esmeralda N.; Beck, Kenneth M.; Joly, Alan G.; Olmstead, Marjorie A.; Ohuchi, Fumio S.

    2008-10-01

    Phase transformation of thin film (˜30 nm)In2Se3/Si(111) (amorphous→crystalline) was performed by resistive annealing and the reverse transformation (crystalline→amorphous) was performed by nanosecond laser annealing. As an intrinsic-vacancy, binary chalcogenide semiconductor, In2Se3 is of interest for non-volatile phase-change memory. Amorphous In x Se y was deposited at room temperature on Si(111) after pre-deposition of a crystalline In2Se3 buffer layer (0.64 nm). Upon resistive annealing to 380°C, the film was transformed into a γ-In2Se3 single crystal with its {0001} planes parallel to the Si(111) substrate and (11bar{2}0) parallel to Si (1bar{1}0) , as evidenced by scanning tunneling microscopy, low energy electron diffraction, and X-ray diffraction. Laser annealing with 20-ns pulses (0.1 millijoules/pulse, fluence≤50 mJ/cm2) re-amorphized the region exposed to the laser beam, as observed with photoemission electron microscopy (PEEM). The amorphous phase in PEEM appears dark, likely due to abundant defect levels inhibiting electron emission from the amorphous In x Se y film.

  13. Ion beam annealing during high current density implants of phosphorus into silicon

    SciTech Connect

    Cannavo, S.; La Ferla, A.; Rimini, E.; Ferla, G.; Gandolfi, L.

    1986-06-15

    The damage left by high current densityapprox.10 ..mu..A/cm/sup 2/ implants of 120-keV P/sup +/ into 4-in. (500-..mu..m-thick) and 5-in. (600-..mu..m-thick) Si wafers of <100> orientation has been measured by 2.0-MeV He backscattering in combination with the channeling effect technique. The fluences ranged between 1 and 7.5 x 10/sup 15//cm/sup 2/. The amount of disorder is highest at 1 x 10/sup 15//cm/sup 2/ and then decreases with fluence. The annealing of the amorphous layer takes place by the movement of two and one amorphous--single crystal interfaces for the 500- and 600-..mu..m-thick wafers, respectively. The experimental data are compared with a beam annealing model based on the temperature-rise profile, the amount of point defects generated by the ion in the collision cascade volume, and the assumption of a regrowth process governed by an activation energy of 0.25 eV.

  14. Overview of the current spectroscopy effort on the Livermore electron beam ion traps

    SciTech Connect

    Beiersdorfer, P.; Lopez-Urrutia, J.C.; Brown, G.

    1995-06-29

    An overview is given of the current spectroscopic effort on the Livermore electron beam ion trap facilities. The effort focuses on four aspects: spectral line position, line intensity, temporal evolution, and line shape. Examples of line position measurements include studies of the K-shell transitions in heliumlike Kr{sup 34+} and the 2s-2p intrashell transitions in lithiumlike Th{sup 87+} and U{sup 89+}, which provide benchmark values for testing the theory of relativistic and quantum electrodynamical contributions in high-Z ions. Examples of line intensity measurements are provided by measurements of the electron-impact excitation and dielectronic recombination cross sections of heliumlike transition-metal ions Ti{sup 20+} through CO{sup 25+}. A discussion of radiative lifetime measurements of metastable levels in heliumlike ions is given to illustrate the time-resolved spectroscopy techniques in the microsecond range. The authors also present a measurement of the spectral lineshape that illustrates the very low ion temperatures that can be achieved in an EBIT.

  15. Experimental estimating deflection of a simple beam bridge model using grating eddy current sensors.

    PubMed

    Lü, Chunfeng; Liu, Weiwen; Zhang, Yongjie; Zhao, Hui

    2012-01-01

    A novel three-point method using a grating eddy current absolute position sensor (GECS) for bridge deflection estimation is proposed in this paper. Real spatial positions of the measuring points along the span axis are directly used as relative reference points of each other rather than using any other auxiliary static reference points for measuring devices in a conventional method. Every three adjacent measuring points are defined as a measuring unit and a straight connecting bar with a GECS fixed on the center section of it links the two endpoints. In each measuring unit, the displacement of the mid-measuring point relative to the connecting bar measured by the GECS is defined as the relative deflection. Absolute deflections of each measuring point can be calculated from the relative deflections of all the measuring units directly without any correcting approaches. Principles of the three-point method and displacement measurement of the GECS are introduced in detail. Both static and dynamic experiments have been carried out on a simple beam bridge model, which demonstrate that the three-point deflection estimation method using the GECS is effective and offers a reliable way for bridge deflection estimation, especially for long-term monitoring. PMID:23112583

  16. Ion beam annealing during high current density implants of phosphorus into silicon

    NASA Astrophysics Data System (ADS)

    Cannavó, S.; La Ferla, A.; Rimini, E.; Ferla, G.; Gandolfi, L.

    1986-06-01

    The damage left by high current density˜10 μA/cm2 implants of 120-keV P+ into 4-in. (500-μm-thick) and 5-in. (600-μm-thick) Si wafers of <100> orientation has been measured by 2.0-MeV He backscattering in combination with the channeling effect technique. The fluences ranged between 1 and 7.5×1015/cm2. The amount of disorder is highest at 1×1015/cm2 and then decreases with fluence. The annealing of the amorphous layer takes place by the movement of two and one amorphous-single crystal interfaces for the 500- and 600-μm-thick wafers, respectively. The experimental data are compared with a beam annealing model based on the temperature-rise profile, the amount of point defects generated by the ion in the collision cascade volume, and the assumption of a regrowth process governed by an activation energy of 0.25 eV.

  17. Improved wear resistance of Al-15Si alloy with a high current pulsed electron beam treatment

    NASA Astrophysics Data System (ADS)

    Hao, Y.; Gao, B.; Tu, G. F.; Li, S. W.; Dong, C.; Zhang, Z. G.

    2011-07-01

    A hypereutectic Al-15Si alloy (Si 15 wt.%, Al balance) was irradiated by high current pulsed electron beam (HCPEB). The HCPEB treatment causes ultra-rapid heating, melting and cooling at the top surface layer. As a result, the special "halo" microstructure centering on the primary Si phase is formed on the surface due to interdiffusion of Al and Si elements. The composition of the "halo" microstructure is distributed continuously from the center to the edge of the "halo". Compared to an untreated matrix, the remelted layer underneath the surface presents single contrast because of the compositional homogeneity after HCPEB treatment. The thickness of the remelted layer increases slightly from 4.4 μm (5 pulses) to 5.6 μm (25 pulses). HCPEB treatment broadens and shifts the diffraction peaks of Al and Si. The lattice parameters of Al decreases due to the formation of a supersaturated solid solution of Al in the melted layer. Through analysis of Raman spectra and transmission electron microscopy (TEM), the amorphous Si (a-Si) and nanocrystalline Si are formed in the near-surface region under multiple bombardments of HCPEB. The relative wear resistance of a 15-pulse sample is effectively improved by a factor of 9, which can be attributed to the formation of metastable structures.

  18. Radiation response of multi-quantum well solar cells: Electron-beam-induced current analysis

    SciTech Connect

    Maximenko, S. I. Scheiman, D. A.; Jenkins, P. P.; Walters, R. J.; Lumb, M. P.; Hoheisel, R.; Gonzalez, M.; Messenger, S. R.; Tibbits, T. N. D.; Imaizumi, M.; Ohshima, T.; Sato, S. I.

    2015-12-28

    Solar cells utilizing multi-quantum well (MQW) structures are considered promising candidate materials for space applications. An open question is how well these structures can resist the impact of particle irradiation. The aim of this work is to provide feedback about the radiation response of In{sub 0.01}Ga{sub 0.99}As solar cells grown on Ge with MQWs incorporated within the i-region of the device. In particular, the local electronic transport properties of the MQW i-regions of solar cells subjected to electron and proton irradiation were evaluated experimentally using the electron beam induced current (EBIC) technique. The change in carrier collection distribution across the MQW i-region was analyzed using a 2D EBIC diffusion model in conjunction with numerical modeling of the electrical field distribution. Both experimental and simulated findings show carrier removal and type conversion from n- to p-type in MQW i-region at a displacement damage dose as low as ∼6.06–9.88 × 10{sup 9} MeV/g. This leads to a redistribution of the electric field and significant degradation in charge carrier collection.

  19. Pressure and current balance conditions during electron beam injections from spacecraft

    NASA Technical Reports Server (NTRS)

    Hwang, K. S.; Singh, Nagendra

    1990-01-01

    Electrostatic charging level of a conducting surface in response to injections of electron beams into space plasma is investigated by means of one-dimensional Vlasov code. Injections of Maxwellian beams into a vacuum shows that the surface can charge up to an electric potential phi sub s greater than W sub b, where W sub b is the average electron beam energy. Since Maxwellian beams have extended trails with electrons having energies greater than W sub b, it is difficult to quantify the charging level in terms of the energies of the injected electrons. In order to quantitatively understand the charging in excess of W sub b, simulations were carried out for water-bag types of beam with velocity distribution functions described by f(V) = A for V sub min approx. less than V approx. less than V sub max and f(V) = O otherwise, where A is a constant making the normalized beam density unity. It is found that V sub max does not directly determine the charging level. The pressure distribution in the electron sheath determines the electric field distribution near the surface. The electric field in turn determines the electrostatic potential of the vehicle. The pressure distribution is determined by the beam parameters such as the average beam velocity and the velocity spread of the beam.

  20. Effect of external magnetic field on critical current for the onset of virtual cathode oscillations in relativistic electron beams

    NASA Astrophysics Data System (ADS)

    Hramov, Alexander; Koronovskii, Alexey; Morozov, Mikhail; Mushtakov, Alexander

    2008-02-01

    In this Letter we research the space charge limiting current value at which the oscillating virtual cathode is formed in the relativistic electron beam as a function of the external magnetic field guiding the beam electrons. It is shown that the space charge limiting (critical) current decreases with growth of the external magnetic field, and that there is an optimal induction value of the magnetic field at which the critical current for the onset of virtual cathode oscillations in the electron beam is minimum. For the strong external magnetic field the space charge limiting current corresponds to the analytical relation derived under the assumption that the motion of the electron beam is one-dimensional [D.J. Sullivan, J.E. Walsh, E. Coutsias, in: V.L. Granatstein, I. Alexeff (Eds.), Virtual Cathode Oscillator (Vircator) Theory, in: High Power Microwave Sources, vol. 13, Artech House Microwave Library, 1987, Chapter 13]. Such behavior is explained by the characteristic features of the dynamics of electron space charge in the longitudinal and radial directions in the drift space at the different external magnetic fields.

  1. Clinical utility of dental cone-beam computed tomography: current perspectives

    PubMed Central

    Jaju, Prashant P; Jaju, Sushma P

    2014-01-01

    Panoramic radiography and computed tomography were the pillars of maxillofacial diagnosis. With the advent of cone-beam computed tomography, dental practice has seen a paradigm shift. This review article highlights the potential applications of cone-beam computed tomography in the fields of dental implantology and forensic dentistry, and its limitations in maxillofacial diagnosis. PMID:24729729

  2. Beam charge and current neutralization of high-charge-state heavy ions

    SciTech Connect

    Logan, B.G.; Callahan, D.A.

    1997-10-29

    High-charge-state heavy-ions may reduce the accelerator voltage and cost of heavy-ion inertial fusion drivers, if ways can be found to neutralize the space charge of the highly charged beam ions as they are focused to a target in a fusion chamber. Using 2-D Particle-In- Cell simulations, we have evaluated the effectiveness of two different methods of beam neutralization: (1) by redistribution of beam charge in a larger diameter, preformed plasma in the chamber, and (2), by introducing a cold-electron-emitting source within the beam channel at the beam entrance into the chamber. We find the latter method to be much more effective for high-charge-state ions.

  3. Ion beam induced cubic to monoclinic phase transformation of nanocrystalline yttria

    NASA Astrophysics Data System (ADS)

    Shivaramu, N. J.; Lakshminarasappa, B. N.; Nagabhushana, K. R.; Singh, Fouran

    2016-07-01

    Sol gel derived nanocrystalline yttria pellets are irradiated with 120 MeV Ag9+ ions for fluence in the range 1 × 1012-3 × 1013 ions cm-2. Pristine and irradiated samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. XRD pattern of pristine Y2O3 nanocrystal reveal cubic structure. A new XRD peak at 30.36° is observed in pellet irradiated with 1 × 1013 ions cm-2. The peak at 30.36° is corresponding to (4 0 2 bar) plane of monoclinic phase. The diffraction intensity of (4 0 2 bar) plane increases with Ag9+ ion fluence. Raman spectrum of pristine pellet show bands corresponding to cubic phase. And, ion irradiated sample show new peaks at 410, 514 and 641 cm-1 corresponding monoclinic phase. HR-TEM and SAED pattern of ion irradiated sample confirmed the presence of monoclinic phase. Hence, it is confirmed that, 120 MeV Ag9+ ions induce phase transformation in nanocrystalline Y2O3.

  4. Current status and perspectives in atomic force microscopy-based identification of cellular transformation

    PubMed Central

    Dong, Chenbo; Hu, Xiao; Dinu, Cerasela Zoica

    2016-01-01

    Understanding the complex interplay between cells and their biomechanics and how the interplay is influenced by the extracellular microenvironment, as well as how the transforming potential of a tissue from a benign to a cancerous one is related to the dynamics of both the cell and its surroundings, holds promise for the development of targeted translational therapies. This review provides a comprehensive overview of atomic force microscopy-based technology and its applications for identification of cellular progression to a cancerous phenotype. The review also offers insights into the advancements that are required for the next user-controlled tool to allow for the identification of early cell transformation and thus potentially lead to improved therapeutic outcomes. PMID:27274238

  5. Transportation of high-current ion and electron beams in the accelerator drift gap in the presence of an additional electron background

    NASA Astrophysics Data System (ADS)

    Karas', V. I.; Kornilov, E. A.; Manuilenko, O. V.; Tarakanov, V. P.; Fedorovskaya, O. V.

    2015-12-01

    The dynamics of a high-current ion beam propagating in the drift gap of a linear induction accelerator with collective focusing is studied using 3D numerical simulations in the framework of the full system of the Vlasov-Maxwell equations (code KARAT). The ion beam is neutralized by a comoving electron beam in the current density and, partially, in space charge, since the velocities of electrons and ions differ substantially. The dynamics of the high-current ion beam is investigated for different versions of additional neutralization of its space charge. It is established that, for a given configuration of the magnetic field and in the presence of a specially programmed injection of additional electrons from the boundary opposite to the ion injection boundary, the angular divergence of the ion beam almost vanishes, whereas the current of the ion beam at the exit from the accelerator drift gap changes insignificantly and the beam remains almost monoenergetic.

  6. Transportation of high-current ion and electron beams in the accelerator drift gap in the presence of an additional electron background

    SciTech Connect

    Karas’, V. I. Kornilov, E. A.; Manuilenko, O. V.; Tarakanov, V. P.; Fedorovskaya, O. V.

    2015-12-15

    The dynamics of a high-current ion beam propagating in the drift gap of a linear induction accelerator with collective focusing is studied using 3D numerical simulations in the framework of the full system of the Vlasov–Maxwell equations (code KARAT). The ion beam is neutralized by a comoving electron beam in the current density and, partially, in space charge, since the velocities of electrons and ions differ substantially. The dynamics of the high-current ion beam is investigated for different versions of additional neutralization of its space charge. It is established that, for a given configuration of the magnetic field and in the presence of a specially programmed injection of additional electrons from the boundary opposite to the ion injection boundary, the angular divergence of the ion beam almost vanishes, whereas the current of the ion beam at the exit from the accelerator drift gap changes insignificantly and the beam remains almost monoenergetic.

  7. Novel signal inversion of laser beam induced current for femtosecond-laser-drilling-induced junction on vacancy-doped p-type HgCdTe

    SciTech Connect

    Qiu, W. C.; Wang, R.; Xu, Z. J.; Jiang, T.; Cheng, X. A.

    2014-05-28

    In this paper, experimental results of temperature-dependent signal inversion of laser beam induced current (LBIC) for femtosecond-laser-drilling-induced junction on vacancy-doped p-type HgCdTe are reported. LBIC characterization shows that the traps induced by femtosecond laser drilling are sensitive to temperature. Theoretical models for trap-related p-n junction transformation are proposed and demonstrated using numerical simulations. The simulations are in good agreement with the experimental results. The effects of traps and mixed conduction are possibly the main reasons that result in the novel signal inversion of LBIC microscope at room temperature. The research results provide a theoretical guide for practical applications of large-scale array HgCdTe infrared photovoltaic detectors formed by femtosecond laser drilling, which may act as a potential new method for fabricating HgCdTe photodiodes.

  8. SUPPLEMENTARY COMPARISON: Final report EURAMET.EM-S30 on EURAMET Project 1081: Supplementary comparison of measurements of current transformers

    NASA Astrophysics Data System (ADS)

    Dimitrov, Emil; Kumanova, Ginka; Styblíková, Renata; Draxler, Karel; Dierikx, Erik

    2010-01-01

    The supplementary comparison was carried out between CMI, Czech Republic and BIM, NCM Bulgaria in the field of current transformer ratio measurements. The current errors and phase displacement of the traveling standards, current transformers: Tettex 4720, CLA 2.2, CLA 2.2, CLA 3.2, CLB 10, I 523 were determined at 50 Hz, 5 VA burden at unity power factor at ratios: primary (4000, 2000, 1000, 500, 100, 5, 1 and 0.5) A/secondary 5 A. Both participants used their own standard measurement method. The obtained results show good agreement for all of the current ratio error measurements (except for the measurements at 2 kA) and for the current phase displacement measurements (the agreement on several measurement points is marginal). The aim of the comparison was to demonstrate the improvement and extension of the calibration and measurement capabilities (CMCs) of BIM in this working field and to support the improved CMCs in Appendix C of the CIPM Mutual Recognition Arrangement (MRA). Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

  9. Surface modification of Al-20Si alloy by high current pulsed electron beam

    NASA Astrophysics Data System (ADS)

    Hao, Y.; Gao, B.; Tu, G. F.; Li, S. W.; Hao, S. Z.; Dong, C.

    2011-02-01

    Hypereutectic Al-20Si (Si 20 wt.%, Al balance)alloy surface was treated with high current pulsed electron beam (HCPEB) under different pulse numbers. The results indicate that HCPEB irradiation induces the formation of metastable structures on the treated surface. The coarse primary Si particle melts, producing a "halo" microstructure with primary Si as the center on the melted surface. A supersaturated solid solution of Al is formed in the melted layer caused by Si atoms dissolving into the Al matrix. Cross-section structure analysis shows that a 4 μm remelted layer is formed underneath the top surface of the HCEPB-treated sample. Compared with the matrix, the Al and Si elements in the remelted layer are distributed uniformly. In addition, the grains of the Al-20Si alloy surface are refined after HCPEB treatment, as shown by TEM observation. Nano-silicon particles are dispersed on the surface of remelted layer. Polygonal subgrains, approximately 50-100 nm in size, are formed in the Al matrix. The hardness test results show that the microhardness of the α(Al) and eutectic structure is increased with increasing pulse number. The hardness of the "halo" microstructure presents a gradient change after 15 pulse treatment due to the diffusion of Si atoms. Furthermore, hardness tests of the cross-section at different depths show that the microhardness of the remelted layer is higher than that of the matrix. Therefore, HCPEB technology is a good surface modification method for enhancing the surface hardness of hypereutectic Al-20Si alloy.

  10. High current/high power beam experiments from the space station

    NASA Technical Reports Server (NTRS)

    Cohen, Herbert A.

    1986-01-01

    In this overview, on the possible uses of high power beams aboard the space station, the advantages of the space station as compared to previous space vehicles are considered along with the kind of intense beams that could be generated, the possible scientific uses of these beams and associated problems. This order was delibrately chosen to emphasize that the means, that is, the high power particle ejection devices, will lead towards the possible ends, scientific measurements in the Earth's upper atmosphere using large fluxes of energetic particles.

  11. Basis for low beam loss in the high-current APT linac

    SciTech Connect

    Wangler, T.P.; Gray, E.R.; Krawczyk, F.L.; Kurennoy, S.S.; Lawrence, G.P.; Ryne, R.D.; Crandall, K.R.

    1998-12-31

    The present evidence that the APT proton linac design will meet its goal of low beam loss operation. The conclusion has three main bases: (1) extrapolation from the understanding of the performance of the 800-MeV LANSCE proton linac at Los Alamos, (2) the theoretical understanding of the dominant halo-forming mechanism in the APT accelerator from physics models and multiparticle simulations, and (3) the conservative approach and key principles underlying the design of the APT linac, which are aimed at minimizing beam halo and providing large apertures to reduce beam loss to a very low value.

  12. Preliminary results concerning the simulation of beam profiles from extracted ion current distributions for mini-STRIKE

    NASA Astrophysics Data System (ADS)

    Agostinetti, P.; Giacomin, M.; Serianni, G.; Veltri, P.; Bonomo, F.; Schiesko, L.

    2016-02-01

    The Radio Frequency (RF) negative hydrogen ion source prototype has been chosen for the ITER neutral beam injectors due to its optimal performances and easier maintenance demonstrated at Max-Planck-Institut für Plasmaphysik, Garching in hydrogen and deuterium. One of the key information to better understand the operating behavior of the RF ion sources is the extracted negative ion current density distribution. This distribution—influenced by several factors like source geometry, particle drifts inside the source, cesium distribution, and layout of cesium ovens—is not straightforward to be evaluated. The main outcome of the present contribution is the development of a minimization method to estimate the extracted current distribution using the footprint of the beam recorded with mini-STRIKE (Short-Time Retractable Instrumented Kalorimeter). To accomplish this, a series of four computational models have been set up, where the output of a model is the input of the following one. These models compute the optics of the ion beam, evaluate the distribution of the heat deposited on the mini-STRIKE diagnostic calorimeter, and finally give an estimate of the temperature distribution on the back of mini-STRIKE. Several iterations with different extracted current profiles are necessary to give an estimate of the profile most compatible with the experimental data. A first test of the application of the method to the BAvarian Test Machine for Negative ions beam is given.

  13. Preliminary results concerning the simulation of beam profiles from extracted ion current distributions for mini-STRIKE.

    PubMed

    Agostinetti, P; Giacomin, M; Serianni, G; Veltri, P; Bonomo, F; Schiesko, L

    2016-02-01

    The Radio Frequency (RF) negative hydrogen ion source prototype has been chosen for the ITER neutral beam injectors due to its optimal performances and easier maintenance demonstrated at Max-Planck-Institut für Plasmaphysik, Garching in hydrogen and deuterium. One of the key information to better understand the operating behavior of the RF ion sources is the extracted negative ion current density distribution. This distribution-influenced by several factors like source geometry, particle drifts inside the source, cesium distribution, and layout of cesium ovens-is not straightforward to be evaluated. The main outcome of the present contribution is the development of a minimization method to estimate the extracted current distribution using the footprint of the beam recorded with mini-STRIKE (Short-Time Retractable Instrumented Kalorimeter). To accomplish this, a series of four computational models have been set up, where the output of a model is the input of the following one. These models compute the optics of the ion beam, evaluate the distribution of the heat deposited on the mini-STRIKE diagnostic calorimeter, and finally give an estimate of the temperature distribution on the back of mini-STRIKE. Several iterations with different extracted current profiles are necessary to give an estimate of the profile most compatible with the experimental data. A first test of the application of the method to the BAvarian Test Machine for Negative ions beam is given. PMID:26932085

  14. An inversion formula for the exponential Radon transform in spatial domain with variable focal-length fan-beam collimation geometry

    SciTech Connect

    Wen Junhai; Liang Zhengrong

    2006-03-15

    Inverting the exponential Radon transform has a potential use for SPECT (single photon emission computed tomography) imaging in cases where a uniform attenuation can be approximated, such as in brain and abdominal imaging. Tretiak and Metz derived in the frequency domain an explicit inversion formula for the exponential Radon transform in two dimensions for parallel-beam collimator geometry. Progress has been made to extend the inversion formula for fan-beam and varying focal-length fan-beam (VFF) collimator geometries. These previous fan-beam and VFF inversion formulas require a spatially variant filtering operation, which complicates the implementation and imposes a heavy computing burden. In this paper, we present an explicit inversion formula, in which a spatially invariant filter is involved. The formula is derived and implemented in the spatial domain for VFF geometry (where parallel-beam and fan-beam geometries are two special cases). Phantom simulations mimicking SPECT studies demonstrate its accuracy in reconstructing the phantom images and efficiency in computation for the considered collimator geometries.

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

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

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

  16. Investigations of Beam Dynamics Issues at Current and Future Hadron Accelerators

    SciTech Connect

    Ellison, James; Lau, Stephen; Heinemann, Klaus; Bizzozero, David

    2015-03-12

    Final Report Abstract for DE-FG02-99ER4110, May 15, 2011- October 15, 2014 There is a synergy between the fields of Beam Dynamics (BD) in modern particle accelerators and Applied Mathematics (AMa). We have formulated significant problems in BD and have developed and applied tools within the contexts of dynamical systems, topological methods, numerical analysis and scientific computing, probability and stochastic processes, and mathematical statistics. We summarize the three main areas of our AMa work since 2011. First, we continued our study of Vlasov-Maxwell systems. Previously, we developed a state of the art algorithm and code (VM3@A) to calculate coherent synchrotron radiation in single pass systems. In this cycle we carefully analyzed the major expense, namely the integral-over-history (IOH), and developed two approaches to speed up integration. The first strategy uses a representation of the Bessel function J0 in terms of exponentials. The second relies on “local sequences” developed recently for radiation boundary conditions, which are used to reduce computational domains. Although motivated by practicality, both strategies involve interesting and rather deep analysis and approximation theory. As an alternative to VM3@A, we are integrating Maxwell’s equations by a time-stepping method, bypass- ing the IOH, using a Discontinuous Galerkin (DG) method. DG is a generalization of Finite Element and Finite Volume methods. It is spectrally convergent, unlike the commonly used Finite Difference methods, and can handle complicated vacuum chamber geometries. We have applied this in several contexts and have obtained very nice results including an explanation of an experiment at the Canadian Light Source, where the geometry is quite complex. Second, we continued our study of spin dynamics in storage rings. There is much current and proposed activity where spin polarized beams are being used in testing the Standard Model and its modifications. Our work has focused

  17. Current limiting behavior in three-phase transformer-type SFCLs using an iron core according to variety of fault

    NASA Astrophysics Data System (ADS)

    Cho, Yong-Sun; Jung, Byung-Ik; Ha, Kyoung-Hun; Choi, Soo-Geun; Park, Hyoung-Min; Choi, Hyo-Sang

    To apply the superconducting fault current limiter (SFCL) to the power system, the reliability of the fault-current-limiting operation must be ensured in diverse fault conditions. The SFCL must also be linked to the operation of the high-speed recloser in the power system. In this study, a three-phase transformer-type SFCL, which has a neutral line to improve the simultaneous quench characteristics of superconducting elements, was manufactured to analyze the fault-current-limiting characteristic according to the single, double, and triple line-to-ground faults. The transformer-type SFCL, wherein three-phase windings are connected to one iron core, reduced the burden on the superconducting element as the superconducting element on the sound phase was also quenched in the case of the single line-to-ground fault. In the case of double or triple line-to-ground faults, the flux from the faulted phase winding was interlinked with other faulted or sound phase windings, and the fault-current-limiting rate decreased because the windings of three phases were inductively connected by one iron core.

  18. Improved measurement of neutral current coherent $\\pi^0$ production on carbon in a few-GeV neutrino beam

    SciTech Connect

    Kurimoto, Y.; Alcaraz-Aunion, J.L.; Brice, S.J.; Bugel, L.; Catala-Perez, J.; Cheng, G.; Conrad, J.M.; Djurcic, Z.; Dore, U.; Finley, D.A.; Franke, A.J.; /Columbia U. /INFN, Rome

    2010-05-01

    The SciBooNE Collaboration reports a measurement of neutral current coherent neutral pion production on carbon by a muon neutrino beam with average energy 0.8 GeV. The separation of coherent from inclusive neutral pion production has been improved by detecting recoil protons from resonant neutral pion production. We measure the ratio of the neutral current coherent neutral pion production to total charged current cross sections to be (1.16 +/- 0.24) x 10-2. The ratio of charged current coherent pion to neutral current coherent pion production is calculated to be 0.14+0.30 -0.28, using our published charged current coherent pion measurement.

  19. The coordinate transformation method for design of polarizers on HL-2A electron cyclotron resonance heating and current drive systems

    SciTech Connect

    Xia, D. H.; Huang, M.; Zhou, J.; Rao, J.; Zhuang, G.

    2013-10-15

    Polarizers are widely used to change the polarization of millimeter waves on the electron cyclotron resonance heating and current drive (ECRH and CD) systems. A new method based on the coordinate transformation and the Fourier expansion (the so-called C-method) has been developed for design of polarizers on the HL-2A ECRH and CD systems. This method transforms the grating problem to an eigenvalue problem, making it easy and clear to understand and solve. The comparison between the C-method, the integral method, and the low power test results is presented. It indicates that the C-method can be considered as a rigorous numerical method for the design of polarizers. Finally, two polarizers were designed based on the C-method which can be used together to achieve almost arbitrary polarization.

  20. Structural and phase transformations in zinc and brass wires under heating with high-density current pulse

    NASA Astrophysics Data System (ADS)

    Pervikov, A. V.

    2016-06-01

    The work is focused on revealing the mechanism of structure and phase transformations in the metal wires under heating with a high-density current pulse (the electric explosion of wires, EEWs). It has been demonstrated on the example of brass and zinc wires that the transition of a current pulse with the density of j ≈ 3.3 × 107 A/cm2 results in homogeneous heating of the crystalline structure of the metal/alloy. It has been determined that under heating with a pulse of high-density current pulse, the electric resistance of the liquid phases of zinc and brass decreases as the temperature increases. The results obtained allow for a conclusion that the presence of the particles of the condensed phase in the expanding products of EEW is the result of overheating instabilities in the liquid metal.

  1. INSTRUMENTS AND METHODS OF INVESTIGATION: Controlled ion-beam transformation of electrical, magnetic, and optical materials properties

    NASA Astrophysics Data System (ADS)

    Gurovich, B. A.; Dolgii, D. I.; Kuleshova, E. A.; Velikhov, E. P.; Ol'shanskii, E. D.; Domantovskii, A. G.; Aronzon, B. A.; Meilikhov, Evgenii Z.

    2001-01-01

    The key condition for radical progress in technology in the 21th century is the availability of a technique for the controlled production in a solid of 3D patterns incorporating regions of desired physical and chemical properties, with the possibility of downsizing pattern elements to the nanometer scale being a crucial requirement. In this paper, a method for changing the electrical, magnetic, optical and other key physical properties in a direct and deliberate manner by radically modifying the solid's atomic composition is proposed for the first time. The physical foundation of the new nonlithography technology is the observation — thoroughly investigated and well verified in our numerous experiments — that accelerated particle beams can be used to selectively remove atoms from thin films of di- or polyatomic compounds. It is shown, in particular, that by selectively removing atoms of a given sort, dielectrics can be transformed into metals or semiconductors, nonmagnetic materials into magnetic ones, and the optical and other properties of materials can be changed radically. The selective removal of atoms of a specified sort from a material is of great interest for future technologies, especially for those relevant to nanoelectronics and, more broadly, to the numerous 'nanoproblems' ahead in the third millennium.

  2. THE n-DISTRIBUTION OF ELECTRONS AND DOUBLE LAYERS IN THE ELECTRON-BEAM-RETURN-CURRENT SYSTEM OF SOLAR FLARES

    SciTech Connect

    Karlicky, Marian

    2012-05-01

    We investigate processes in the electron-beam-return-current system in the impulsive phase of solar flares to answer a question about the formation of the n-electron distribution detected in this phase of solar flares. An evolution of the electron-beam-return-current system with an initial local density depression is studied using a three-dimensional electromagnetic particle-in-cell model. In the system the strong double layer is formed. Its electric field potential increases with the electron beam flux. In this electric field potential, the electrons of background plasma are strongly accelerated and propagate in the return-current direction. The high-energy part of their distribution at the high-potential side of the strong double layer resembles that of the n-distribution. Thus, the detection of the n-distributions, where a form of the high-energy part of the distribution is the most important, can indicate the presence of strong double layers in solar flares. The similarity between processes in solar flare loops and those in the downward current region of the terrestrial aurora, where the double layers were observed by FAST satellite, supports this idea.

  3. Current-driven Langmuir oscillations and amplitude modulations—Another view on electron beam-plasma interaction

    NASA Astrophysics Data System (ADS)

    Sauer, K.; Sydora, R. D.

    2015-01-01

    origin of Langmuir amplitude modulations and harmonic waves observed in the solar wind and in planetary foreshock regions is investigated in beam plasmas where the saturation process of the beam instability is accompanied with the formation of a plateau distribution. This saturated state represents a current which is shown to drive homogeneous electric field oscillations at the plasma frequency. This simple mechanism has been ignored in most numerical studies based on Vlasov or particle-in-cell simulations because of the use of the Poisson equation which is not suitable to describe the mechanism of current drive in plasmas with immobile ions; instead, Ampere's law must be used. A simple fluid description of stable plateau plasmas, coupled with Ampere's law, is applied to illustrate the basic elements of current-driven Langmuir oscillations. If beam-generated Langmuir/electron-acoustic waves with frequencies above or below the plasma frequency are simultaneously present, beating of both wave modes leads to Langmuir amplitude modulations, thus providing an alternative to parametric decay. Furthermore, very important implications of our studies (presented separately) concern the electrostatic and electromagnetic second harmonic generation by nonlinear interaction of Langmuir oscillations with finite wave number modes which are driven by the plateau current as well.

  4. The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

    NASA Astrophysics Data System (ADS)

    Ivanov, Yuri; Tolkachev, Oleg; Petyukevich, Maria; Teresov, Anton; Ivanova, Olga; Ikonnikova, Irina; Polisadova, Valentina

    2016-01-01

    The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm2, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance.

  5. Proton Beam Therapy for Non-Small Cell Lung Cancer: Current Clinical Evidence and Future Directions

    PubMed Central

    Berman, Abigail T.; St. James, Sara; Rengan, Ramesh

    2015-01-01

    Lung cancer is the leading cancer cause of death in the United States. Radiotherapy is an essential component of the definitive treatment of early-stage and locally-advanced lung cancer, and the palliative treatment of metastatic lung cancer. Proton beam therapy (PBT), through its characteristic Bragg peak, has the potential to decrease the toxicity of radiotherapy, and, subsequently improve the therapeutic ratio. Herein, we provide a primer on the physics of proton beam therapy for lung cancer, present the existing data in early-stage and locally-advanced non-small cell lung cancer (NSCLC), as well as in special situations such as re-irradiation and post-operative radiation therapy. We then present the technical challenges, such as anatomic changes and motion management, and future directions for PBT in lung cancer, including pencil beam scanning. PMID:26147335

  6. Wavelet transform-based fault diagnosis and line selection method of small current grounding system

    NASA Astrophysics Data System (ADS)

    Yang, Ni; Zhang, Shuqing; Zhang, Liguo; Zhang, Kexin; Sun, Lingyun

    2008-12-01

    Small current grounding system is the system that the neutral point doesn't ground or grounds across the arc suppressing coils, which has been applied commonly in distribution system of many countries. As the grounding fault occurs, current is the one caused by capacity of circuit to ground only and it is rather small. The status of fault is complexity, e.g., the electromagnet interferes together with the amplified impact of zero-order loops to high-order singularity waves and various temporary variables. All these result in the lower ratio of the fault element signal to noise caused by zero-order current. In this paper, the position of signal singularity and the magnitude of the singularity degree are analyzed based on the variable focus character of wavelet, and the time fault occurs is then determined. The series db wavelet with close sustain is adopted, and the line selection is according to the zero-order voltage of the generatrix and the current of various outlet line. It is proved by the experiment that the fault circuit diagnosis method based on wavelet analysis to the character of temporary status of single-phase grounding fault plays an important role to a finer line selection.

  7. Studies of high-current relativistic electron beam interaction with gas and plasma in Novosibirsk

    NASA Astrophysics Data System (ADS)

    Sinitsky, S. L.; Arzhannikov, A. V.; Burdakov, A. V.

    2016-03-01

    This paper presents an overview of the studies on the interaction of a high-power relativistic electron beam (REB) with dense plasma confined in a long open magnetic trap. The main goal of this research is to achieve plasma parameters close to those required for thermonuclear fusion burning. The experimental studies were carried over the course of four decades on various devices: INAR, GOL, INAR-2, GOL-M, and GOL-3 (Budker Institute of Nuclear Physics) for a wide range of beam and plasma parameters.

  8. Collective acceleration of electrons and ions in a high current relativistic electron beam. Final report

    SciTech Connect

    Nation, J.A.

    1996-12-31

    The original purpose of this research was an investigation into the use of slow space charge waves on weakly relativistic electron beams for ion acceleration. The work had three main objectives namely, the development of a suitable ion injector, the growth and study of the properties of slow space charge waves on an electron beam, and a combination of the two components parts into a suitable proof of principle demonstration of the wave accelerator. This work focusses on the first two of these objectives.

  9. Numerical Modeling of Annular High-Current Relativistic Beam Forming in a Toroidal Chamber with a Magnet

    NASA Astrophysics Data System (ADS)

    Bogdanovich, B. Yu.; L'vov, E. I.; Nesterovich, A. V.; Sukhanova, L. A.; Khlestkov, Yu. A.

    2016-04-01

    A scheme of forming an annular high-current relativistic beam (HCRB) from a directly propagating HCRB in a diode with magnetic insulation and toroidal chamber with a constant magnet is described. The code KARAT is used to analyze numerically the HCRB dynamics. It is demonstrated that for a proper relationship of the system parameters the directly propagating HCRB is rolled up into a torus.

  10. First results and current development of SpIOMM: an imaging Fourier transform spectrometer for astronomy

    NASA Astrophysics Data System (ADS)

    Bernier, A.-P.; Grandmont, F.; Rochon, J.-F.; Charlebois, M.; Drissen, L.

    2006-06-01

    We present an overview of SpIOMM, an Imaging Fourier Transform Spectrometer (IFTS) for astronomy developed at University Laval in collaboration with ABB, INO and the Canadian Space Agency. SpIOMM, attached to the 1.6 meter (f/8) telescope at the Observatoire du mont Megantic in Quebec. It is a Michelson-type interferometer capable of obtaining the visible spectrum (from 350 nm to 900 nm) of every light source within its 12 arcminute circular field of view. This design will allow the correction of variable sky transmission. It consists of a dual output port and the total throughput is exploited by two CCDs used as detectors. We present the concept and design of this unique instrument. A metrology system combined with a dynamic alignment assures a good sampling and mirror alignment during the entire acquisition sequence. This particular servo control is explained and demonstrated and its capabilities and performance are discussed. We introduce the use of specific bandpass filters centered on the most important groups of emission lines which, when combined with spectral folding algorithms, allows us to reach high spectral resolution (R = 25 000, or 1 cm -1). Astronomical data collected by SpIOMM in 2004-2005 are also presented.

  11. Real space mapping of oxygen vacancy diffusion and electrochemical transformations by hysteretic current reversal curve measurements

    DOEpatents

    Kalinin, Sergei V.; Balke, Nina; Borisevich, Albina Y.; Jesse, Stephen; Maksymovych, Petro; Kim, Yunseok; Strelcov, Evgheni

    2014-06-10

    An excitation voltage biases an ionic conducting material sample over a nanoscale grid. The bias sweeps a modulated voltage with increasing maximal amplitudes. A current response is measured at grid locations. Current response reversal curves are mapped over maximal amplitudes of the bias cycles. Reversal curves are averaged over the grid for each bias cycle and mapped over maximal bias amplitudes for each bias cycle. Average reversal curve areas are mapped over maximal amplitudes of the bias cycles. Thresholds are determined for onset and ending of electrochemical activity. A predetermined number of bias sweeps may vary in frequency where each sweep has a constant number of cycles and reversal response curves may indicate ionic diffusion kinetics.

  12. Clinical evaluation of neutron beam therapy. Current results and prospects, 1983

    SciTech Connect

    Cohen, L.; Hendrickson, F.R.; Kurup, P.D.; Mansell, J.A.; Awschalom, M.; Rosenberg, I.; Ten Haken, R.K.

    1985-01-01

    Some 9000 patients throughout the world have been treated by some form of neutron beam therapy. These include patients with advanced nonresectable tumors in many different sites treated with a variety of neutron beam generators varying widely in beam energy. Protocols were largely nonrandomized and included both mixed beam studies (neutrons + photons) and neutrons alone in varying doses. In spite of wide variation in equipment, treatment technique, and philosophy, some consistent trends have been identified: (1) in general, the neutron results have been at least as good as those of the photon controls measured in terms of local control, although the incidence of significant side effects have been higher; (2) in none of the randomized studies conducted so far, largely comprising epidermoid carcinomas of the head and neck, has a clear survival advantage for neutrons over photon controls been demonstrated at a statistically significant level; (3) results with mixed beam studies have been uniformly equivocal, with marginally significant differences in favor of the experimental groups compared with the photon controls; (4) adenocarcinomas of the gastrointestinal tract (GI) tract, including tumors of the salivary gland, pancreas, stomach, and bowel, appear to be responsive to high linear energy transfer (LET) radiation; (5) nonepidermoid, radioresistant tumors (sarcoma of bone and soft tissue and melanoma) yield a consistantly high local control rate, with neutron irradiation strikingly superior to those reported with photon therapy; and (6) in the central nervous system, both normal tissues and tumors appear to be exceptionally sensitive to neutron irradiation, therapeutic ratios are small, and the prospect of cure remains remote. It is concluded that neutrons are efficacious for certain specific tumor types, but that essentially new study designs, based on nonrandomized matched case comparisons, will be required to prove the merit of the new modality.

  13. Study of a piezoelectric transformer-based DC/DC converter with a cooling system and current-doubler rectifier

    NASA Astrophysics Data System (ADS)

    Su, Yu-Hao; Liu, Yuan-Ping; Vasic, Dejan; Costa, Francois; Wu, Wen-Jong; Lee, Chuih-Kung

    2013-09-01

    The objective of this study was to increase the output current and power in a piezoelectric transformer (PT)-based DC/DC converter by using a cooling system. It is known that the output current of a PT is limited by temperature build-up because of losses, especially when driving at high vibration velocity. Although connecting different inductive circuits at the PT secondary terminal can increase the output current, the root cause of the temperature build-up problem has not yet been solved. This paper presents a study of a PT with cooling system in a DC/DC converter with a commonly used full-bridge rectifier and current-doubler rectifier. The advantages and disadvantages of the proposed technique were investigated. A theoretical-phenomenological model was developed to explain the relationship between the losses and the temperature rise. It will be shown that the vibration velocity as well as heat generation increases the losses. In our design, the maximum output current capacity can increase by 100% when the temperature of operation of the PT is kept below 55 ° C. The study comprises a theoretical part and experimental proof-of-concept demonstration of the proposed design method.

  14. Comparison of the quench and fault current limiting characteristics of the flux-coupling type SFCL with single and three-phase transformer

    NASA Astrophysics Data System (ADS)

    Jung, Byung Ik; Cho, Yong Sun; Park, Hyoung Min; Chung, Dong Chul; Choi, Hyo Sang

    2013-01-01

    The South Korean power grid has a network structure for the flexible operation of the system. The continuously increasing power demand necessitated the increase of power facilities, which decreased the impedance in the power system. As a result, the size of the fault current in the event of a system fault increased. As this increased fault current size is threatening the breaking capacity of the circuit breaker, the main protective device, a solution to this problem is needed. The superconducting fault current limiter (SFCL) has been designed to address this problem. SFCL supports the stable operation of the circuit breaker through its excellent fault-current-limiting operation [1-5]. In this paper, the quench and fault current limiting characteristics of the flux-coupling-type SFCL with one three-phase transformer were compared with those of the same SFCL type but with three single-phase transformers. In the case of the three-phase transformers, both the superconducting elements of the fault and sound phases were quenched, whereas in the case of the single-phase transformer, only that of the fault phase was quenched. For the fault current limiting rate, both cases showed similar rates for the single line-to-ground fault, but for the three-wire earth fault, the fault current limiting rate of the single-phase transformer was over 90% whereas that of the three-phase transformer was about 60%. It appears that when the three-phase transformer was used, the limiting rate decreased because the fluxes by the fault current of each phase were linked in one core. When the power loads of the superconducting elements were compared by fault type, the initial (half-cycle) load was great when the single-phase transformer was applied, whereas for the three-phase transformer, its power load was slightly lower at the initial stage but became greater after the half fault cycle.

  15. Comparisons of Monte Carlo calculations with absorbed dose determinations in flat materials using high-current, energetic electron beams

    NASA Astrophysics Data System (ADS)

    Cleland, Marshall R.; Galloway, Richard A.; Heiss, Arthur H.; Logar, John R.

    2007-08-01

    International standards and guidelines for calibrating high-dose dosimetry systems to be used in industrial radiation processing recommend that dose-rate effects on dosimeters be evaluated under conditions of use. This is important when the irradiation relies on high-current electron accelerators, which usually provide very high dose-rates. However, most dosimeter calibration facilities use low-intensity gamma radiation or low-current electron accelerators, which deliver comparatively low dose-rates. Because of issues of thermal conductivity and response, portable calorimeters cannot be practically used with high-current accelerators, where product conveyor speeds under an electron beam can exceed several meters per second and the calorimeter is not suitable for use with product handling systems. As an alternative, Monte Carlo calculations can give theoretical estimates of the absorbed dose in materials with flat or complex configurations such that the results are independent of dose-rate. Monte Carlo results can then be compared to experimental dose determinations to see whether dose-rate effects in the dosimeters are significant. A Monte Carlo code has been used in this study to calculate the absorbed doses in alanine film dosimeters supported by flat sheets of plywood irradiated with electrons using incident energies extending from 1.0 MeV to 10 MeV with beam currents up to 30 mA. The same process conditions have been used for dose determinations with high-current electron beams using low dose-rate gamma calibrated alanine film dosimeters. The close agreement between these calculations and the dosimeter determinations indicates that the response of this type of dosimeter system is independent of the dose-rate, and provides assurance that Monte Carlo calculations can yield results with sufficient accuracy for many industrial applications.

  16. Understanding the catalyst-free transformation of amorphous carbon into graphene by current-induced annealing

    PubMed Central

    Barreiro, Amelia; Börrnert, Felix; Avdoshenko, Stanislav M.; Rellinghaus, Bernd; Cuniberti, Gianaurelio; Rümmeli, Mark H.; Vandersypen, Lieven M. K.

    2013-01-01

    We shed light on the catalyst-free growth of graphene from amorphous carbon (a–C) by current-induced annealing by witnessing the mechanism both with in-situ transmission electron microscopy and with molecular dynamics simulations. Both in experiment and in simulation, we observe that small a–C clusters on top of a graphene substrate rearrange and crystallize into graphene patches. The process is aided by the high temperatures involved and by the van der Waals interactions with the substrate. Furthermore, in the presence of a–C, graphene can grow from the borders of holes and form a seamless graphene sheet, a novel finding that has not been reported before and that is reproduced by the simulations as well. These findings open up new avenues for bottom-up engineering of graphene-based devices.

  17. Effect of high current electron beam in a 30 MeV radio frequency linac for neutron-time-of-flight applications

    NASA Astrophysics Data System (ADS)

    Nayak, B.; Acharya, S.; Rajawat, R. K.; DasGupta, K.

    2016-01-01

    A high power pulsed radio frequency electron linac is designed by BARC, India to accelerate 30 MeV, 10 A, 10 ns beam for neutron-time-of-flight applications. It will be used as a neutron generator and will produce ˜1012-1013 n/s. It is essential to reduce the beam instability caused by space charge effect and the beam cavity interaction. In this paper, the wakefield losses in the accelerating section due to bunch of RMS (Root mean square) length 2 mm (at the gun exit) is analysed. Loss and kick factors are numerically calculated using CST wakefield solver. Both the longitudinal and transverse wake potentials are incorporated in beam dynamics code ELEGANT to find the transverse emittance growth of the beam propagating through the linac. Beam loading effect is examined by means of numerical computation carried out in ASTRA code. Beam break up start current has been estimated at the end of the linac which arises due to deflecting modes excited by the high current beam. At the end, transverse beam dynamics of such high current beam has been analysed.

  18. Analysis of current density and specific absorption rate in biological tissue surrounding transcutaneous transformer for an artificial heart.

    PubMed

    Shiba, Kenji; Nukaya, Masayuki; Tsuji, Toshio; Koshiji, Kohji

    2008-01-01

    This paper reports on the current density and specific absorption rate (SAR) analysis of biological tissue surrounding an air-core transcutaneous transformer for an artificial heart. The electromagnetic field in the biological tissue is analyzed by the transmission line modeling method, and the current density and SAR as a function of frequency, output voltage, output power, and coil dimension are calculated. The biological tissue of the model has three layers including the skin, fat, and muscle. The results of simulation analysis show SARs to be very small at any given transmission conditions, about 2-14 mW/kg, compared to the basic restrictions of the International Commission on nonionizing radiation protection (ICNIRP; 2 W/kg), while the current density divided by the ICNIRP's basic restrictions gets smaller as the frequency rises and the output voltage falls. It is possible to transfer energy below the ICNIRP's basic restrictions when the frequency is over 250 kHz and the output voltage is under 24 V. Also, the parts of the biological tissue that maximized the current density differ by frequencies; in the low frequency is muscle and in the high frequency is skin. The boundary is in the vicinity of the frequency 600-1000 kHz. PMID:18232363

  19. Controlling precise magnetic field configuration around electron cyclotron resonance zone for enhancing plasma parameters and beam current

    SciTech Connect

    Yano, Keisuke Kurisu, Yosuke; Nozaki, Dai; Kimura, Daiju; Imai, Youta; Kumakura, Sho; Sato, Fuminobu; Kato, Yushi; Iida, Toshiyuki

    2014-02-15

    Multi-charged ion source which has wide operating conditions is required in various application fields. We have constructed tandem type ECR ion source (ECRIS); one of the features of its main stage is an additional coil for controlling magnetic field distribution around the mirror bottom precisely. Here the effect of magnetic field variation caused by the additional coil is experimentally considered in terms of plasma parameters and beam current as the first investigation of the main stage plasma. Furthermore, behavior of magnetic lines of force flowing from the ECR zone is calculated, and is compared with measurement results aiming for better understanding of interrelationship between plasma production and ion beam generation on the ECRIS.

  20. Overview of Alternative Bunching and Current-shaping Techniques for Low-Energy Electron Beams

    SciTech Connect

    Piot, Philippe

    2015-12-01

    Techniques to bunch or shape an electron beam at low energies (E <15 MeV) have important implications toward the realization of table-top radiation sources [1] or to the design of compact multi-user free-electron lasers[2]. This paper provides an overview of alternative methods recently developed including techniques such as wakefield-based bunching, space-charge-driven microbunching via wave-breaking [3], ab-initio shaping of the electron-emission process [4], and phase space exchangers. Practical applications of some of these methods to foreseen free-electron-laser configurations are also briefly discussed [5].

  1. Change in Ion Beam Induced Current from Si Metal-Oxide-Semiconductor Capacitors after Gamma-Ray Irradiation

    SciTech Connect

    Ohshima, T.; Onoda, S.; Hirao, T.; Takahashi, Y.; Vizkelethy, G.; Doyle, B. L.

    2009-03-10

    To investigate the effects of gamma-ray irradiation on transient current induced in MOS capacitors by heavy ion incidence, Si MOS capacitors were irradiated with gamma-rays up to 60.9 kGy(SiO2). The change in Transient Ion Beam Induced Current (TIBIC) signals due to gamma-ray irradiation was investigated using 15 MeV-oxygen ion microbeams. After gamma-ray irradiation, the peak current of the TIBIC signal vs. bias voltage curve shifted toward negative voltages. This shift can be interpreted in terms of the charge trapped in the oxide. In this dose range, no significant effects of the interface traps induced by gamma-ray irradiation on the TIBIC signals were observed.

  2. Beam Interaction Measurements with a Retarding Field Analyzer in a High-Current High-Vacuum Positively-Charged Particle Accelerator

    SciTech Connect

    Covo, M K; Molvik, A W; Friedman, A; Barnard, J J; Seidl, P A; Logan, B G; Baca, D; Vujic, J L

    2006-07-11

    A Retarding Field Analyzer (RFA) was inserted in a drift region of a magnetic transport section of the high-current experiment (HCX) that is at high-vacuum to measure ions and electrons resulting from beam interaction with background gas and walls. The ions are expelled during the beam by the space-charge potential and the electrons are expelled mainly at the end of the beam, when the beam potential decays. The ion energy distribution shows the beam potential of {approx} 2100 V and the beam-background gas total cross-section of 1.6x10{sup -20} m{sup 2}. The electron energy distribution reveals that the expelled electrons are mainly desorbed from the walls and gain {approx} 22 eV from the beam potential decaying with time before entering the RFA. Details of the RFA design and of the measured energy distributions are presented and discussed.

  3. A Fourier transform spectrometer without a beam splitter for the vacuum ultraviolet range: From the optical design to the first UV spectrum

    SciTech Connect

    Oliveira, N. de; Polack, F.; Vervloet, M.; Nahon, L.; Joyeux, D.; Phalippou, D.; Rodier, J. C.

    2009-04-15

    We describe a Fourier transform (FT) spectrometer designed to operate down to 60 nm (20 eV) on a synchrotron radiation beamline for high resolution absorption spectrometry. As far as we know, such an instrument is not available below 140 nm mainly because manufacturing accurate and efficient beam splitters remains a major problem at these wavelengths, especially if a wide bandwidth operation is desired. In order to overcome this difficulty, we developed an interferometer based on wave front division instead of amplitude division. It relies on a modified Fresnel bimirror configuration that requires only flat mirrors. The instrument provides path difference scanning through the translation of one reflector. During the scanning, the moving reflector is controlled by an optical system that keeps its direction constant within a tolerable value and provides an accurate interferometric measurement of the path difference variation. Therefore, a regular interferogram sampling is obtained, producing a nominal spectral impulse response and an accurate spectral calibration. The first results presented in this paper show a measured spectral resolution of {delta}{sigma}=0.33 cm{sup -1} (interval between spectral samples). This was obtained with a sampling interval of 29 nm (path difference) and 512 K samples from a one-sided interferogram using a cosine FT. Such a sampling interval should allow the recording of large bandwidth spectra down to {lambda}=58 nm with an ultimate resolving power of 500 000 at this wavelength. In order to check the instrument performances, we first recorded an interferogram from a He-Ne stabilized laser. This provided the actual spectral impulse function, which was found to be fully satisfactory. The determination of the impulse response distortion and of the noise on the vacuum ultraviolet (VUV) spectral range provided accurate information in the sampling error profile over a typical scan. Finally, the instrument has been moved to the SU5 undulator

  4. A Fourier transform spectrometer without a beam splitter for the vacuum ultraviolet range: From the optical design to the first UV spectrum

    NASA Astrophysics Data System (ADS)

    de Oliveira, N.; Joyeux, D.; Phalippou, D.; Rodier, J. C.; Polack, F.; Vervloet, M.; Nahon, L.

    2009-04-01

    We describe a Fourier transform (FT) spectrometer designed to operate down to 60 nm (20 eV) on a synchrotron radiation beamline for high resolution absorption spectrometry. As far as we know, such an instrument is not available below 140 nm mainly because manufacturing accurate and efficient beam splitters remains a major problem at these wavelengths, especially if a wide bandwidth operation is desired. In order to overcome this difficulty, we developed an interferometer based on wave front division instead of amplitude division. It relies on a modified Fresnel bimirror configuration that requires only flat mirrors. The instrument provides path difference scanning through the translation of one reflector. During the scanning, the moving reflector is controlled by an optical system that keeps its direction constant within a tolerable value and provides an accurate interferometric measurement of the path difference variation. Therefore, a regular interferogram sampling is obtained, producing a nominal spectral impulse response and an accurate spectral calibration. The first results presented in this paper show a measured spectral resolution of δσ =0.33 cm-1 (interval between spectral samples). This was obtained with a sampling interval of 29 nm (path difference) and 512 K samples from a one-sided interferogram using a cosine FT. Such a sampling interval should allow the recording of large bandwidth spectra down to λ&dotbelow;>=58 nm with an ultimate resolving power of 500 000 at this wavelength. In order to check the instrument performances, we first recorded an interferogram from a He-Ne stabilized laser. This provided the actual spectral impulse function, which was found to be fully satisfactory. The determination of the impulse response distortion and of the noise on the vacuum ultraviolet (VUV) spectral range provided accurate information in the sampling error profile over a typical scan. Finally, the instrument has been moved to the SU5 undulator

  5. Collective acceleration of electrons and ions in a high current relativistic electron beam. Final report

    SciTech Connect

    Nation, J.A.

    1992-12-31

    This report describes work carried out on DOE contract number DE-AC02-80ER10569 during the period December 15, 1979 to May 31, 1992. The original purpose of this research was to investigate the use of slow space charge waves on weakly relativistic electron beams for ion acceleration. The work had three major objectives: development of a suitable ion injector, growth and study of the properties of slow space charge waves on an electron beam, and a combination of the two components into a suitable proof-of-principle demonstration of the wave accelerator. Work focused on the first two of these objectives. Control of the space charge waves` phase velocity was not obtained to the degree required for a working accelerator, so the project was duly terminated in favor of a program which focused on generating ultra high power microwave signals suitable for use in the next linear collider. Work done to develop suitable efficient, inexpensive, phase-stable microwave sources, with peak powers of up to 1 GW in the X band in pulses shorter than 1 ns, is described. Included are lists of the journal and conference papers resulting from this work, as well as a list of graduate students who completed their Ph.D. studies on the projects described in this report.

  6. Design of a high-current low-energy beam transport line for an intense D-T/D-D neutron generator

    NASA Astrophysics Data System (ADS)

    Lu, Xiaolong; Wang, Junrun; Zhang, Yu; Li, Jianyi; Xia, Li; Zhang, Jie; Ding, Yanyan; Jiang, Bing; Huang, Zhiwu; Ma, Zhanwen; Wei, Zheng; Qian, Xiangping; Xu, Dapeng; Lan, Changlin; Yao, Zeen

    2016-03-01

    An intense D-T/D-D neutron generator is currently being developed at the Lanzhou University. The Cockcroft-Walton accelerator, as a part of the neutron generator, will be used to accelerate and transport the high-current low-energy beam from the duoplasmatron ion source to the rotating target. The design of a high-current low-energy beam transport (LEBT) line and the dynamics simulations of the mixed beam were carried out using the TRACK code. The results illustrate that the designed beam line facilitates smooth transportation of a deuteron beam of 40 mA, and the number of undesired ions can be reduced effectively using two apertures.

  7. Review on δ-Transformation-Induced Plasticity (TRIP) Steels with Low Density: The Concept and Current Progress

    NASA Astrophysics Data System (ADS)

    Yi, H. L.

    2014-09-01

    Novel alloys with high aluminum addition, so-called δ-transformation-induced plasticity (TRIP), have been developed recently for the third generation of advanced high strength steels for automotive applications, which are promising owing to the potential weldability as well as the combination of strength and ductility. In addition, the high aluminum addition results in a density reduction of approximately 5% in these δ-TRIP alloys without sacrificing the Young's modulus in uniaxial tensile tests. The origin of δ-TRIP concept is introduced first with a review of the published work on δ-TRIP alloys. This review will include methodology for retention of δ-ferrite in casting, rolling and welding conditions, microstructure evolution by austempering, as well as microstructures-properties relationship involving the roles of blocky and lath retained austenite. In addition, currently unresolved problems will be discussed regarding the fundamentals of materials design, automotive application, and industrial manufacturing.

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

    PubMed

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

    2009-02-01

    This paper presents the construction of carbon-fiber-aluminum (CFA) cathode by squeezing casting and its applications for generating high-current electron beams to drive high-power microwave sources. The fabrication process avoided using epoxy, a volatile deteriorating the vacuum system. These cathodes had a higher hardness than conventional aluminum, facilitating machining. After surface treatment, carbon fibers became the dominator determining emission property. A multineedle CFA cathode was utilized in a triode virtual cathode oscillator (vircator), powered by a approximately 450 kV, approximately 400 ns pulse. It was found that 300-400 MW, approximately 250 ns microwave was radiated at a dominant frequency of 2.6 GHz. Further, this cathode can endure high-current-density emission without detectable degradation in performance as the pulse shot proceeded, showing the robust nature of carbon fibers as explosive emitters. Overall, this new class of cold cathodes offers a potential prospect of developing high-current electron beam sources. PMID:19256641

  9. An annular high-current electron beam with an energy spread in a coaxial magnetically insulated diode

    NASA Astrophysics Data System (ADS)

    Grishkov, A. A.; Pegel, I. V.

    2013-11-01

    An elementary theory of an annular high-current electron beam in a uniform transport channel and a coaxial magnetically insulated diode is generalized to the case of counterpropagating electron beams with a spread over kinetic energies. Expressions for the sum of the absolute values of the forward and backward currents in a uniform transport channel and for the flux of the longitudinal component of the generalized momentum in a coaxial magnetically insulated diode as functions of the maximum electron kinetic energy are derived for different values of the relative width of the energy distribution function. It is shown that, in a diode with an expanding transport channel and a virtual cathode limiting the extracted current, counterpropagating particle flows are established between the cathode and the virtual cathode within a certain time interval after the beginning of electron emission. The accumulation of electrons in these flows is accompanied by an increase in their spread over kinetic energies and the simultaneous decrease in the maximum kinetic energy. The developed model agrees with the results of particle-in-cell simulations performed using the KARAT and OOPIC-Pro codes.

  10. Determination of minority-carrier diffusion length by integral properties of electron-beam-induced current profiles

    NASA Astrophysics Data System (ADS)

    Cavalcoli, D.; Cavallini, A.; Castaldini, A.

    1991-08-01

    The diffusion length of minority carriers in n-type floating-zone Si samples is obtained with the electron-beam-induced current technique in planar configuration. The charge collection current data as a function of the beam-junction distance are analyzed on the basis of the ``moment method'' developed by Donolato [C. Donolato, Solid-State Electron. 28, 1143 (1985)], which is based on the calculation of the variance of the derivative of the current profile. With respect to other methods reported in literature, this has the advantage that it requires no assumptions on the surface recombination velocity and thus provides a diffusion length value free from its influence. The data are also analyzed with the asymptotic method, which requires conventional assumptions on the surface recombination velocity. The comparison between the results has allowed us to test the capabilities of the above-mentioned method. Particular attention is paid to the injection level and its influence on bulk and surface properties.

  11. An annular high-current electron beam with an energy spread in a coaxial magnetically insulated diode

    SciTech Connect

    Grishkov, A. A. Pegel, I. V.

    2013-11-15

    An elementary theory of an annular high-current electron beam in a uniform transport channel and a coaxial magnetically insulated diode is generalized to the case of counterpropagating electron beams with a spread over kinetic energies. Expressions for the sum of the absolute values of the forward and backward currents in a uniform transport channel and for the flux of the longitudinal component of the generalized momentum in a coaxial magnetically insulated diode as functions of the maximum electron kinetic energy are derived for different values of the relative width of the energy distribution function. It is shown that, in a diode with an expanding transport channel and a virtual cathode limiting the extracted current, counterpropagating particle flows are established between the cathode and the virtual cathode within a certain time interval after the beginning of electron emission. The accumulation of electrons in these flows is accompanied by an increase in their spread over kinetic energies and the simultaneous decrease in the maximum kinetic energy. The developed model agrees with the results of particle-in-cell simulations performed using the KARAT and OOPIC-Pro codes.

  12. High-Resolution X-Ray and Light Beam Induced Current (LBIC) Measurements of Multcrystalline Silicon Solar Cells

    SciTech Connect

    Jellison Jr, Gerald Earle; Budai, John D; Bennett, Charlee J C; Tischler, Jonathan Zachary; Duty, Chad E; Yelundur, V.; Rohatgi, A.

    2010-01-01

    High-resolution, spatially-resolved x-ray Laue patterns and high-resolution light beam induced current (LBIC) measurements are combined to study two multicrystalline solar cells made from the Heat Exchanger Method (HEM) and the Sting Ribbon Growth technique. The LBIC measurements were made at 4 different wavelengths (488, 633, 780, and 980 nm), resulting in penetration depths ranging from <1 {mu}m to >100 {mu}m. There is a strong correlation between the x-ray and LBIC measurements, showing that some twins and grain boundaries are effective in the reduction of local quantum efficiency, while others are benign.

  13. The influence of guiding magnetic field on beam current and plasma expansion in foil-less diode

    SciTech Connect

    Wu, Ping; Ye, Hu; Sun, Jun

    2015-06-15

    The impedance collapse phenomenon in planar diodes has been widely investigated and is believed to be induced by the axial plasma expansion. However, there are few studies about the impedance collapse phenomenon in foil-less diodes, which may occur under a low guiding magnetic field and cannot be explained by the axial plasma expansion. This paper tries to explain this phenomenon by constructing a physical model with consideration of the radial expansion of cathode plasmas. Our physical model can quantitatively describe the formation process of beam current in experiments with reasonable parameters, and it demonstrates that a lower guiding magnetic field will lead to a faster radial plasma expansion speed.

  14. On-line measurements of proton beam current from a PET cyclotron using a thin aluminum foil

    NASA Astrophysics Data System (ADS)

    Ghithan, S.; do Carmo, S. J. C.; Ferreira Marques, R.; Fraga, F. A. F.; Simões, H.; Alves, F.; Crespo, P.

    2013-07-01

    The number of cyclotrons capable of accelerating protons to about 20 MeV is increasing throughout the world. Originally aiming at the production of positron emission tomography (PET) radionuclides, some of these facilities are equipped with several beam lines suitable for scientific research. Radiobiology, radiophysiology, and other dosimetric studies can be performed using these beam lines. In this work, we measured the Bragg peak of the protons from a PET cyclotron using a stacked target consisting of several aluminum foils interleaved with polyethylene sheets, readout by in-house made transimpedance electronics. The measured Bragg peak is consistent with simulations performed using the SRIM/TRIM simulation toolkit. Furthermore, we report on experimental results aiming at measuring proton beam currents down to 10 pA using a thin aluminum foil (20-μm-thick). The aluminum was chosen for this task because it is radiation hard, it has low density and low radiation activity, and finally because it is easily available at negligible cost. This method allows for calculating the dose delivered to a target during an irradiation with high efficiency, and with minimal proton energy loss and scattering.

  15. Current-driven ion-acoustic and potential-relaxation instabilities excited in plasma plume during electron beam welding

    SciTech Connect

    Trushnikov, D. N.; Mladenov, G. M. Koleva, E. G.; Belenkiy, V. Ya. Varushkin, S. V.

    2014-04-15

    Many papers have sought correlations between the parameters of secondary particles generated above the beam/work piece interaction zone, dynamics of processes in the keyhole, and technological processes. Low- and high-frequency oscillations of the current, collected by plasma have been observed above the welding zone during electron beam welding. Low-frequency oscillations of secondary signals are related to capillary instabilities of the keyhole, however; the physical mechanisms responsible for the high-frequency oscillations (>10 kHz) of the collected current are not fully understood. This paper shows that peak frequencies in the spectra of the collected high-frequency signal are dependent on the reciprocal distance between the welding zone and collector electrode. From the relationship between current harmonics frequency and distance of the collector/welding zone, it can be estimated that the draft velocity of electrons or phase velocity of excited waves is about 1600 m/s. The dispersion relation with the properties of ion-acoustic waves is related to electron temperature 10 000 K, ion temperature 2 400 K and plasma density 10{sup 16} m{sup −3}, which is analogues to the parameters of potential-relaxation instabilities, observed in similar conditions. The estimated critical density of the transported current for creating the anomalous resistance state of plasma is of the order of 3 A·m{sup −2}, i.e. 8 mA for a 3–10 cm{sup 2} collector electrode. Thus, it is assumed that the observed high-frequency oscillations of the current collected by the positive collector electrode are caused by relaxation processes in the plasma plume above the welding zone, and not a direct demonstration of oscillations in the keyhole.

  16. First plasma of megawatt high current ion source for neutral beam injector of the experimental advanced superconducting tokamak on the test bed

    SciTech Connect

    Hu Chundong; Xie Yahong; Liu Sheng; Xie Yuanlai; Jiang Caichao; Song Shihua; Li Jun; Liu Zhimin

    2011-02-15

    High current ion source is the key part of the neutral beam injector. In order to develop the project of 4 MW neutral beam injection for the experimental advanced superconducting tokamak (EAST) on schedule, the megawatt high current ion source is prestudied in the Institute of Plasma Physics in China. In this paper, the megawatt high current ion source test bed and the first plasma are presented. The high current discharge of 900 A at 2 s and long pulse discharge of 5 s at 680 A are achieved. The arc discharge characteristic of high current ion source is analyzed primarily.

  17. Coupling of mechanical dynamics and induced currents in a cantilever beam

    SciTech Connect

    Bialek, J.M.; Weissenburger, D.W.

    1985-01-01

    Electrical eddy currents induced in a conducting structure subjected to a background magnetic field produce forces which may result in significant mechanical reactions and deflections. The dynamics of the conductive structure are modified by additional eddy currents which are induced by the structural motion. Frequently, the observed effects of these secondary eddy currents are referred to as magnetic damping and magnetic stiffness. A coupled system of equations was formulated using finite element techniques for the mechanical aspects and a mesh network method for the electrical aspects of the problem. The eigenvalues of the governing equations are examined using the background magnetic field as a parameter, and the solution of the equations is presented for a sample problem. The expected effects of magnetic damping and magnetic stiffness are observed in the solutions of the coupled equations.

  18. Electron-beam-deposited thin polymer films - Electrical properties vs bombarding current.

    NASA Technical Reports Server (NTRS)

    Babcock, L. E.; Christy, R. W.

    1972-01-01

    Polymer films about 150 A thick, deposited on glass substrates by electron bombardment of tetramethyltetraphenyltrisiloxane, were studied, after being sandwiched between evaporated aluminum electrodes, the top one semitransparent. The capacitance, conductance, and photoconductance of the sandwiches were measured at room temperature as a function of the electron bombarding current which formed the polymer. The polymer thickness was obtained independently from Christy's (1960) empirical formula for the rate of formation. The obtained results indicate that, with increasing bombarding current, the polymer undergoes an increase in both crosslinking bonds and dangling bonds. Exposure to air drastically reduces the density of dangling bonds, but does not affect the crosslinking.

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

    SciTech Connect

    Ward, Kevin S.; Long, Finis W.; Sinebryukhov, Vadim A. , Tomsk, Russia); Kim, Alexandre A. , Tomsk, Russia); Wakeland, Peter Eric; McKee, G. Randall; Woodworth, Joseph Ray; McDaniel, Dillon Heirman; Fowler, William E.; Mazarakis, Michael Gerrassimos; Porter, John Larry, Jr.; Struve, Kenneth William; Savage, Mark Edward; Stygar, William A.; LeChien, Keith R.; Matzen, Maurice Keith

    2010-09-01

    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

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

    SciTech Connect

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

    2014-02-15

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

  1. Development of a low-energy and high-current pulsed neutral beam injector with a washer-gun plasma source for high-beta plasma experiments.

    PubMed

    Ii, Toru; Gi, Keii; Umezawa, Toshiyuki; Asai, Tomohiko; Inomoto, Michiaki; Ono, Yasushi

    2012-08-01

    We have developed a novel and economical neutral-beam injection system by employing a washer-gun plasma source. It provides a low-cost and maintenance-free ion beam, thus eliminating the need for the filaments and water-cooling systems employed conventionally. In our primary experiments, the washer gun produced a source plasma with an electron temperature of approximately 5 eV and an electron density of 5 × 10(17) m(-3), i.e., conditions suitable for ion-beam extraction. The dependence of the extracted beam current on the acceleration voltage is consistent with space-charge current limitation, because the observed current density is almost proportional to the 3/2 power of the acceleration voltage below approximately 8 kV. By optimizing plasma formation, we successfully achieved beam extraction of up to 40 A at 15 kV and a pulse length in excess of 0.25 ms. Its low-voltage and high-current pulsed-beam properties enable us to apply this high-power neutral beam injection into a high-beta compact torus plasma characterized by a low magnetic field. PMID:22938291

  2. Development of a low-energy and high-current pulsed neutral beam injector with a washer-gun plasma source for high-beta plasma experiments

    NASA Astrophysics Data System (ADS)

    Ii, Toru; Gi, Keii; Umezawa, Toshiyuki; Asai, Tomohiko; Inomoto, Michiaki; Ono, Yasushi

    2012-08-01

    We have developed a novel and economical neutral-beam injection system by employing a washer-gun plasma source. It provides a low-cost and maintenance-free ion beam, thus eliminating the need for the filaments and water-cooling systems employed conventionally. In our primary experiments, the washer gun produced a source plasma with an electron temperature of approximately 5 eV and an electron density of 5 × 1017 m-3, i.e., conditions suitable for ion-beam extraction. The dependence of the extracted beam current on the acceleration voltage is consistent with space-charge current limitation, because the observed current density is almost proportional to the 3/2 power of the acceleration voltage below approximately 8 kV. By optimizing plasma formation, we successfully achieved beam extraction of up to 40 A at 15 kV and a pulse length in excess of 0.25 ms. Its low-voltage and high-current pulsed-beam properties enable us to apply this high-power neutral beam injection into a high-beta compact torus plasma characterized by a low magnetic field.

  3. Study on the nanostructure formation mechanism of hypereutectic Al-17.5Si alloy induced by high current pulsed electron beam

    NASA Astrophysics Data System (ADS)

    Gao, Bo; Hu, Liang; Li, Shi-wei; Hao, Yi; Zhang, Yu-dong; Tu, Gan-feng; Grosdidier, Thierry

    2015-08-01

    This work investigates the nanostructure forming mechanism of hypereutectic Al-17.5Si alloy associated with the high current pulsed electron beam (HCPEB) treatment with increasing number of pulses by electron backscatter diffraction (EBSD) and SEM. The surface layers were melted and resolidified rapidly. The treated surfaces show different structural characteristics in different compositions and distribution zones. The top melted-layer zone can be divided into three zones: Si-rich, Ai-rich, and intermediate zone. The Al-rich zone has a nano-cellular microstructure with a diameter of ∼100 nm. The microstructure in the Si-rich zone consists of fine, dispersive, and spherical nano-sized Si crystals surrounded by α(Al) cells. Some superfine eutectic structures form in the boundary of the two zones. With the increase of number of pulses, the proportion of Si-rich zone to the whole top surface increases, and more cellular substructures are transformed to fine equiaxed grain. In other words, with increasing number of pulses, more Si elements diffuse to the Al-rich zone and provide heterogeneous nucleation sites, and Al grains are refined dramatically. Moreover, the relationship between the substrate Si phase and crystalline phase is determined by EBSD; that is, (1 1 1)Al//(0 0 1)Si with a value of disregistry δ at approximately 5%. The HCPEB technique is a versatile technique for refining the surface microstructure of hypereutectic Al-Si alloys.

  4. Polarity inversion and coupling of laser beam induced current in As-doped long-wavelength HgCdTe infrared detector pixel arrays: Experiment and simulation

    NASA Astrophysics Data System (ADS)

    Hu, W. D.; Chen, X. S.; Ye, Z. H.; Chen, Y. G.; Yin, F.; Zhang, B.; Lu, W.

    2012-10-01

    In this paper, experimental results of polarity inversion and coupling of laser beam induced current for As-doped long-wavelength HgCdTe pixel arrays grown on CdZnTe are reported. Models for the p-n junction transformation are proposed and demonstrated using numerical simulations. Simulation results are shown to be in agreement with the experimental results. It is found that the deep traps induced by ion implantation are very sensitive to temperature, resulting in a decrease of the quasi Fermi level in the implantation region in comparison to that in the Hg interstitials diffusion and As-doped regions. The Hg interstitial diffusion, As-doping amphoteric behavior, ion implantation damage traps, and the mixed conduction, are key factors for inducing the polarity reversion, coupling, and junction broadening at different temperatures. The results provide the near room-temperature HgCdTe photovoltaic detector with a reliable reference on the junction reversion and broadening around implanted regions, as well as controlling the n-on-p junction for very long wavelength HgCdTe infrared detector pixels.

  5. Studies and optimization of Pohang Light Source-II superconducting radio frequency system at stable top-up operation with beam current of 400 mA

    SciTech Connect

    Joo, Youngdo Yu, Inha; Park, Insoo; Chun, Myunghwan; Lee, Byung-Joon; Hwang, Ilmoon; Ha, Taekyun; Shin, Seunghwan; Sohn, Younguk

    2014-12-21

    After three years of upgrading work, the Pohang Light Source-II (PLS-II) is now successfully operating. The final quantitative goal of PLS-II is a top-up user-service operation with beam current of 400 mA to be completed by the end of 2014. During the beam store test up to 400 mA in the storage ring (SR), it was observed that the vacuum pressure around the radio frequency (RF) window of the superconducting cavity rapidly increases over the interlock level limiting the availability of the maximum beam current storing. Although available beam current is enhanced by setting a higher RF accelerating voltage, it is better to keep the RF accelerating voltage as low as possible in the long time top-up operation. We investigated the cause of the window vacuum pressure increment by studying the changes in the electric field distribution at the superconducting cavity and waveguide according to the beam current. In our simulation, an equivalent physical modeling was developed using a finite-difference time-domain code. The simulation revealed that the electric field amplitude at the RF window is exponentially increased as the beam current increases, thus this high electric field amplitude causes a RF breakdown at the RF window, which comes with the rapid increase of window vacuum pressure. The RF accelerating voltage of PLS-II RF system was set to 4.95 MV, which was estimated using the maximum available beam current that works as a function of RF voltage, and the top-up operation test with the beam current of 400 mA was successfully carried out.

  6. Simulation of ion beam induced current in radiation detectors and microelectronic devices.

    SciTech Connect

    Vizkelethy, Gyorgy

    2009-10-01

    Ionizing radiation is known to cause Single Event Effects (SEE) in a variety of electronic devices. The mechanism that leads to these SEEs is current induced by the radiation in these devices. While this phenomenon is detrimental in ICs, this is the basic mechanism behind the operation of semiconductor radiation detectors. To be able to predict SEEs in ICs and detector responses we need to be able to simulate the radiation induced current as the function of time. There are analytical models, which work for very simple detector configurations, but fail for anything more complex. On the other end, TCAD programs can simulate this process in microelectronic devices, but these TCAD codes costs hundreds of thousands of dollars and they require huge computing resources. In addition, in certain cases they fail to predict the correct behavior. A simulation model based on the Gunn theorem was developed and used with the COMSOL Multiphysics framework.

  7. Transition from Beam-Target to Thermonuclear Fusion in High-Current Deuterium Z -Pinch Simulations

    NASA Astrophysics Data System (ADS)

    Offermann, Dustin T.; Welch, Dale R.; Rose, Dave V.; Thoma, Carsten; Clark, Robert E.; Mostrom, Chris B.; Schmidt, Andrea E. W.; Link, Anthony J.

    2016-05-01

    Fusion yields from dense, Z -pinch plasmas are known to scale with the drive current, which is favorable for many potential applications. Decades of experimental studies, however, show an unexplained drop in yield for currents above a few mega-ampere (MA). In this work, simulations of DD Z -Pinch plasmas have been performed in 1D and 2D for a constant pinch time and initial radius using the code Lsp, and observations of a shift in scaling are presented. The results show that yields below 3 MA are enhanced relative to pure thermonuclear scaling by beamlike particles accelerated in the Rayleigh-Taylor induced electric fields, while yields above 3 MA are reduced because of energy lost by the instability and the inability of the beamlike ions to enter the pinch region.

  8. Simulation of ion beam induced current in radiation detectors and microelectronic devices.

    SciTech Connect

    Vizkelethy, Gyorgy

    2010-07-01

    Ionizing radiation is known to cause Single Event Effects (SEE) in a variety of electronic devices. The mechanism that leads to these SEEs is current induced by the radiation in these devices. While this phenomenon is detrimental in ICs, this is the basic mechanism behind the operation of semiconductor radiation detectors. To be able to predict SEEs in ICs and detector responses we need to be able to simulate the radiation induced current as the function of time. There are analytical models, which work for very simple detector configurations, but fail for anything more complex. On the other end, TCAD programs can simulate this process in microelectronic devices, but these TCAD codes costs hundreds of thousands of dollars and they require huge computing resources. In addition, in certain cases they fail to predict the correct behavior. A simulation model based on the Gunn theorem was developed and used with the COMSOL Multiphysics framework.

  9. High-dose external beam radiation for localized prostate cancer: current status and future challenges.

    PubMed

    Nguyen, Paul L; Zietman, Anthony L

    2007-01-01

    Since the 1960s, external beam radiation has been one of the major curative treatment options for patients with clinically localized prostate cancer. Efforts to improve the efficacy of this modality have focused on delivering a higher dose, and several recent randomized trials have confirmed that this higher dose results in improved oncological outcomes, particularly for patients with intermediate-risk disease. Technological advancements over the past 2 decades have allowed highly conformal treatments that spare more normal tissue and reduce early and long-term treatment side effects. In a complementary fashion, methods have been developed for better real-time localization of the prostate such that radiation fields can be shifted before each treatment to match the daily shifts in the position of the target, leading to greater accuracy and allowing for smaller treatment margins that in turn will overlap with less normal tissue. With newer and more expensive technologies such as intensity-modulated radiation therapy and protons being used with increasing frequency for the treatment of prostate cancer, it becomes imperative to study the risks and benefits of each new modality so that informed cost-benefit decisions can be made. Similarly, there has been a growing interest in hypofractionation as a means of exploiting the supposed low alpha/beta ratio of prostate cancer to shorten overall treatment time and thereby improve convenience and lower costs. However, as with any new technology, it is necessary to proceed with caution in the arena of hypofractionation while we await the results of trials that will help us to determine the long-term risks and benefits of hypofractionation and whether biological assumptions about the underlying alpha/beta ratio can translate into a true clinical advantage. PMID:17921728

  10. Combined infrared multiphoton dissociation and electron-capture dissociation using co-linear and overlapping beams in Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Mihalca, Romulus; van der Burgt, Yuri E M; McDonnell, Liam A; Duursma, Marc; Cerjak, Iliya; Heck, Albert J R; Heeren, Ron M A

    2006-01-01

    A novel set-up for Fourier transform ion cyclotron resonance mass spectrometry (FTICR) is reported for simultaneous infrared multiphoton dissociation (IRMPD) and electron-capture dissociation (ECD). An unmodified electron gun ensures complete, on-axis overlap between the electron and the photon beams. The instrumentation, design and implementation of this novel approach are described. In this configuration the IR beam is directed into the ICR cell using a pneumatically actuated mirror inserted into the ion-optical path. Concept validation was made using different combinations of IRMPD and ECD irradiation events on two standard peptides. The ability to perform efficient IRMPD, ECD and especially simultaneous IRMPD and ECD using lower irradiation times is demonstrated. The increase in primary sequence coverage, with the combined IRMPD and ECD set-up, also increases the confidence in peptide and protein assignments. PMID:16705647

  11. Use of the Syrian hamster embryo cell transformation assay for carcinogenicity prediction of chemical currently being tested by the National Toxicology Program in rodent bioassays

    SciTech Connect

    Kerckaert, G.A.; LeBoeuf, R.A.; Isfort, R.J.; Brauninger, R.

    1996-10-01

    The Syrian hamster embryo (SHE) cell transformation assay was used to predict the carcinogenicity of 26 chemicals currently being tested in the rodent bioassay by the National Toxicology Program as part of its program titled {open_quotes}Strategies for Predicting Chemical Carcinogenesis in Rodents.{close_quotes} Of these 26 chemicals, 17 were found to be positive in the SHE cell transformation assay while 9 were negative. Carcinogenicity predictions were made for these chemicals, based upon the SHE cell transformation assay results. Our predictions will be compared with the rodent bioassay results as they become available. 11 refs., 2 tabs.

  12. Development of an all-permanent-magnet microwave ion source equipped with multicusp magnetic fields for high current proton beam production.

    PubMed

    Tanaka, M; Hara, S; Seki, T; Iga, T

    2008-02-01

    An all-permanent-magnet (APM) microwave hydrogen ion source was developed to reduce the size and to simplify structure of a conventional solenoid coil microwave ion source developed for reliability improvement of high current proton linac application systems. The difficulty in developing the APM source was sensitive dependence of the source performance on axial magnetic field in the microwave discharge chamber. It was difficult to produce high current proton beam stably without precise tuning of the magnetic field using solenoid coils. We lowered the sensitivity using multicusp magnetic fields for plasma confinement at the discharge chamber sidewall of the source. This enabled stable high current proton beam production with the APM microwave ion source with no tuning coil. The water cooling and the power supply for the coils are not necessary for the APM source, which leads to better reliability and system simplification. The outer diameter of the APM source was around 300 mm, which was 20% lower than the coil source. The APM source produced a maximum hydrogen ion beam current of 65 mA (high current density of 330 mA/cm(2), proton ratio of 87%, and beam energy of 30 keV) with a 5 mm diameter extraction aperture, pulse width of 400 micros, and 20 Hz repetition rate at 1.3 kW microwave power. This performance is almost the same as the best performances of the conventional coil sources. The extracted ion beams were focused with electrostatic five-grid lens to match beam to acceptance of radio-frequency quadrupole linacs. The maximum focused beam current through the orifice (5 mm radius) and the lens was 36 mA and the 90% focused beam half-width was 1-2 mm. PMID:18315183

  13. Diagnostics and electron-optics of a high current electron beam in the TANDEM free electron laser - status report

    SciTech Connect

    Arensburg, A.; Avramovich, A.; Chairman, D.

    1995-12-31

    In the construction of the Israeli TANDEM FEL the major task is to develop a high quality electron optic system. The goal is to focus the e-beam to a minimal radius (1 mm) in the interaction region (the wiggler). Furthermore, good focusing throughout the accelerator is essential in order to achieve high transport efficiency avoiding discharge and voltage drop of the high voltage terminal. We have completed the electron optical design and component procurement, including 8 quadrupole lenses 4 steering coils and an electrostatic control system. All are being assembled into the high voltage terminal and controlled by a fiber optic link. Diagnostic means based on fluorescent screens and compact CCD camera cards placed at the HV terminal and at the end of the e-gun injector have been developed. We report first measurements of the beam emittance at the entrance to the Tandem accelerator tube using the {open_quote}pepper pot{close_quote} technique. The experiment consists of passing the 0.5 Amp beam through a thin plate which is perforated with an army of 0.5 mm holes. The spots produced on a fluorescent screen placed 90 cm from the pepper pot were recorded with a CCD camera and a frame grabber. The measured normalized emittance is lower than 10{pi} mm mR which is quite close to the technical limit of dispenser cathode e-guns of the kind we have. Recent results of the measured transport efficiency and the diagnostics of the high current (1A, 1.5MV) electron-optical system will be reported.

  14. Characterization of plasma ion source utilizing anode spot with positively biased electrode for stable and high-current ion beam extraction

    SciTech Connect

    Park, Yeong-Shin; Lee, Yuna; Chung, Kyoung-Jae; Hwang, Y. S.

    2011-12-15

    The operating conditions of a rf plasma ion source utilizing a positively biased electrode have been investigated to develop a stably operating, high-current ion source. Ion beam characteristics such as currents and energies are measured and compared with bias currents by varying the bias voltages on the electrode immersed in the ambient rf plasma. Current-voltage curves of the bias electrode and photographs confirm that a small and dense plasma, so-called anode spot, is formed near an extraction aperture and plays a key role to enhance the performance of the plasma ion source. The ion beam currents from the anode spot are observed to be maximized at the optimum bias voltage near the knee of the characteristic current-voltage curve of the anode spot. Increased potential barrier to obstruct beam extraction is the reason for the reduction of the ion beam current in spite of the increased bias current indicating the density of the anode spot. The optimum bias voltage is measured to be lower at higher operating pressure, which is favorable for stable operation without severe sputtering damage on the electrode. The ion beam current can be further enhanced by increasing the power for the ambient plasma without increasing the bias voltage. In the same manner, noble gases with higher atomic number as a feedstock gas are preferable for extracting higher beam current more stably. Therefore, performance of the plasma ion source with a positively biased electrode can be enhanced by controlling the operating conditions of the anode spot in various manners.

  15. Optical beam induced current measurements based on two-photon absorption process in 4H-SiC bipolar diodes

    SciTech Connect

    Hamad, H.; Raynaud, C.; Bevilacqua, P.; Tournier, D.; Planson, D.; Vergne, B.

    2014-02-24

    Using a pulsed green laser with a wavelength of 532 nm, a duration pulse of ∼1 ns, and a mean power varying between 1 and 100 mW, induced photocurrents have been measured in 4H-SiC bipolar diodes. Considering the photon energy (2.33 eV) and the bandgap of 4H-SiC (3.2 eV), the generation of electron-hole pair by the conventional single photon absorption process should be negligible. The intensity of the measured photocurrents depends quadratically on the power beam intensity. This clearly shows that they are generated using two-photon absorption process. As in conventional OBIC (Optical Beam Induced Current), the measurements give an image of the electric field distribution in the structure under test, and the minority carrier lifetime can be extracted from the decrease of the photocurrent at the edge of the structure. The extracted minority carrier lifetime of 210 ns is consistent with results obtained in case of single photon absorption.

  16. Current interruption and particle beam generation by a plasma focus. Interim report (annual), 30 Sep 81-30 Sep 82

    SciTech Connect

    Gerdin, G.; Venneri, F.

    1982-11-30

    Through collaboration with Dr. K. H. Schoenbach of Texas Tech University the plasma focus opening switch (PFOS) was revised to answer basic questions as to utility of the concept. To estimate the plasma temperature and classical resistivity a soft X-ray spectrometer and X-ray pinhole camera were developed. The temperature was estimated from a coronal model to range between 0.4 to 0.5 keV for either a nitrogen or neon impurity (1 to 2%) in deuterium at 3 torr. Strong pinches were observed in pure neon (0.6 torr) with an electron temperature in the same range. The corresponding classical resistance of the pinch is 9 m omega whereas 500 m omega is more consistent with output voltage pulse and current flow at interruption indicating anomalous resistivity is present. A one-dimensional two-fluid computer code has been developed to model anomalous resistivity in the pinch phase and preliminary results are consistent with the snowplow model. The final analysis of the plasma focus particle beam generation experiments was completed and a strong correlation was found for the beam-target model as the mechanism for neutron production in the Illinois plasma focus device.

  17. X-ray framing camera for pulsed, high current, electron beam x-ray sources

    NASA Astrophysics Data System (ADS)

    Failor, B. H.; Rodriguez, J. C.; Riordan, J. C.; Lojewski, D. Y.

    2007-07-01

    High power x-ray sources built for nuclear weapons effects testing are evolving toward larger overall diameters and smaller anode cathode gaps. We describe a framing camera developed to measure the time-evolution of these 20-50 ns pulsed x-ray sources produced by currents in the 1.5-2.5 MA range and endpoint voltages between 0.2 and 1.5 MV. The camera has up to 4 frames with 5 ns gate widths; the frames are separated by 5 ns. The image data are recorded electronically with a gated intensified CCD camera and the data are available immediately following a shot. A fast plastic scintillator (2.1 ns decay time) converts the x-rays to visible light and, for high sensitivity, a fiber optic imaging bundle carries the light to the CCD input. Examples of image data are shown.

  18. Dosimetric properties of high energy current (HEC) detector in keV x-ray beams

    NASA Astrophysics Data System (ADS)

    Zygmanski, Piotr; Shrestha, Suman; Elshahat, Bassem; Karellas, Andrew; Sajo, Erno

    2015-04-01

    We introduce a new x-ray radiation detector. The detector employs high-energy current (HEC) formed by secondary electrons consisting predominantly of photoelectrons and Auger electrons, to directly convert x-ray energy to detector signal without externally applied power and without amplification. The HEC detector is a multilayer structure composed of thin conducting layers separated by dielectric layers with an overall thickness of less than a millimeter. It can be cut to any size and shape, formed into curvilinear surfaces, and thus can be designed for a variety of QA applications. We present basic dosimetric properties of the detector as function of x-ray energy, depth in the medium, area and aspect ratio of the detector, as well as other parameters. The prototype detectors show similar dosimetric properties to those of a thimble ionization chamber, which operates at high voltage. The initial results obtained for kilovoltage x-rays merit further research and development towards specific medical applications.

  19. Controlling Charge and Current Neutralization of an Ion Beam Pulse in a Background Plasma by Application of a Small Solenoidal Magnetic Field

    SciTech Connect

    Kaganovich, I. D.; Startsev, E. A.; Sefkow, A. B.; Davidson, R. C.

    2007-08-01

    Propagation of an intense charged particle beam pulse through a background plasma is a common problem in astrophysics and plasma applications. The plasma can effectively neutralize the charge and current of the beam pulse, and thus provides a convenient medium for beam transport. The application of a small solenoidal magnetic field can drastically change the self-magnetic and self-electric fields of the beam pulse, thus allowing effective control of the beam transport through the background plasma. An analytical model is developed to describe the self-magnetic field of a finite-length ion beam pulse propagating in a cold background plasma in a solenoidal magnetic field. The analytical studies show that the solenoidal magnetic field starts to influence the self-electric and self-magnetic fields when ωce ≥ ωpeβb, where ωce = eΒ/mec is the electron gyrofrequency, ωpe is the electron plasma frequency, and βb = Vb/c is the ion beam velocity relative to the speed of light. This condition typically holds for relatively small magnetic fields (about 100G). Analytical formulas are derived for the effective radial force acting on the beam ions, which can be used to minimize beam pinching. The results of analytical theory have been verified by comparison with the simulation results obtained from two particle-in-cell codes, which show good agreement.

  20. Controlling charge and current neutralization of an ion beam pulse in a background plasma by application of a solenoidal magnetic field: Weak magnetic field limit

    SciTech Connect

    Kaganovich, I. D.; Startsev, E. A.; Sefkow, A. B.; Davidson, R. C.

    2008-10-15

    Propagation of an intense charged particle beam pulse through a background plasma is a common problem in astrophysics and plasma applications. The plasma can effectively neutralize the charge and current of the beam pulse, and thus provides a convenient medium for beam transport. The application of a small solenoidal magnetic field can drastically change the self-magnetic and self-electric fields of the beam pulse, thus allowing effective control of the beam transport through the background plasma. An analytic model is developed to describe the self-magnetic field of a finite-length ion beam pulse propagating in a cold background plasma in a solenoidal magnetic field. The analytic studies show that the solenoidal magnetic field starts to influence the self-electric and self-magnetic fields when {omega}{sub ce} > or approx. {omega}{sub pe}{beta}{sub b}, where {omega}{sub ce}=eB/m{sub e}c is the electron gyrofrequency, {omega}{sub pe} is the electron plasma frequency, and {beta}{sub b}=V{sub b}/c is the ion beam velocity relative to the speed of light. This condition typically holds for relatively small magnetic fields (about 100 G). Analytical formulas are derived for the effective radial force acting on the beam ions, which can be used to minimize beam pinching. The results of analytic theory have been verified by comparison with the simulation results obtained from two particle-in-cell codes, which show good agreement.

  1. Controlling Charge and Current Neutralization of an Ion Beam Pulse in a Background Plasma by Application of a Solenoidal Magnetic Field I: Weak Magnetic Field Limit

    SciTech Connect

    Kaganovich, I. D., Startsev, E. A., Sefkow, A. B., Davidson, R. C.

    2008-10-10

    Propagation of an intense charged particle beam pulse through a background plasma is a common problem in astrophysics and plasma applications. The plasma can effectively neutralize the charge and current of the beam pulse, and thus provides a convenient medium for beam transport. The application of a small solenoidal magnetic field can drastically change the self-magnetic and self- electric fields of the beam pulse, thus allowing effective control of the beam transport through the background plasma. An analytic model is developed to describe the self-magnetic field of a finite- length ion beam pulse propagating in a cold background plasma in a solenoidal magnetic field. The analytic studies show that the solenoidal magnetic field starts to infuence the self-electric and self-magnetic fields when ωce > ωpeβb, where ωce = eβ/mec is the electron gyrofrequency, ωpe is the electron plasma frequency, and βb = Vb/c is the ion beam velocity relative to the speed of light. This condition typically holds for relatively small magnetic fields (about 100G). Analytical formulas are derived for the effective radial force acting on the beam ions, which can be used to minimize beam pinching. The results of analytic theory have been verified by comparison with the simulation results obtained from two particle-in-cell codes, which show good agreement.

  2. Measurement of Neutral Current Neutral Pion Production on Carbon in a Few-GeV Neutrino Beam

    SciTech Connect

    Kurimoto, Yoshinori

    2010-01-01

    Understanding of the π0 production via neutrino-nucleus neutral current interaction in the neutrino energy region of a few GeV is essential for the neutrino oscillation experiments. In this thesis, we present a study of neutral current π0 production from muon neutrinos scattering on a polystyrene (C8H8) target in the SciBooNE experiment. All neutrino beam data corresponding to 0.99 × 1020 protons on target have been analyzed. We have measured the cross section ratio of the neutral current π0 production to the total charge current interaction and the π0 kinematic distribution such as momentum and direction. We obtain [7.7 ± 0.5(stat.) ± 0.5(sys.)] × 10-2 as the ratio of the neutral current neutral pion production to total charged current cross section; the mean energy of neutrinos producing detected neutral pions is 1.1 GeV. The result agrees with the Rein- Sehgal model, which is generally used for the Monte Carlo simulation by many neutrino oscillation experiments. We achieve less than 10 % uncertainty which is required for the next generation search for νµ → νe oscillation. The spectrum shape of the π0 momentum and the distribution of the π0 emitted angle agree with the prediction, which means that not only the Rein-Sehgal model but also the intra-nuclear interaction models describe our data well. We also measure the ratio of the neutral current coherent pion production to total charged current cross section to be (1.17 ± 0.23 ) × 10-2 based on the Rein and Sehgal model. The result gives the evidence for non-zero coherent pion production via neutral current interaction at the mean neutrino energy of 1.0 GeV.

  3. Total neutrino and antineutrino charged current cross section measurements in 100, 160, and 200 GeV narrow band beams

    NASA Astrophysics Data System (ADS)

    Berge, P.; Blondel, A.; Böckmann, P.; Burkhardt, H.; Dydak, F.; de Groot, J. G. H.; Grant, A. L.; Hagelberg, R.; Hughes, E. W.; Krasny, M.; Meyer, H. J.; Palazzi, P.; Ranjard, F.; Rothberg, J.; Steinberger, J.; Taureg, H.; Wachsmuth, H.; Wahl, H.; Williams, R. W.; Wotschack, J.; Wysłouch, B.; Blümer, H.; Brummel, H. D.; Buchholz, P.; Duda, J.; Eisele, F.; Kampschulte, B.; Kleinknecht, K.; Knobloch, J.; Müller, E.; Pszola, B.; Renk, B.; Belusević, R.; Falkenburg, B.; Fiedler, M.; Geiges, R.; Geweniger, C.; Hepp, V.; Keilwerth, H.; Kurz, N.; Tittel, K.; Debu, P.; Guyot, C.; Merlo, J. P.; Para, A.; Perez, P.; Perrier, F.; Rander, J.; Schuller, J. P.; Turlay, R.; Vallage, B.; Abramowicz, H.; Królikowski, J.; Lipniacka, A.

    1987-12-01

    Neutrino and antineutrino total charged current cross sections on iron were measured in the 100, 160, and 200 GeV narrow band beams at the CERN SPS in the energy range 10 to 200 GeV. Assuming σ/ E to be constant, the values corrected for non-isoscalarity are σv/E = (0.686 ± 0.019) * 10-38 cm2/ (GeV · nucleon) and σv/E = (0.339 ± 0.010) * 10-38 cm2/ (GeV·nucleon). Between 50 and 150 GeV no energy dependence of σ/ E was observed within ±3% for neutrino and ±4% for antineutrino interactions.

  4. Imaging interfacial electrical transport in graphene–MoS{sub 2} heterostructures with electron-beam-induced-currents

    SciTech Connect

    White, E. R. Kerelsky, Alexander; Hubbard, William A.; Regan, B. C.; Dhall, Rohan; Cronin, Stephen B.; Mecklenburg, Matthew

    2015-11-30

    Heterostructure devices with specific and extraordinary properties can be fabricated by stacking two-dimensional crystals. Cleanliness at the inter-crystal interfaces within a heterostructure is crucial for maximizing device performance. However, because these interfaces are buried, characterizing their impact on device function is challenging. Here, we show that electron-beam induced current (EBIC) mapping can be used to image interfacial contamination and to characterize the quality of buried heterostructure interfaces with nanometer-scale spatial resolution. We applied EBIC and photocurrent imaging to map photo-sensitive graphene-MoS{sub 2} heterostructures. The EBIC maps, together with concurrently acquired scanning transmission electron microscopy images, reveal how a device's photocurrent collection efficiency is adversely affected by nanoscale debris invisible to optical-resolution photocurrent mapping.

  5. Imaging interfacial electrical transport in graphene-MoS2 heterostructures with electron-beam-induced-currents

    NASA Astrophysics Data System (ADS)

    White, E. R.; Kerelsky, Alexander; Hubbard, William A.; Dhall, Rohan; Cronin, Stephen B.; Mecklenburg, Matthew; Regan, B. C.

    2015-11-01

    Heterostructure devices with specific and extraordinary properties can be fabricated by stacking two-dimensional crystals. Cleanliness at the inter-crystal interfaces within a heterostructure is crucial for maximizing device performance. However, because these interfaces are buried, characterizing their impact on device function is challenging. Here, we show that electron-beam induced current (EBIC) mapping can be used to image interfacial contamination and to characterize the quality of buried heterostructure interfaces with nanometer-scale spatial resolution. We applied EBIC and photocurrent imaging to map photo-sensitive graphene-MoS2 heterostructures. The EBIC maps, together with concurrently acquired scanning transmission electron microscopy images, reveal how a device's photocurrent collection efficiency is adversely affected by nanoscale debris invisible to optical-resolution photocurrent mapping.

  6. EBIC (electron beam induced current) contrast of clean, decorated and deuterium passivated Si(Ge) epitaxial misfit dislocations

    SciTech Connect

    Zhou, T.Q.; Buczkowski, A.; Radzimski, Z.J.; Rozgonyi, G.A. . Dept. of Materials Science and Engineering); Seager, C.H.; Panitz, J. )

    1991-01-01

    The electrical activity of as-grown and intentionally decorated misfit dislocations in an epitaxial Si/Si(Ge) heterostructure was examined using the electron beam induced current (EBIC) technique in a scanning electron microscope. Misfit dislocations, which were not visible initially, were subsequently activated either by an unknown processing contaminant or a backside metallic impurity. Passivation of these contaminated dislocations was then studied using low energy deuterium ion implantation in a Kaufman ion source. EBIC results show that the recombination activity of the decorated misfit dislocations was dramatically reduced by the deuterium treatment. Although a front side passivation treatment was more effective than a backside treatment, a surface ion bombardment damage problem is still evident. 5 refs., 3 figs.

  7. Influence of electron-beam lithography exposure current level on the transport characteristics of graphene field effect transistors

    NASA Astrophysics Data System (ADS)

    Kang, Sangwoo; Movva, Hema C. P.; Sanne, Atresh; Rai, Amritesh; Banerjee, Sanjay K.

    2016-03-01

    Many factors have been identified to influence the electrical transport characteristics of graphene field-effect transistors. In this report, we examine the influence of the exposure current level used during electron beam lithography (EBL) for active region patterning. In the presence of a self-assembled hydrophobic residual layer generated by oxygen plasma etching covering the top surface of the graphene channel, we show that the use of low EBL current level results in higher mobility, lower residual carrier density, and charge neutrality point closer to 0 V, with reduced device-to-device variations. We show that this correlation originates from the resist heating dependent release of radicals from the resist material, near its interface with graphene, and its subsequent trapping by the hydrophobic polymer layer. Using a general model for resist heating, we calculate the difference in resist heating for different EBL current levels. We further corroborate our argument through control experiments, where radicals are either intentionally added or removed by other processes. We also utilize this finding to obtain mobilities in excess of 18 000 cm2/V s on silicon dioxide substrates. We believe these results are applicable to other 2D materials such as transition metal dichalcogenides and nanoscale devices in general.

  8. Relativistic high-current electron-beam stopping-power characterization in solids and plasmas: collisional versus resistive effects.

    PubMed

    Vauzour, B; Santos, J J; Debayle, A; Hulin, S; Schlenvoigt, H-P; Vaisseau, X; Batani, D; Baton, S D; Honrubia, J J; Nicolaï, Ph; Beg, F N; Benocci, R; Chawla, S; Coury, M; Dorchies, F; Fourment, C; d'Humières, E; Jarrot, L C; McKenna, P; Rhee, Y J; Tikhonchuk, V T; Volpe, L; Yahia, V

    2012-12-21

    We present experimental and numerical results on intense-laser-pulse-produced fast electron beams transport through aluminum samples, either solid or compressed and heated by laser-induced planar shock propagation. Thanks to absolute K(α) yield measurements and its very good agreement with results from numerical simulations, we quantify the collisional and resistive fast electron stopping powers: for electron current densities of ≈ 8 × 10(10) A/cm(2) they reach 1.5 keV/μm and 0.8 keV/μm, respectively. For higher current densities up to 10(12)A/cm(2), numerical simulations show resistive and collisional energy losses at comparable levels. Analytical estimations predict the resistive stopping power will be kept on the level of 1 keV/μm for electron current densities of 10(14)A/cm(2), representative of the full-scale conditions in the fast ignition of inertially confined fusion targets. PMID:23368474

  9. Current-induced spin polarization in transition metals and Bi/Ag bilayers observed by spin-polarized positron beam

    NASA Astrophysics Data System (ADS)

    Zhang, Hongjun; Yamamoto, Shunya; Fukaya, Yuki; Maekawa, Masaki; Li, Hui; Kawasuso, Atsuo; Seki, Takeshi; Saitoh, Eiji; Takanashi, Koki; JAEA Team; Tohoku Team

    2015-03-01

    Current-induced spin polarization (CISP) on the outermost surfaces of Au, Cu, Pt, Pd, Ta, and W films were studied by spin-polarized positron beam (SPPB). The Au and Cu surfaces showed no significant CISP. In contrast, the Pt, Pd, Ta, and W films exhibited large CISP (3 ~ 15% per charge current of 105 A/cm2) and the CISP of Ta and W were opposite to those of Pt and Pd. The sign of the CISP obeys the same rule in spin Hall effect suggesting that the spin-orbit coupling is mainly responsible for the CISP. The outermost spin poalrization of Bi/Ag/Al2O3andAg/Bi/Al2O3 (charge currents directly connected to Ag layers) were probed by SPPB. The opposite outermost spin polarization of Bi/Ag/Al2O3andAg/Bi/Al2O3 clarified the charge-to-spin conversion in Bi/Ag bilayers. Nevertheless, the magnitudes of the outermost spin polarization of Bi(0.3 ~5)/Ag(25)/Al2O3 (numbers in parentheses denote thickness in nm) and Ag(25 ~500)/Bi(8)/Al2O3 decrease exponentially with increasing Bi thickness and Ag thickness, respectively. This provides probably the first direct evidence for spin diffusion mechanism. Financial support from JSPS Kakenhi Grant 24310072.

  10. Detection and characterization of stacking faults by light beam induced current mapping and scanning infrared microscopy in silicon

    NASA Astrophysics Data System (ADS)

    Vève-Fossati, C.; Martinuzzi, S.

    1998-08-01

    Non destructive techniques like scanning infrared microscopy and light beam induced current mapping are used to reveal the presence of stacking faults in heat treated Czochralski grown silicon wafers. In oxidized or contaminated samples, scanning infrared microscopy reveals that stacking faults grow around oxygen precipitates. This could be due to an aggregation of silicon self-interstitials emitted by the growing precipitates in the (111) plane. Light beam induced current maps show that the dislocations which surround the stacking faults are the main source of recombination centers, especially when they are decorated by a fast diffuser like copper. Des techniques non destructives telles que la microscopie infrarouge à balayage et la cartographie de photocourant induit par un spot lumineux ont été utilisées pour révéler la présence de fautes d'empilement après traitements thermiques, dans des plaquettes de silicium préparées par tirage Czochralski. Dans des échantillons oxydés ou contaminés, la microscopie infrarouge à balayage révèle des fautes d'empilement qui se développent autour des précipités d'oxygène. Cela peut être dû à la formation d'un agglomérat d'auto-interstitiels de silicium émis par la croissance des précipités dans les plans (111). Les cartographies de photocourant montrent que les dislocations qui entourent les fautes d'empilement sont la principale source de centres de recombinaison, et cela tout particulièrement quand ces fautes sont décorées par un diffuseur rapide tel que le cuivre.

  11. Dosimetric properties of high energy current (HEC) detector in keV x-ray beams.

    PubMed

    Zygmanski, Piotr; Shrestha, Suman; Elshahat, Bassem; Karellas, Andrew; Sajo, Erno

    2015-04-01

    We introduce a new x-ray radiation detector. The detector employs high-energy current (HEC) formed by secondary electrons consisting predominantly of photoelectrons and Auger electrons, to directly convert x-ray energy to detector signal without externally applied power and without amplification. The HEC detector is a multilayer structure composed of thin conducting layers separated by dielectric layers with an overall thickness of less than a millimeter. It can be cut to any size and shape, formed into curvilinear surfaces, and thus can be designed for a variety of QA applications. We present basic dosimetric properties of the detector as function of x-ray energy, depth in the medium, area and aspect ratio of the detector, as well as other parameters. The prototype detectors show similar dosimetric properties to those of a thimble ionization chamber, which operates at high voltage. The initial results obtained for kilovoltage x-rays merit further research and development towards specific medical applications. PMID:25789488

  12. Harmonics generation of a terahertz wakefield free-electron laser from a dielectric loaded waveguide excited by a direct current electron beam.

    PubMed

    Li, Weiwei; Lu, Yalin; He, Zhigang; Jia, Qika; Wang, Lin

    2016-06-01

    We propose to generate high-power terahertz (THz) radiation from a cylindrical dielectric loaded waveguide (DLW) excited by a direct-current electron beam with the harmonics generation method. The DLW supports a discrete set of modes that can be excited by an electron beam passing through the structure. The interaction of these modes with the co-propagating electron beam results in micro-bunching and the coherent enhancement of the wakefield radiation, which is dominated by the fundamental mode. By properly choosing the parameters of DLW and beam energy, the high order modes can be the harmonics of the fundamental one; thus, high frequency radiation corresponding to the high order modes will benefit from the dominating bunching process at the fundamental eigenfrequency and can also be coherently excited. With the proposed method, high power THz radiation can be obtained with an easily achievable electron beam and a large DLW structure. PMID:27244388

  13. A Measurement of Neutrino Charged Current Interactions and a Search for Muon Neutrino Disappearance with the Fermilab Booster Neutrino Beam

    SciTech Connect

    Nakajima, Yasuhiro

    2011-01-01

    In this thesis, we report on a measurement of muon neutrino inclusive charged current interactions on carbon in the few GeV region, using the Fermilab Booster Neutrino Beam. The all neutrino mode data collected in the SciBooNE experiment is used for this analysis. We collected high-statistics CC interaction sample at SciBooNE, and extracted energy dependent inclusive charged current interaction rates and cross sections for a wide energy range from 0.25 GeV to ~3 GeV. We measure the interaction rates with 6-15% precision, and the cross sections with 10-30% precision. We also made an energy integrated measurements, with the precisions of 3% for the rate, and 8% for the cross section measurements. This is the first measurement of the CC inclusive cross section on carbon around 1 GeV. This inclusive interaction measurement is nearly free from effects of hadron re-interactions in the nucleus. Hence, it is complementary to other exclusive cross section measurements, and essential to understand the neutrino interaction cross sections in the few GeV region, which is relevant to ongoing and future neutrino oscillation experiments. This analysis also provides the normalization for SciBooNE's previous cross section ratio measurements for charged current coherent pion production and neutral current neutral pion production. Then, a precise comparison between our previous measurements and the model predictions becomes possible. The result of the interaction rate measurement is used to constrain the product of the neutrino flux and the cross section at the other experiment on the Fermilab Booster Neutrino Beam: Mini-BooNE. We conducted a search for short-baseline muon neutrino disappearance using data both from SciBooNE and MiniBooNE, to test a possible neutrino oscillation with sterile neutrinos which is suggested by the LSND experiment. With this constraint by SciBooNE, we significantly reduced the flux and the cross section uncertainties at MiniBooNE, and achieved the world

  14. Generation and control of a powerful electron-beam current in an accelerator based on a secondary-emission source and its application

    NASA Astrophysics Data System (ADS)

    Aizatsky, N. I.; Dovbnya, A. N.; Zakutin, V. V.; Reshetnyak, N. G.; Romas'ko, V. P.; Chertishchev, I. A.; Boriskin, V. N.; Dovbnya, N. A.

    2014-09-01

    An electron accelerator in which magnetron guns with secondary-emission cathodes of two types are used as a particle source is described. The electron-beam parameters are investigated in an electron energy range of 20-150 keV at a pulse length of 10-50 μs. Results of target irradiation by an electron beam are represented. The target surface structure is studied by the metallographic method, and the microhardness and strength of zirconium materials are measured. The possibility of beam current control by factors of 2.5-3.5 with various methods is shown.

  15. Neutralization of space charge on high-current low-energy ion beam by low-energy electrons supplied from silicon based field emitter arrays

    SciTech Connect

    Gotoh, Yasuhito; Tsuji, Hiroshi; Taguchi, Shuhei; Ikeda, Keita; Kitagawa, Takayuki; Ishikawa, Junzo; Sakai, Shigeki

    2012-11-06

    Neutralization of space charge on a high-current and low-energy ion beam was attempted to reduce the divergence with an aid of low-energy electrons supplied from silicon based field emitter arrays (Si-FEAs). An argon ion beam with the energy of 500 eV and the current of 0.25 mA was produced by a microwave ion source. The initial beam divergence and the emittance were measured at the entrance of the analysis chamber in order to estimate the intrinsic factors for beam divergence. The current density distribution of the beam after transport of 730 mm was measured by a movable Faraday cup, with and without electron supply from Si-FEAs. A similar experiment was performed with tungsten filaments as an electron source. The results indicated that the electron supply from FEA had almost the same effect as the thermionic filament, and it was confirmed that both electron sources can neutralize the ion beam.

  16. Multi-dimensional collective effects in high-current relativistic beams relevant to High Density Laboratory Plasmas

    SciTech Connect

    Shvets, Gennady

    2014-05-09

    In summary, an analytical model describing the self-pinching of a relativistic charge-neutralized electron beam undergoing the collisionless Weibel instability in an overdense plasma has been developed. The model accurately predicts the final temperature and size of the self-focused filament. It is found that the final temperature is primarily defined by the total beam’s current, while the filament’s radius is shown to be smaller than the collisionless skin depth in the plasma and primarily determined by the beam’s initial size. The model also accurately predicts the repartitioning ratio of the initial energy of the beam’s forward motion into the magnetic field energy and the kinetic energy of the surrounding plasma. The density profile of the final filament is shown to be a superposition of the standard Bennett pinch profile and a wide halo surrounding the pinch, which contains a significant fraction of the beam’s electrons. PIC simulations confirm the key assumption of the analytic theory: the collisionless merger of multiple current filaments in the course of the Weibel Instability provides the mechanism for Maxwellization of the beam’s distribution function. Deviations from the Maxwell-Boltzmann distribution are explained by incomplete thermalization of the deeply trapped and halo electrons. It is conjectured that the simple expression derived here can be used for understanding collsionless shock acceleration and magnetic field amplification in astrophysical plasmas.

  17. Compact antenna for two-dimensional beam scan in the JT-60U electron cyclotron heating/current drive system

    SciTech Connect

    Moriyama, S.; Kajiwara, K.; Takahashi, K.; Kasugai, A.; Seki, M.; Ikeda, Y.; Fujii, T.

    2005-11-15

    A compact antenna system was designed and fabricated to enable millimeter-wave beam scanning in the toroidal and poloidal directions of the JT-60U tokamak for electron cyclotron heating (ECH) and electron cyclotron current drive (ECCD) experiments. The antenna consists of a fast movable flat mirror mounted on the tokamak vacuum vessel and a rotary focusing mirror attached at the end of the waveguide that is supported from outside the vacuum vessel. This separate support concept enables a compact structure inside a shallow port (0.68x0.54x0.2 m) that is shared with a subport for an independent diagnostic system. During a plasma shot, the flat mirror is driven by a servomotor with a 3-m-long drive shaft to reduce the influence of the high magnetic field on the motor. The focusing mirror is rotated by a simple mechanism utilizing a push rod and an air cylinder. The antenna has been operated reliably for 3 years after a small improvement to the rotary drive mechanism. It has made significant contributions to ECH and ECCD experiments, especially the current profile control in JT-60U.

  18. SUPPLEMENTARY COMPARISON: Final report EUROMET.EM-S11 on EUROMET Projects 473 and 612: Comparison of the measurement of current transformers (CTs)

    NASA Astrophysics Data System (ADS)

    Harmon, Stuart; Henderson, Lesley

    2009-01-01

    The Euromet comparison entitled 'Comparison of the measurement of current transformers' was carried out over two projects with NPL as pilot laboratory and thirteen other participating European National Measurement Institutes (NMI). Current transformer measurements made by the participating NMIs support a large number of measurements made in the electrical generation, supply and distribution industries in their own countries. They also support many transformer manufacturers who rely on national standards as a source of traceability. The current (ratio) errors and phase displacement of each ratio of the uncompensated current transformer transfer standard were determined at a defined frequency, burden and power factor, using each participant's standard measuring method and equipment. The results supplied by each participant generally show good agreement but with a few exceptions over the whole range of measured values. Deviations from the comparison reference value were mostly within the quoted uncertainties, but again with a few exceptions. A summary of outlying results compared to laboratories' declared Calibration and Measurement Capabilities (CMC) is given in the conclusion. In several cases participants have been making current transformer measurements with new measurement systems and techniques, and in one case for the first time; therefore a large amount of experience in the measurement and interpretation of results has been obtained from this comparison. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

  19. RAPID COMMUNICATION: Large improvement in high-field critical current densities of Nb3Al conductors by the transformation-heat-based up-quenching method

    NASA Astrophysics Data System (ADS)

    Takeuchi, T.; Banno, N.; Fukuzaki, T.; Wada, H.

    2000-10-01

    The bcc supersaturated solid solution Nb(Al)ss obtained by rapid heating and quenching of a multifilamentary Nb/Al composite wire has shown a crystal structure change from a disordered to an ordered structure before transforming to the A15 Nb3Al phase. Such ordering of the bcc phase seems to be responsible for the A15 phase stacking faults that depress the critical temperature (Tc), the upper critical magnetic field (Bc2) and, hence, the critical current density (Jc) of Nb3Al in high fields. A heat treatment around 1000 °C, higher than conventional transformation temperatures by about 200 °C, suppresses the ordering and yields a new phenomenon termed the `transformation-heat-based up-quenching' (TRUQ). TRUQ is characterized by the self-heating of the bcc phase by the transformation heat, which propagates through the whole length of a composite wire and transforms it to Nb3Al. A subsequent annealing at 800 °C enhances the long-range ordering of the Nb3Al phase and drastically improves the high-field critical current densities of the Nb3Al conductors.

  20. Magnetron sputtering system for coatings deposition with activation of working gas mixture by low-energy high-current electron beam

    NASA Astrophysics Data System (ADS)

    Gavrilov, N. V.; Kamenetskikh, A. S.; Men'shakov, A. I.; Bureyev, O. A.

    2015-11-01

    For the purposes of efficient decomposition and ionization of the gaseous mixtures in a system for coatings deposition using reactive magnetron sputtering, a low-energy (100-200 eV) high-current electron beam is generated by a grid-stabilized plasma electron source. The electron source utilizes both continuous (up to 20 A) and pulse-periodic mode of discharge with a self-heated hollow cathode (10-100 A; 0.2 ms; 10-1000 Hz). The conditions for initiation and stable burning of the high-current pulse discharge are studied along with the stable generation of a low-energy electron beam within the gas pressure range of 0.01 - 1 Pa. It is shown that the use of the electron beam with controllable parameters results in reduction of the threshold values both for the pressure of gaseous mixture and for the fluxes of molecular gases. Using such a beam also provides a wide range (0.1-10) of the flux density ratios of ions and sputtered atoms over the coating surface, enables an increase in the maximum pulse density of ion current from plasma up to 0.1 A, ensures an excellent adhesion, optimizes the coating structure, and imparts improved properties to the superhard nanocomposite coatings of (Ti,Al)N/a-Si3N4 and TiC/-a-C:H. Mass-spectrometric measurements of the beam-generated plasma composition proved to demonstrate a twofold increase in the average concentration of N+ ions in the Ar-N2 plasma generated by the high-current (100 A) pulsed electron beam, as compared to the dc electron beam.

  1. Electrostatic solitary waves in current layers: from Cluster observations during a super-substorm to beam experiments at the LAPD

    NASA Astrophysics Data System (ADS)

    Pickett, J. S.; Chen, L.-J.; Santolík, O.; Grimald, S.; Lavraud, B.; Verkhoglyadova, O. P.; Tsurutani, B. T.; Lefebvre, B.; Fazakerley, A.; Lakhina, G. S.; Ghosh, S. S.; Grison, B.; Décréau, P. M. E.; Gurnett, D. A.; Torbert, R.; Cornilleau-Wehrlin, N.; Dandouras, I.; Lucek, E.

    2009-06-01

    Electrostatic Solitary Waves (ESWs) have been observed by several spacecraft in the current layers of Earth's magnetosphere since 1982. ESWs are manifested as isolated pulses (one wave period) in the high time resolution waveform data obtained on these spacecraft. They are thus nonlinear structures generated out of nonlinear instabilities and processes. We report the first observations of ESWs associated with the onset of a super-substorm that occurred on 24 August 2005 while the Cluster spacecraft were located in the magnetotail at around 18-19 RE and moving northward from the plasma sheet to the lobes. These ESWs were detected in the waveform data of the WBD plasma wave receiver on three of the Cluster spacecraft. The majority of the ESWs were detected about 5 min after the super-substorm onset during which time 1) the PEACE electron instrument detected significant field-aligned electron fluxes from a few 100 eV to 3.5 keV, 2) the EDI instrument detected bursts of field-aligned electron currents, 3) the FGM instrument detected substantial magnetic fluctuations and the presence of Alfvén waves, 4) the STAFF experiment detected broadband electric and magnetic waves, ion cyclotron waves and whistler mode waves, and 5) CIS detected nearly comparable densities of H+ and O+ ions and a large tailward H+ velocity. We compare the characteristics of the ESWs observed during this event to those created in the laboratory at the University of California-Los Angeles Plasma Device (LAPD) with an electron beam. We find that the time durations of both space and LAPD ESWs are only slightly larger than the respective local electron plasma periods, indicating that electron, and not ion, dynamics are responsible for generation of the ESWs. We have discussed possible mechanisms for generating the ESWs in space, including the beam and kinetic Buneman type instabilities and the acoustic instabilities. Future studies will examine these mechanisms in more detail using the space

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

    SciTech Connect

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

    2006-08-07

    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{sub L}/L{sub n}, where d{sub L} is the laser beam diameter and L{sub n} is the plasma density gradient scale length. When d{sub L}>>L{sub n}, a dense highly collimated megaampere ion (proton) beam of the ion current density approaching TA/cm{sup 2} can be generated by skin-layer ponderomotive acceleration, even with a tabletop subpicosecond laser.

  3. A Study of Charged Current Single Charged Pion Productions on Carbon in a Few-GeV Neutrino Beam

    SciTech Connect

    Hiraide, Katsuki

    2009-01-01

    Understanding single charged pion production via neutrino-nucleus charged current interaction in the neutrino energy region of a few GeV is essential for future neutrino oscillation experiments since this process is a dominant background for vμ → vx oscillation measurements. There are two contributions to this process: single pion production via baryonic resonance (vμN → μ-+) and coherent pion production interacting with the entire nucleus (vμA → μ-+), where N is nucleon in the nucleus and A is the nucleus. The purpose of the study presented in this thesis is a precise measurement of charged current single charged pion productions, resonant and coherent pion productions, with a good final state separation in the neutrino energy region of a few GeV. In this thesis, we focus on the study of charged current coherent pion production from muon neutrinos scattering on carbon, vμ 12C → μ-12+, in the SciBooNE experiment. This is motivated by the fact that without measuring this component first, the precise determination of resonant pion production cross section can not be achieved since the contribution of coherent pion production in the region of small muon scattering angle is not small. Furthermore, the coherent process is particularly interesting because it is deeply rooted in fundamental physics via Adler's partially conserved axial-vector current theorem. We took data from June 2007 until August 2008, in both the neutrino and antineutrino beam. In total, 2.52 x 1020 protons on target were collected. We have performed a search for charged current coherent pion production by using SciBooNE's full neutrino data set, corresponding to 0.99 x 1020 protons on target. No evidence for coherent pion production is observed. We set 90% confidence level upper limits on the cross section ratio of charged

  4. Investigations on residual strains and the cathodoluminescence and electron beam induced current signal of grain boundaries in silicon

    SciTech Connect

    Nacke, M.; Allardt, M.; Hieckmann, E.; Weber, J.; Chekhonin, P.; Skrotzki, W.

    2014-04-28

    Cathodoluminescence (CL) and electron beam induced current (EBIC) measurements were used to investigate the optical behavior and electrical activity of grain boundaries (GBs) in coarsely grained silicon. Electron backscatter diffraction (EBSD) was applied for a comprehensive characterization of the structural properties of the high angle and low angle GBs (HAGBs and LAGBs) in the sample. It was found that not only the EBIC but also the panchromatic (pan) CL contrast of Σ3 HAGBs strongly depends on the hkl-type of the boundary plane. At room temperature coherent Σ3 GBs exhibit no significant contrast in the CL or EBIC images, whereas at low temperatures the pan-CL contrast is strong. For incoherent Σ3 GBs, a strong pan-CL and EBIC contrast was observed in the entire temperature range. Only on a LAGB (misorientation angle 4.5°) CL investigations at low temperatures revealed a line with peak position at about (0.82 ± 0.01) eV, usually related to the dislocation associated D1 transition. Cross-correlation EBSD was applied to analyze the strain fields of Σ3 HAGBs as well as of the LAGB. All the components of the local strain tensors were quantitatively determined. The relationship between the extension of the strain field at the LAGB and the spatial D1 intensity distribution is discussed.

  5. Surface Treatment of Polymers by Ion Beam Irradiation to Control the Human Osteoblast Adhesion: Fluence and Current Density Study

    NASA Astrophysics Data System (ADS)

    Guibert, G.; Rossel, T.; Weder, G.; Betschart, B.; Meunier, C.; Mikhailov, S.

    2009-03-01

    In the biomaterial field, the modification of surfaces are used to create polymers with high performances, preserving their bulk properties and creating specific interactions between the designed surfaces and the cells or tissues. The polymers were irradiated with a 900 keV Helium beam to modify their surface properties. Cell cultivation on the samples was done using human osteoblasts cells (hFOB 1.19). For PTFE, PS and PEEK polymers, the cell adhesion occurs after reached some threshold values of fluences. For PET or PMMA polymers, the cells adhere on the non irradiated samples, however the fluence value modifies the cell density. For PMMA and PTFE both, the fluence and the current density influence the cell adhesion. By modifying the appropriate parameters on each material, the control of the cell adhesion is possible. Indeed the surface treatment must be selected and adapted according to the further application: for biosensors, tissue engineering, tissue regeneration, neural probes, drug delivery, bio-actuators etc.

  6. Effect of chlorine activation treatment on electron beam induced current signal distribution of cadmium telluride thin film solar cells

    NASA Astrophysics Data System (ADS)

    Zywitzki, Olaf; Modes, Thomas; Morgner, Henry; Metzner, Christoph; Siepchen, Bastian; Späth, Bettina; Drost, Christian; Krishnakumar, Velappan; Frauenstein, Sven

    2013-10-01

    We have investigated CdTe thin film solar cells without activation treatment and with CdCl2 activation treatment at temperatures between 370 and 430 °C using a constant activation time of 25 min. For this purpose, CdS/CdTe layers were deposited by closed-space-sublimation on FTO coated float glass. The solar cells were characterized by measurements of the JV characteristics and quantum efficiencies. In addition, ion polished cross sections of the solar cells were prepared for high-resolution FE-SEM imaging of the microstructure and the simultaneous registration of electron beam induced current (EBIC) signal distribution. By measurement of the EBIC signal distribution, it can be shown that without activation treatment the CdTe grain boundaries itself and grain boundary near regions exhibit no EBIC signal, whereas centres of some singular grains already show a distinct EBIC signal. In contrast, after the chlorine activation treatment, the grain boundary near regions exhibit a significant higher EBIC signal than the centre of the grains. The results can be discussed as a direct evidence for defect passivation of grain boundary near regions by the chlorine activation treatment. At activation temperature of 430 °C, additionally, a significant grain growth and agglomeration of the CdS layer can be recognized, which is linked with the formation of voids within the CdS layer and a deterioration of pn junction properties.

  7. Surface Treatment of Polymers by Ion Beam Irradiation to Control the Human Osteoblast Adhesion: Fluence and Current Density Study

    SciTech Connect

    Guibert, G.; Mikhailov, S.; Rossel, T.; Weder, G.; Betschart, B.; Meunier, C.

    2009-03-10

    In the biomaterial field, the modification of surfaces are used to create polymers with high performances, preserving their bulk properties and creating specific interactions between the designed surfaces and the cells or tissues. The polymers were irradiated with a 900 keV Helium beam to modify their surface properties. Cell cultivation on the samples was done using human osteoblasts cells (hFOB 1.19). For PTFE, PS and PEEK polymers, the cell adhesion occurs after reached some threshold values of fluences. For PET or PMMA polymers, the cells adhere on the non irradiated samples, however the fluence value modifies the cell density. For PMMA and PTFE both, the fluence and the current density influence the cell adhesion. By modifying the appropriate parameters on each material, the control of the cell adhesion is possible. Indeed the surface treatment must be selected and adapted according to the further application: for biosensors, tissue engineering, tissue regeneration, neural probes, drug delivery, bio-actuators etc.

  8. Current external beam radiation therapy quality assurance guidance: does it meet the challenges of emerging image-guided technologies?

    PubMed

    Palta, Jatinder R; Liu, Chihray; Li, Jonathan G

    2008-01-01

    The traditional prescriptive quality assurance (QA) programs that attempt to ensure the safety and reliability of traditional external beam radiation therapy are limited in their applicability to such advanced radiation therapy techniques as three-dimensional conformal radiation therapy, intensity-modulated radiation therapy, inverse treatment planning, stereotactic radiosurgery/radiotherapy, and image-guided radiation therapy. The conventional QA paradigm, illustrated by the American Association of Physicists in Medicine Radiation Therapy Committee Task Group 40 (TG-40) report, consists of developing a consensus menu of tests and device performance specifications from a generic process model that is assumed to apply to all clinical applications of the device. The complexity, variation in practice patterns, and level of automation of high-technology radiotherapy renders this "one-size-fits-all" prescriptive QA paradigm ineffective or cost prohibitive if the high-probability error pathways of all possible clinical applications of the device are to be covered. The current approaches to developing comprehensive prescriptive QA protocols can be prohibitively time consuming and cost ineffective and may sometimes fail to adequately safeguard patients. It therefore is important to evaluate more formal error mitigation and process analysis methods of industrial engineering to more optimally focus available QA resources on process components that have a significant likelihood of compromising patient safety or treatment outcomes. PMID:18406911

  9. Spatially resolved imaging of charge collection efficiency in polycrystalline CVD diamond by the use of ion beam induced current

    NASA Astrophysics Data System (ADS)

    Beckmann, D. R.; Saint, A.; Gonon, P.; Jamieson, D. N.; Prawer, S.; Kalish, R.

    1997-07-01

    Diamond based detectors have potential applications in high energy physics experiments. These detectors can be fabricated from synthetic Chemical Vapour Deposited (CVD) polycrystalline diamond films. Previously it has been shown by the Turin group and their coworkers in Zagreb that it is possible to investigate the electrical characteristics of high quality polycrystalline CVD diamond films by Ion Beam Induced Current (IBIC). The present work describes IBIC images obtained using 2 MeV He + irradiation of 250 μm thick polycrystalline diamond films through a thin gold surface contact layer biased positively relative to the grounded rear surface of the film. In contrast to previous experiments the present spectra of collected charge display a clearly defined peak from the induced charge. Images obtained by separating these spectra into different regions of interest allow the identification of regions in the sample of different charge collection efficiency. In particular the presence of some grains in which no charge collection appears possible and the reduction in charge collection efficiency at the grain boundaries is evident.

  10. Temperature-dependent recombination velocity analysis on artificial small angle grain boundaries using electron beam induced current method

    NASA Astrophysics Data System (ADS)

    Kojima, Takuto; Tachibana, Tomihisa; Ohshita, Yoshio; Prakash, Ronit R.; Sekiguchi, Takashi; Yamaguchi, Masafumi

    2016-02-01

    The details of the process of carrier recombination via the Shockley-Read-Hall (SRH) defect level, at the grain boundaries of multicrystalline silicon, were investigated. For this, the temperature-dependent recombination velocities, as determined by experiments, were analyzed by the application of an electron beam induced current method. For the model, the misorientation angles at the grain boundaries were defined using a multi-seed casting-growth method. The results of our experiments indicated different temperature behaviors at low and high temperatures. These can be explained by controlling the process anticipated by the SRH model, that is, the process whereby minority carriers (electrons) are captured at lower temperatures, followed by the reemission of the carriers before recombination with Arrhenius behavior at higher temperatures. The minority capture process appeared to conform to the power law T-α temperature behavior. Thus, there are two candidate electron capture mechanisms, namely, cascade phonon emission capture for shallow centers and excitonic-Auger capture for deep centers. The activation energy for the reemission of carriers was around 0.1 eV. These findings regarding the temperature dependence are essentially independent of the misorientation angles, suggesting a common defect level and recombination mechanism. The difference in the recombination velocities can be regarded as being derived from the difference in the density at the defect level.

  11. Parametic Study of the current limit within a single driver-scaletransport beam line of an induction Linac for Heavy Ion Fusion

    SciTech Connect

    Prost, Lionel Robert

    2007-02-14

    The High Current Experiment (HCX) at Lawrence Berkeley National Laboratory is part of the US program that explores heavy-ion beam as the driver option for fusion energy production in an Inertial Fusion Energy (IFE) plant. The HCX is a beam transport experiment at a scale representative of the low-energy end of an induction linear accelerator driver. The primary mission of this experiment is to investigate aperture fill factors acceptable for the transport of space-charge-dominated heavy-ion beams at high intensity (line charge density {approx}0.2 {micro}C/m) over long pulse durations (4 {micro}s) in alternating gradient focusing lattices of electrostatic or magnetic quadrupoles. This experiment is testing transport issues resulting from nonlinear space-charge effects and collective modes, beam centroid alignment and steering, envelope matching, image charges and focusing field nonlinearities, halo and, electron and gas cloud effects. We present the results for a coasting 1 MeV K{sup +} ion beam transported through ten electrostatic quadrupoles. The measurements cover two different fill factor studies (60% and 80% of the clear aperture radius) for which the transverse phase-space of the beam was characterized in detail, along with beam energy measurements and the first halo measurements. Electrostatic quadrupole transport at high beam fill factor ({approx}80%) is achieved with acceptable emittance growth and beam loss. We achieved good envelope control, and re-matching may only be needed every ten lattice periods (at 80% fill factor) in a longer lattice of similar design. We also show that understanding and controlling the time dependence of the envelope parameters is critical to achieving high fill factors, notably because of the injector and matching section dynamics.

  12. TH-E-BRE-09: TrueBeam Monte Carlo Absolute Dose Calculations Using Monitor Chamber Backscatter Simulations and Linac-Logged Target Current

    SciTech Connect

    A, Popescu I; Lobo, J; Sawkey, D; Svatos, M

    2014-06-15

    Purpose: To simulate and measure radiation backscattered into the monitor chamber of a TrueBeam linac; establish a rigorous framework for absolute dose calculations for TrueBeam Monte Carlo (MC) simulations through a novel approach, taking into account the backscattered radiation and the actual machine output during beam delivery; improve agreement between measured and simulated relative output factors. Methods: The ‘monitor backscatter factor’ is an essential ingredient of a well-established MC absolute dose formalism (the MC equivalent of the TG-51 protocol). This quantity was determined for the 6 MV, 6X FFF, and 10X FFF beams by two independent Methods: (1) MC simulations in the monitor chamber of the TrueBeam linac; (2) linac-generated beam record data for target current, logged for each beam delivery. Upper head MC simulations used a freelyavailable manufacturer-provided interface to a cloud-based platform, allowing use of the same head model as that used to generate the publicly-available TrueBeam phase spaces, without revealing the upper head design. The MC absolute dose formalism was expanded to allow direct use of target current data. Results: The relation between backscatter, number of electrons incident on the target for one monitor unit, and MC absolute dose was analyzed for open fields, as well as a jaw-tracking VMAT plan. The agreement between the two methods was better than 0.15%. It was demonstrated that the agreement between measured and simulated relative output factors improves across all field sizes when backscatter is taken into account. Conclusion: For the first time, simulated monitor chamber dose and measured target current for an actual TrueBeam linac were incorporated in the MC absolute dose formalism. In conjunction with the use of MC inputs generated from post-delivery trajectory-log files, the present method allows accurate MC dose calculations, without resorting to any of the simplifying assumptions previously made in the TrueBeam

  13. Revealing martensitic transformation and α/β interface evolution in electron beam melting three-dimensional-printed Ti-6Al-4V

    PubMed Central

    Tan, Xipeng; Kok, Yihong; Toh, Wei Quan; Tan, Yu Jun; Descoins, Marion; Mangelinck, Dominique; Tor, Shu Beng; Leong, Kah Fai; Chua, Chee Kai

    2016-01-01

    As an important metal three-dimensional printing technology, electron beam melting (EBM) is gaining increasing attention due to its huge potential applications in aerospace and biomedical fields. EBM processing of Ti-6Al-4V as well as its microstructure and mechanical properties were extensively investigated. However, it is still lack of quantitative studies regarding its microstructural evolution, indicative of EBM thermal process. Here, we report α′ martensitic transformation and α/β interface evolution in varied printing thicknesses of EBM-printed Ti-6Al-4V block samples by means of atom probe tomography. Quantitative chemical composition analysis suggests a general phase transformation sequence. By increasing in-fill hatched thickness, elemental partitioning ratios arise and β volume fraction is increased. Furthermore, we observe kinetic vanadium segregation and aluminum depletion at interface front and the resultant α/β interface widening phenomenon. It may give rise to an increased α/β lattice mismatch and weakened α/β interfaces, which could account for the degraded strength as printing thickness increases. PMID:27185285

  14. Revealing martensitic transformation and α/β interface evolution in electron beam melting three-dimensional-printed Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Tan, Xipeng; Kok, Yihong; Toh, Wei Quan; Tan, Yu Jun; Descoins, Marion; Mangelinck, Dominique; Tor, Shu Beng; Leong, Kah Fai; Chua, Chee Kai

    2016-05-01

    As an important metal three-dimensional printing technology, electron beam melting (EBM) is gaining increasing attention due to its huge potential applications in aerospace and biomedical fields. EBM processing of Ti-6Al-4V as well as its microstructure and mechanical properties were extensively investigated. However, it is still lack of quantitative studies regarding its microstructural evolution, indicative of EBM thermal process. Here, we report α‧ martensitic transformation and α/β interface evolution in varied printing thicknesses of EBM-printed Ti-6Al-4V block samples by means of atom probe tomography. Quantitative chemical composition analysis suggests a general phase transformation sequence. By increasing in-fill hatched thickness, elemental partitioning ratios arise and β volume fraction is increased. Furthermore, we observe kinetic vanadium segregation and aluminum depletion at interface front and the resultant α/β interface widening phenomenon. It may give rise to an increased α/β lattice mismatch and weakened α/β interfaces, which could account for the degraded strength as printing thickness increases.

  15. Revealing martensitic transformation and α/β interface evolution in electron beam melting three-dimensional-printed Ti-6Al-4V.

    PubMed

    Tan, Xipeng; Kok, Yihong; Toh, Wei Quan; Tan, Yu Jun; Descoins, Marion; Mangelinck, Dominique; Tor, Shu Beng; Leong, Kah Fai; Chua, Chee Kai

    2016-01-01

    As an important metal three-dimensional printing technology, electron beam melting (EBM) is gaining increasing attention due to its huge potential applications in aerospace and biomedical fields. EBM processing of Ti-6Al-4V as well as its microstructure and mechanical properties were extensively investigated. However, it is still lack of quantitative studies regarding its microstructural evolution, indicative of EBM thermal process. Here, we report α' martensitic transformation and α/β interface evolution in varied printing thicknesses of EBM-printed Ti-6Al-4V block samples by means of atom probe tomography. Quantitative chemical composition analysis suggests a general phase transformation sequence. By increasing in-fill hatched thickness, elemental partitioning ratios arise and β volume fraction is increased. Furthermore, we observe kinetic vanadium segregation and aluminum depletion at interface front and the resultant α/β interface widening phenomenon. It may give rise to an increased α/β lattice mismatch and weakened α/β interfaces, which could account for the degraded strength as printing thickness increases. PMID:27185285

  16. 20 Years History of Fundamental Research on Gas Cluster Ion Beams, and Current Status of the Applications to Industry

    NASA Astrophysics Data System (ADS)

    Yamada, Isao

    2006-11-01

    This paper reviews the development of gas cluster ion beam (GCIB) technology, including the generation of cluster beams, fundamental characteristics of cluster ion to solid surface interactions, emerging industrial applications, and identification of some of the significant events which occurred as the technology has evolved into what it is today. More than 20 years have passed since the author first began to explore feasibility of processing by gas cluster ion beams at the Ion Beam Engineering Experimental Laboratory of Kyoto University. Processes employing ions of gaseous material clusters comprised of a few hundred to many thousand atoms are now being developed into a new field of ion beam technology. Cluster-surface collisions produce important non-linear effects which are being applied to shallow junction formation, to etching and smoothing of semiconductors, metals, and dielectrics, to assisted formation of thin films with nano-scale accuracy, and to other surface modification applications.

  17. Effects of aging on the structural, mechanical, and thermal properties of the silicone rubber current transformer insulation bushing for a 500 kV substation.

    PubMed

    Wang, Zhigao; Zhang, Xinghai; Wang, Fangqiang; Lan, Xinsheng; Zhou, Yiqian

    2016-01-01

    In order to analyze the cracking and aging reason of the silicone rubber current transformer (CT) insulation bushing used for 8 years from a 500 kV alternating current substation, characteristics including Fourier transform infrared (FTIR) spectroscopy, mechanical properties analysis, hardness, and thermo gravimetric analysis have been carried out. The FTIR results indicated that the external surface of the silicone rubber CT insulation bushing suffered from more serious aging than the internal part, fracture of side chain Si-C bond was much more than the backbone. Mechanical properties and thermal stability results illustrated that the main aging reasons were the breakage of side chain Si-C bond and the excessive cross-linking reaction of the backbone. This study can provide valuable basis for evaluating degradation mechanism and aging state of the silicone rubber insulation bushing in electric power field. PMID:27390631

  18. The evaluation of surface recombination velocity from normal-collector geometry electron-beam-induced current line scans

    NASA Astrophysics Data System (ADS)

    Luke, Keung L.

    1994-02-01

    There are two well-known point source-based methods for the evaluation of the surface recombination velocity s from normal-collector geometry electron-beam-induced current (EBIC) line scans. The first was proposed by Jastrzebski, Lagowski, and Gatos [Appl. Phys. Lett. 27, 537 (1975)], the second was by Watanabe, Actor, and Gatos (WAG) [IEEE Trans. Electron Dev. ED-24, 1172 (1977)]. Scheer, Wilhelm, and Lewerenz [J. Appl. Phys. 66, 5412 (1989)] were unsuccessful in using the first method to extract s from their EBIC data. Hakimzadeh, Möller, and Bailey [J. Appl. Phys. 72, 2919 (1992)] applied the second method to evaluate s from their EBIC data without accounting for the mismatch between the theoretical requirement and the experimental condition relating to source size and electron penetration depth at which the WAG expression is to be evaluated. In this article these two methods are evaluated and their applicability to both point and extended-source data is examined quantitatively. Their limitations and shortcomings led us to suggest a way to extend the applicability of the WAG expression to include extended sources and to formulate two new Gaussian source-based methods to evaluate the surface recombination velocity. A number of computed curves are provided to facilitate the application of these proposed new methods to GaAs and other semiconductors with diffusion lengths in the range of 0.5-3.0 μm and (surface recombination velocity/diffusion coefficient) values in the range of 103-106 cm-1.

  19. Recharging of the ohmic-heating transformer by means of lower-hybrid current drive in the ASDEX tokamak

    NASA Astrophysics Data System (ADS)

    Leuterer, F.; Eckhartt, D.; Söldner, F.; Becker, G.; Bernhardi, K.; Brambilla, M.; Brinkschulte, H.; Derfler, H.; Ditte, U.; Eberhagen, A.; Fussman, G.; Gehre, O.; Gernhardt, J.; Gierke, G. V.; Glock, E.; Gruber, O.; Haas, G.; Hesse, M.; Janeschitz, G.; Karger, F.; Keilhacker, M.; Kissel, S.; Klüber, O.; Kornherr, M.; Lisitano, G.; Magne, R.; Mayer, H. M.; McCormick, K.; Meisel, D.; Mertens, V.; Müller, E. R.; Münich, M.; Murmann, H.; Poschenrieder, W.; Rapp, H.; Ryter, F.; Schmitter, K. H.; Schneider, F.; Siller, G.; Smeulders, P.; Steuer, K. H.; Vien, T.; Wagner, F.; Woyna, F. V.; Zouhar, M.

    1985-07-01

    Recharging of the Ohmic-heating transformer of a tokamak by means of lower-hybrid waves is demonstrated experimentally in ASDEX. The results are analyzed on the basis of a simple transformer circuit. A recharging efficiency is defined and found to depend on rf power, plasma density, and plasma resistivity modified by the applied rf power. Up to now, we achieved in our recharging experiments in ASDEX a flux swing of FİOHMdt=0.24 V sec, at an rf power of PRF=690 kW, with a pulse duration of 1 sec, while maintaining a plasma with n¯e=4×1012 cm-3 and Ip=290 kA.

  20. CEBAF beam loss accounting

    SciTech Connect

    Ursic, R.; Mahoney, K.; Hovater, C.; Hutton, A.; Sinclair, C.

    1995-12-31

    This paper describes the design and implementation of a beam loss accounting system for the CEBAF electron accelerator. This system samples the beam curent throughout the beam path and measures the beam current accurately. Personnel Safety and Machine Protection systems use this system to turn off the beam when hazardous beam losses occur.