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Sample records for dielectric wall accelerator

  1. Enhanced dielectric-wall linear accelerator

    Science.gov (United States)

    Sampayan, Stephen E.; Caporaso, George J.; Kirbie, Hugh C.

    1998-01-01

    A dielectric-wall linear accelerator is enhanced by a high-voltage, fast e-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators. A high voltage is placed between the electrodes sufficient to stress the voltage breakdown of the insulator on command. A light trigger, such as a laser, is focused along at least one line along the edge surface of the laminated alternating layers of isolated conductors and insulators extending between the electrodes. The laser is energized to initiate a surface breakdown by a fluence of photons, thus causing the electrical switch to close very promptly. Such insulators and lasers are incorporated in a dielectric wall linear accelerator with Blumlein modules, and phasing is controlled by adjusting the length of fiber optic cables that carry the laser light to the insulator surface.

  2. Virtual gap dielectric wall accelerator

    Science.gov (United States)

    Caporaso, George James; Chen, Yu-Jiuan; Nelson, Scott; Sullivan, Jim; Hawkins, Steven A

    2013-11-05

    A virtual, moving accelerating gap is formed along an insulating tube in a dielectric wall accelerator (DWA) by locally controlling the conductivity of the tube. Localized voltage concentration is thus achieved by sequential activation of a variable resistive tube or stalk down the axis of an inductive voltage adder, producing a "virtual" traveling wave along the tube. The tube conductivity can be controlled at a desired location, which can be moved at a desired rate, by light illumination, or by photoconductive switches, or by other means. As a result, an impressed voltage along the tube appears predominantly over a local region, the virtual gap. By making the length of the tube large in comparison to the virtual gap length, the effective gain of the accelerator can be made very large.

  3. ELECTROMAGNETIC SIMULATIONS OF LINEAR PROTON ACCELERATOR STRUCTURES USING DIELECTRIC WALL ACCELERATORS

    International Nuclear Information System (INIS)

    Nelson, S; Poole, B; Caporaso, G

    2007-01-01

    Proton accelerator structures for medical applications using Dielectric Wall Accelerator (DWA) technology allow for the utilization of high electric field gradients on the order of 100 MV/m to accelerate the proton bunch. Medical applications involving cancer therapy treatment usually desire short bunch lengths on the order of hundreds of picoseconds in order to limit the extent of the energy deposited in the tumor site (in 3D space, time, and deposited proton charge). Electromagnetic simulations of the DWA structure, in combination with injections of proton bunches have been performed using 3D finite difference codes in combination with particle pushing codes. Electromagnetic simulations of DWA structures includes these effects and also include the details of the switch configuration and how that switch time affects the electric field pulse which accelerates the particle beam

  4. SU-E-T-512: Electromagnetic Simulations of the Dielectric Wall Accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Uselmann, A; Mackie, T [University of Wisconsin and Morgridge Institute for Research, Madison, WI (United States)

    2014-06-01

    Purpose: To characterize and parametrically study the key components of a dielectric wall accelerator through electromagnetic modeling and particle tracking. Methods: Electromagnetic and particle tracking simulations were performed using a commercial code (CST Microwave Studio, CST Inc.) utilizing the finite integration technique. A dielectric wall accelerator consists of a series of stacked transmission lines sequentially fired in synchrony with an ion pulse. Numerous properties of the stacked transmission lines, including geometric, material, and electronic properties, were analyzed and varied in order to assess their impact on the transverse and axial electric fields. Additionally, stacks of transmission lines were simulated in order to quantify the parasitic effect observed in closely packed lines. Particle tracking simulations using the particle-in-cell method were performed on the various stacks to determine the impact of the above properties on the resultant phase space of the ions. Results: Examination of the simulation results show that novel geometries can shape the accelerating pulse in order to reduce the energy spread and increase the average energy of accelerated ions. Parasitic effects were quantified for various geometries and found to vary with distance from the end of the transmission line and along the beam axis. An optimal arrival time of an ion pulse relative to the triggering of the transmission lines for a given geometry was determined through parametric study. Benchmark simulations of single transmission lines agree well with published experimental results. Conclusion: This work characterized the behavior of the transmission lines used in a dielectric wall accelerator and used this information to improve them in novel ways. Utilizing novel geometries, we were able to improve the accelerating gradient and phase space of the accelerated particle bunch. Through simulation, we were able to discover and optimize design issues with the device at

  5. Engineering Prototype for a Compact Medical Dielectric Wall Accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Zografos, Anthony; Hening, Andy; Joshkin, Vladimir; Leung, Kevin; Pearson, Dave; Pearce-Percy, Henry; Rougieri, Mario; Parker, Yoko; Weir, John [CPAC, Livermore, CA (United States); Blackfield, Donald; Chen, Yu-Jiuan; Falabella, Steven; Guethlein, Gary; Poole, Brian [Lawrence Livermore National Laboratory, Livermore, CA (United States); Hamm, Robert W. [R and M Technical Enterprises, Pleasanton, CA (United States); Becker, Reinard [Scientific Software Service, Gelnhausen (Germany)

    2011-12-13

    A compact accelerator system architecture based on the dielectric wall accelerator (DWA) for medical proton beam therapy has been developed by the Compact Particle Acceleration Corporation (CPAC). The major subsystems are a Radio Frequency Quadrupole (RFQ) injector linac, a pulsed kicker to select the desired proton bunches, and a DWA linear accelerator incorporating a high gradient insulator (HGI) with stacked Blumleins to produce the required acceleration energy. The Blumleins are switched with solid state laser-driven optical switches integrated into the Blumlein assemblies. Other subsystems include a high power pulsed laser, fiber optic distribution system, electrical charging system, and beam diagnostics. An engineering prototype has been constructed and characterized, and these results will be used within the next three years to develop an extremely compact 150 MeV system capable of modulating energy, beam current, and spot size on a shot-to-shot basis. This paper presents the details the engineering prototype, experimental results, and commercialization plans.

  6. Engineering Prototype for a Compact Medical Dielectric Wall Accelerator

    International Nuclear Information System (INIS)

    Zografos, Anthony; Hening, Andy; Joshkin, Vladimir; Leung, Kevin; Pearson, Dave; Pearce-Percy, Henry; Rougieri, Mario; Parker, Yoko; Weir, John; Blackfield, Donald; Chen, Yu-Jiuan; Falabella, Steven; Guethlein, Gary; Poole, Brian; Hamm, Robert W.; Becker, Reinard

    2011-01-01

    A compact accelerator system architecture based on the dielectric wall accelerator (DWA) for medical proton beam therapy has been developed by the Compact Particle Acceleration Corporation (CPAC). The major subsystems are a Radio Frequency Quadrupole (RFQ) injector linac, a pulsed kicker to select the desired proton bunches, and a DWA linear accelerator incorporating a high gradient insulator (HGI) with stacked Blumleins to produce the required acceleration energy. The Blumleins are switched with solid state laser-driven optical switches integrated into the Blumlein assemblies. Other subsystems include a high power pulsed laser, fiber optic distribution system, electrical charging system, and beam diagnostics. An engineering prototype has been constructed and characterized, and these results will be used within the next three years to develop an extremely compact 150 MeV system capable of modulating energy, beam current, and spot size on a shot-to-shot basis. This paper presents the details the engineering prototype, experimental results, and commercialization plans.

  7. Nanosecond pulse-width electron diode based on dielectric wall accelerator technology

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Quantang, E-mail: zhaoquantang@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Z.M.; Yuan, P.; Cao, S.C.; Shen, X.K.; Jing, Y. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Yu, C.S. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Li, Z.P.; Liu, M.; Xiao, R.Q. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zong, Y.; Wang, Y.R. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhao, H.W. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

    2013-11-21

    An electron diode using a short section of dielectric wall accelerator (DWA) has been under development at the Institute of Modern Physics (IMP), Chinese Academy of Sciences. Tests have been carried out with spark gap switches triggered by lasers. The stack voltage efficiency of a four-layer of Blumleins reached about 60–70% with gas filled spark gap switching. The generated pulse voltage of peak amplitude of 23 kV and pulse width of 5 ns is used to extract and accelerate an electron beam of 320 mA, measured by a fast current transformer. A nanosecond pulse width electron diode was achieved successfully. Furthermore, the principle of a DWA is well proven and the development details and discussions are presented in this article. -- Highlights: •The key technology of DWA, including switches and pulse forming lines were studied. •The SiC PCSS obtained from Shanghai Institute were tested. •Two layers ZIP lines (new structure) and four layers Blumlein lines were studied with laser triggered spark gap switches. •A nanosecond pulse-width electron diode based on DWA technologies is achieved and studied experimentally. •The principle of DWA is also proved by the diode.

  8. A preliminary design of the collinear dielectric wakefield accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Zholents, A.; Gai, W.; Doran, S.; Lindberg, R.; Power, J.G.; Strelnikov, N.; Sun, Y.; Trakhtenberg, E.; Vasserman, I. [ANL, Argonne, IL 60439 (United States); Jing, C.; Kanareykin, A.; Li, Y. [Euclid Techlabs LLC, Solon, OH 44139 (United States); Gao, Q. [Tsinghua University, Beijing (China); Shchegolkov, D.Y.; Simakov, E.I. [LANL, Los Alamos, NM 87545 (United States)

    2016-09-01

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

  9. Cast dielectric composite linear accelerator

    Science.gov (United States)

    Sanders, David M [Livermore, CA; Sampayan, Stephen [Manteca, CA; Slenes, Kirk [Albuquerque, NM; Stoller, H M [Albuquerque, NM

    2009-11-10

    A linear accelerator having cast dielectric composite layers integrally formed with conductor electrodes in a solventless fabrication process, with the cast dielectric composite preferably having a nanoparticle filler in an organic polymer such as a thermosetting resin. By incorporating this cast dielectric composite the dielectric constant of critical insulating layers of the transmission lines of the accelerator are increased while simultaneously maintaining high dielectric strengths for the accelerator.

  10. 3D Simulations for a Micron-Scale, Dielectric-Based Acceleration Experiment

    International Nuclear Information System (INIS)

    Yoder, R. B.; Travish, G.; Xu Jin; Rosenzweig, J. B.

    2009-01-01

    An experimental program to demonstrate a dielectric, slab-symmetric accelerator structure has been underway for the past two years. These resonant devices are driven by a side-coupled 800-nm laser and can be configured to maintain the field profile necessary for synchronous acceleration and focusing of relativistic or nonrelativistic particles. We present 3D simulations of various versions of the structure geometry, including a metal-walled structure relevant to ongoing cold tests on resonant properties, and an all-dielectric structure to be constructed for a proof-of-principle acceleration experiment.

  11. Dielectric-Lined High-Gradient Accelerator Structure

    Energy Technology Data Exchange (ETDEWEB)

    Jay L. Hirshfield

    2012-04-24

    operating at 30 GHz. It was shown that the ratio of maximum surface electric field to accelerating field at the metal wall is only 0.35-0.4 for DLA, much smaller than the value 2.2 for HDS; and the ratio of surface magnetic field to accelerating field is 3.0 mA/V for DLA, compared with 3.45 mA/V for HDS. These values bode well for DLA in helping to avoid breakdown and to reducing pulsed surface heating and fatigue. The shunt impedance is found to be 160-175 M{Omega}/m for DLA, as compared to 99 M{Omega}/m for HDS. Conclusions are reached from this project that CVD diamond appears promising as a dielectric with a high threshold for RF breakdown, and that rectangular accelerator structures can be devised using planar CVD diamond elements that could be operated at higher acceleration gradients with low probability of RF breakdown, as compared with corresponding all-metallic structures.

  12. Dielectric-Lined High-Gradient Accelerator Structure

    International Nuclear Information System (INIS)

    Hirshfield, Jay L.

    2012-01-01

    GHz. It was shown that the ratio of maximum surface electric field to accelerating field at the metal wall is only 0.35-0.4 for DLA, much smaller than the value 2.2 for HDS; and the ratio of surface magnetic field to accelerating field is 3.0 mA/V for DLA, compared with 3.45 mA/V for HDS. These values bode well for DLA in helping to avoid breakdown and to reducing pulsed surface heating and fatigue. The shunt impedance is found to be 160-175 M(Omega)/m for DLA, as compared to 99 M(Omega)/m for HDS. Conclusions are reached from this project that CVD diamond appears promising as a dielectric with a high threshold for RF breakdown, and that rectangular accelerator structures can be devised using planar CVD diamond elements that could be operated at higher acceleration gradients with low probability of RF breakdown, as compared with corresponding all-metallic structures.

  13. Injector and beam transport simulation study of proton dielectric wall accelerator

    International Nuclear Information System (INIS)

    Zhao, Quantang; Yuan, P.; Zhang, Z.M.; Cao, S.C; Shen, X.K.; Jing, Y.; Ma, Y.Y.; Yu, C.S.; Li, Z.P.; Liu, M.; Xiao, R.Q.; Zhao, H.W.

    2012-01-01

    A simulation study of a short-pulsed proton injector for, and beam transport in, a dielectric wall accelerator (DWA) has been carried out using the particle-in-cell (PIC) code Warp. It was shown that applying “tilt pulse” voltage waveforms on three electrodes enables the production of a shorter bunch by the injector. The fields in the DWA beam tube were simulated using Computer Simulation Technology’s Microwave Studio (CST MWS) package, with various choices for the boundary conditions. For acceleration in the DWA, the beam transport was simulated with Warp, using applied fields obtained by running CST MWS. Our simulations showed that the electric field at the entrance to the DWA represents a challenging issue for the beam transport. We thus simulated a configuration with a mesh at the entrance of the DWA, intended to improve the entrance field. In these latter simulations, a proton bunch was successfully accelerated from 130 keV to about 36 MeV in a DWA with a length of 36.75 cm. As the beam bunch progresses, its transverse dimensions diminish from (roughly) 0.5×0.5 cm to 0.2×0.4 cm. The beam pulse lengthens from 1 cm to 2 cm due to lack of longitudinal compression fields. -- Highlights: ► A pulse proton injector with tilt voltages on the three electrodes was simulated. ► The fields in different part of the DWA were simulated with CST and analyzed. ► The proton beam transport in DWA was simulated with Warp successfully. ► The simulation can help for designing a real DWA.

  14. Dielectric-wall linear accelerator with a high voltage fast rise time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators

    Science.gov (United States)

    Caporaso, George J.; Sampayan, Stephen E.; Kirbie, Hugh C.

    1998-01-01

    A dielectric-wall linear accelerator is improved by a high-voltage, fast rise-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators. A high voltage is placed between the electrodes sufficient to stress the voltage breakdown of the insulator on command. A light trigger, such as a laser, is focused along at least one line along the edge surface of the laminated alternating layers of isolated conductors and insulators extending between the electrodes. The laser is energized to initiate a surface breakdown by a fluence of photons, thus causing the electrical switch to close very promptly. Such insulators and lasers are incorporated in a dielectric wall linear accelerator with Blumlein modules, and phasing is controlled by adjusting the length of fiber optic cables that carry the laser light to the insulator surface.

  15. Development of a dual-layered dielectric-loaded accelerating structure

    International Nuclear Information System (INIS)

    Jing Chunguang; Kanareykin, Alexei; Kazakov, Sergey; Liu Wanming; Nenasheva, Elizaveta; Schoessow, Paul; Gai Wei

    2008-01-01

    rf Power attenuation is a critical problem in the development of dielectric-loaded structures for particle acceleration. In a previous paper [C. Jing, W. Liu, W. Gai, J. Power, T. Wong, Nucl. Instr. Meth. A 539 (2005) 445] we suggested the use of a Multilayer Dielectric-Loaded Accelerating Structure (MDLA) as a possible approach for reducing the rf losses in a single layer device. The MDLA is based on the principle of Bragg reflection familiar from optics that is used to partially confine the fields inside the dielectric layers and reduce the wall current losses at the outer boundary. We report here on the design, construction and testing of a prototype X-band double-layer structure (2DLA). The measurements show an rf power attenuation for the 2DLA more than ten times smaller than that of a comparable single-layer structure, in good agreement with the analytic results. Testing and operation of MDLAs also requires efficient power coupling from test equipment or rf power systems to the device. We describe the design and construction of two novel structures: a TM 03 mode launcher for cold testing and a power coupler for planned high-gradient experiments

  16. Theory of the dielectric wakefield accelerator

    International Nuclear Information System (INIS)

    Mtingwa, S.K.

    1990-10-01

    The general theory for all angular modes m of the dielectric wakefield accelerator is reformulated. The expressions for the accelerating electric fields and transverse wake forces are written in terms of matrices, the zeros of one of which determine the excitation frequencies of the dielectric structure. In this scheme it is possible to obtain a maximum accelerating gradient of 2.0 megavolts per meter per nanoCoulomb of driver beam charge, for a driver beam of 0.7 millimeters rms bunch length. 29 refs., 5 figs

  17. Coaxial two-channel high-gradient dielectric wakefield accelerator

    Directory of Open Access Journals (Sweden)

    G. V. Sotnikov

    2009-06-01

    Full Text Available A new scheme for a dielectric wakefield accelerator is proposed that employs a cylindrical multizone dielectric structure configured as two concentric dielectric tubes with outer and inner vacuum channels for drive and accelerated bunches. Analytical and numerical studies have been carried out for such coaxial dielectric-loaded structures (CDS for high-gradient acceleration. An analytical theory of wakefield excitation by particle bunches in a multizone CDS has been formulated. Numerical calculations are presented for an example of a CDS using dielectric tubes with dielectric permittivity 5.7, having external diameters of 2.121 and 0.179 mm with inner diameters of 2.095 and 0.1 mm. An annular 5 GeV, 6 nC electron bunch with rms length of 0.035 mm energizes a wakefield on the structure axis having an accelerating gradient of ∼600  MeV/m with a transformer ratio ∼8∶1. The period of the accelerating field is ∼0.33  mm. If the width of the drive bunch channel is decreased, it is possible to obtain an accelerating gradient of >1  GeV/m while keeping the transformer ratio approximately the same. Full numerical simulations using a particle-in-cell code have confirmed results of the linear theory and furthermore have shown the important influence of the quenching wave that restricts the region of the wakefield to within several periods following the drive bunch. Numerical simulations for another example have shown nearly stable transport of drive and accelerated bunches through the CDS, using a short train of drive bunches.

  18. Experimental demonstration of dielectric structure based two beam acceleration

    International Nuclear Information System (INIS)

    Gai, W.; Conde, M. E.; Konecny, R.; Power, J. G.; Schoessow, P.; Sun, X.; Zou, P.

    2000-01-01

    We report on the experimental results of the dielectric based two beam accelerator (step-up transformer). By using a single high charge beam, we have generated and extracted a high power RF pulse from a 7.8 GHz primary dielectric structure and then subsequently transferred to a second accelerating structure with higher dielectric constant and smaller transverse dimensions. We have measured the energy change of a second (witness) beam passing through the acceleration stage. The measured gradient is >4 times the deceleration gradient. The detailed experiment of set-up and results of the measurements are dimmed. Future plans for the development of a 100 MeV demonstration accelerator based on this technique is presented

  19. Experimental demonstration of dielectric structure based two beam acceleration.

    Energy Technology Data Exchange (ETDEWEB)

    Gai, W.; Conde, M. E.; Konecny, R.; Power, J. G.; Schoessow, P.; Sun, X.; Zou, P.

    2000-11-28

    We report on the experimental results of the dielectric based two beam accelerator (step-up transformer). By using a single high charge beam, we have generated and extracted a high power RF pulse from a 7.8 GHz primary dielectric structure and then subsequently transferred to a second accelerating structure with higher dielectric constant and smaller transverse dimensions. We have measured the energy change of a second (witness) beam passing through the acceleration stage. The measured gradient is >4 times the deceleration gradient. The detailed experiment of set-up and results of the measurements are dimmed. Future plans for the development of a 100 MeV demonstration accelerator based on this technique is presented.

  20. Coherent multimoded dielectric wakefield accelerators

    International Nuclear Information System (INIS)

    Power, J.

    1998-01-01

    There has recently been a study of the potential uses of multimode dielectric structures for wakefield acceleration [1]. This technique is based on adjusting the wakefield modes of the structure to constructively interfere at certain delays with respect to the drive bunch, thus providing an accelerating gradient enhancement over single mode devices. In this report we examine and attempt to clarify the issues raised by this work in the light of the present state of the art in wakefield acceleration

  1. Development of High-Gradient Dielectric Laser-Driven Particle Accelerator Structures

    Energy Technology Data Exchange (ETDEWEB)

    Byer, Robert L. [Stanford Univ., CA (United States). Edward L. Ginzton Lab.

    2013-11-07

    The thrust of Stanford's program is to conduct research on high-gradient dielectric accelerator structures driven with high repetition-rate, tabletop infrared lasers. The close collaboration between Stanford and SLAC (Stanford Linear Accelerator Center) is critical to the success of this project, because it provides a unique environment where prototype dielectric accelerator structures can be rapidly fabricated and tested with a relativistic electron beam.

  2. COAXIAL TWO-CHANNEL DIELECTRIC WAKE FIELD ACCELERATOR

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L. [Omega-P, Inc.

    2013-04-30

    Theory, computations, and experimental apparatus are presented that describe and are intended to confirm novel properties of a coaxial two-channel dielectric wake field accelerator. In this configuration, an annular drive beam in the outer coaxial channel excites multimode wakefields which, in the inner channel, can accelerate a test beam to an energy much higher than the energy of the drive beam. This high transformer ratio is the result of judicious choice of the dielectric structure parameters, and of the phase separation between drive bunches and test bunches. A structure with cm-scale wakefields has been build for tests at the Argonne Wakefield Accelerator Laboratory, and a structure with mm-scale wakefields has been built for tests at the SLAC FACET facility. Both tests await scheduling by the respective facilities.

  3. On-Chip Laser-Power Delivery System for Dielectric Laser Accelerators

    Science.gov (United States)

    Hughes, Tyler W.; Tan, Si; Zhao, Zhexin; Sapra, Neil V.; Leedle, Kenneth J.; Deng, Huiyang; Miao, Yu; Black, Dylan S.; Solgaard, Olav; Harris, James S.; Vuckovic, Jelena; Byer, Robert L.; Fan, Shanhui; England, R. Joel; Lee, Yun Jo; Qi, Minghao

    2018-05-01

    We propose an on-chip optical-power delivery system for dielectric laser accelerators based on a fractal "tree-network" dielectric waveguide geometry. This system replaces experimentally demanding free-space manipulations of the driving laser beam with chip-integrated techniques based on precise nanofabrication, enabling access to orders-of-magnitude increases in the interaction length and total energy gain for these miniature accelerators. Based on computational modeling, in the relativistic regime, our laser delivery system is estimated to provide 21 keV of energy gain over an acceleration length of 192 μ m with a single laser input, corresponding to a 108-MV/m acceleration gradient. The system may achieve 1 MeV of energy gain over a distance of less than 1 cm by sequentially illuminating 49 identical structures. These findings are verified by detailed numerical simulation and modeling of the subcomponents, and we provide a discussion of the main constraints, challenges, and relevant parameters with regard to on-chip laser coupling for dielectric laser accelerators.

  4. Dielectric laser acceleration of non-relativistic electrons at a photonic structure

    Energy Technology Data Exchange (ETDEWEB)

    Breuer, John

    2013-08-29

    This thesis reports on the observation of dielectric laser acceleration of non-relativistic electrons via the inverse Smith-Purcell effect in the optical regime. Evanescent modes in the vicinity of a periodic grating structure can travel at the same velocity as the electrons along the grating surface. A longitudinal electric field component is used to continuously impart momentum onto the electrons. This is only possible in the near-field of a suitable photonic structure, which means that the electron beam has to pass the structure within about one wavelength. In our experiment we exploit the third spatial harmonic of a single fused silica grating excited by laser pulses derived from a Titanium:sapphire oscillator and accelerate non-relativistic 28 keV electrons. We measure a maximum energy gain of 280 eV, corresponding to an acceleration gradient of 25 MeV/m, already comparable with state-of-the-art radio-frequency linear accelerators. To experience this acceleration gradient the electrons approach the grating closer than 100 nm. We present the theory behind grating-based particle acceleration and discuss simulation results of dielectric laser acceleration in the near-field of photonic grating structures, which is excited by near-infrared laser light. Our measurements show excellent agreement with our simulation results and therefore confirm the direct acceleration with the light field. We further discuss the acceleration inside double grating structures, dephasing effects of non-relativistic electrons as well as the space charge effect, which can limit the attainable peak currents of these novel accelerator structures. The photonic structures described in this work can be readily concatenated and therefore represent a scalable realization of dielectric laser acceleration. Furthermore, our structures are directly compatible with the microstructures used for the acceleration of relativistic electrons demonstrated in parallel to this work by our collaborators in

  5. Numerical simulations of intense charged particle beam propagation in a dielectric wakefield accelerator

    International Nuclear Information System (INIS)

    Gai, W.; Kanareykin, A.D.; Kustov, A.L.; Simpson, J.

    1995-01-01

    The propagation of an intense electron beam through a long dielectric tube is a critical issue for the success of the dielectric wakefield acceleration scheme. Due to the head-tail instability, a high current charged particle beam cannot propagate long distance without external focusing. In this paper we examine the beam handling and control problem in the dielectric wakefield accelerator. We show that for the designed 15.6 GHz and 20 GHz dielectric structures a 150 MeV, 40 endash 100 nC beam can be controlled and propagate up to 5 meters without significant particle losses by using external applied focusing and defocusing channel (FODO) around the dielectric tube. Particle dynamics of the accelerated beam is also studied. Our results show that for typical dielectric acceleration structures, the head-tail instabilities can be conveniently controlled in the same way as the driver beam. copyright 1995 American Institute of Physics

  6. DIELECTRIC WAKE FIELD RESONATOR ACCELERATOR MODULE

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L.

    2013-11-06

    Results are presented from experiments, and numerical analysis of wake fields set up by electron bunches passing through a cylindrical or rectangular dielectric-lined structure. These bunches excite many TM-modes, with Ez components of the wake fields sharply localized on the axis of the structure periodically behind the bunches. The experiment with the cylindrical structure, carried out at ATF Brookhaven National Laboratory, used up to three 50 MeV bunches spaced by one wake field period (21 cm) to study the superposition of wake fields by measuring the energy loss of each bunch after it passed through the 53-cm long dielectric element. The millimeter-wave spectrum of radiation excited by the passage of bunches is also studied. Numerical analysis was aimed not only to simulate the behavior of our device, but in general to predict dielectric wake field accelerator performance. It is shown that one needs to match the radius of the cylindrical dielectric channel with the bunch longitudinal rms-length to achieve optimal performance.

  7. Two-Channel Dielectric Wake Field Accelerator

    International Nuclear Information System (INIS)

    Hirshfield, Jay L.

    2012-01-01

    Experimental results are reported for test beam acceleration and deflection in a two-channel, cm-scale, rectangular dielectric-lined wakefield accelerator structure energized by a 14-MeV drive beam. The dominant waveguide mode of the structure is at ∼30 GHz, and the structure is configured to exhibit a high transformer ratio (∼12:1). Accelerated bunches in the narrow secondary channel of the structure are continuously energized via Cherenkov radiation that is emitted by a drive bunch moving in the wider primary channel. Observed energy gains and losses, transverse deflections, and changes in the test bunch charge distribution compare favorably with predictions of theory.

  8. Development of a 20 MeV Dielectric-Loaded Test Accelerator

    International Nuclear Information System (INIS)

    Gold, Steven H.; Fliflet, Arne W.; Lombardi, Marcie; Kinkead, Allen K.; Gai, Wei; Power, John G.; Konecny, Richard; Long, Jidong; Jing, Chunguang; Tantawi, Sami G.; Nantista, Christopher D.; Bruce, Ralph W.; Lewis, David III

    2006-01-01

    This paper presents a progress report on a joint project by the Naval Research Laboratory (NRL) and Argonne National Laboratory (ANL), in collaboration with the Stanford Linear Accelerator Center (SLAC), to develop a dielectric-loaded test accelerator in the magnicon facility at NRL. The accelerator will be powered by an experimental 11.424-GHz magnicon amplifier that presently produces 25 MW of output power in a ∼250-ns pulse at up to 10 Hz. The accelerator will include a 5-MeV electron injector originally developed at the Tsinghua University in Beijing, China, and can incorporate DLA structures up to 0.5 m in length. The DLA structures are being developed by ANL, and shorter test structures fabricated from a variety of dielectric materials have undergone testing at NRL at gradients up to ∼8 MV/m. SLAC has developed components to distribute the power from the two magnicon output arms to the injector and to the DLA accelerating structure with separate control of the power ratio and relative phase. RWBruce Associates, Inc., working with NRL, has investigated means to join short ceramic sections into a continuous accelerator tube by a brazing process using an intense 83-GHz beam. The installation and testing of the first dielectric-loaded test accelerator, including injector, DLA test structure, and spectrometer, should take place within the next year

  9. Optical design for increased interaction length in a high gradient dielectric laser accelerator

    OpenAIRE

    Cesar, D.; Maxson, J.; Musumeci, P.; Shen, X.; England, R. J.; Wootton, K. P.

    2018-01-01

    We present a methodology for designing and measuring pulse front tilt in an ultrafast laser for use in dielectric laser acceleration. Previous research into dielectric laser accelerating modules has focused on measuring high accelerating gradients in novel structures, but has done so only for short electron-laser coupling lengths. Here we demonstrate an optical design to extend the laser-electron interaction to 1mm.

  10. Beam manipulation and acceleration with Dielectric-Lined Waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Lemery, Francois [Northern Illinois Univ., DeKalb, IL (United States)

    2015-06-01

    The development of next-generation TeV+ electron accelerators will require either immense footprints based on conventional acceleraton techniques or the development of new higher{gradient acceleration methods. One possible alternative is beam-driven acceleration in a high-impedance medium such as a dielectric-lined-waveguide (DLW), where a highcharge bunch passes through a DLW and can excite gradients on the order of GV/m. An important characteristic of this acceleration class is the transformer ratio which characterizes the energy transfer of the scheme. This dissertation discusses alternative methods to improve the transformer ratio for beam-driven acceleration and also considers the use of DLWs for beam manipulation at low energy.

  11. Development of a 20 MeV Dielectric-Loaded Accelerator Test Facility

    International Nuclear Information System (INIS)

    Gold, Steven H.; Fliflet, Arne W.; Kinkead, Allen K.; Gai Wei; Power, John G.; Konecny, Richard; Jing Chunguang; Tantawi, Sami G.; Nantista, Christopher D.; Hu, Y.; Chen, H.; Tang, C.; Lin, Y.; Bruce, Ralph W.; Bruce, Robert L.; Lewis, David III

    2004-01-01

    This paper describes a joint project by the Naval Research Laboratory (NRL) and Argonne National Laboratory (ANL), in collaboration with the StanFord Linear Accelerator Center (SLAC), to develop a dielectric-loaded accelerator (DLA) test facility powered by a high-power 11.424-GHz magnicon amplifier. The magnicon can presently produce 25 MW of output power in a 250-ns pulse at 10 Hz, and efforts are in progress to increase this to 50 MW. The facility will include a 5 MeV electron injector being developed by the Accelerator Laboratory of Tsinghua University in Beijing, China. The DLA test structures are being developed by ANL, and some have undergone testing at NRL at gradients up to ∼8 MV/m. SLAC is developing a means to combine the two magnicon output arms, and to drive an injector and accelerator with separate control of the power ratio and relative phase. RWBruce Associates, Inc., working with NRL, is developing a means to join short ceramic sections into a continuous accelerator tube by ceramic brazing using an intense millimeter-wave beam. The installation and testing of the first dielectric-loaded test accelerator, including injector, DLA structure, and spectrometer, should take place within the next year. The facility will be used for testing DLA structures using a variety of materials and configurations, and also for testing other X-band accelerator concepts. The initial goal is to produce a compact 20 MeV dielectric-loaded test accelerator

  12. Dielectric Wakefield Accelerator to drive the future FEL Light Source.

    Energy Technology Data Exchange (ETDEWEB)

    Jing, C.; Power, J.; Zholents, A. (Accelerator Systems Division (APS)); ( HEP); (LLC)

    2011-04-20

    X-ray free-electron lasers (FELs) are expensive instruments and a large part of the cost of the entire facility is driven by the accelerator. Using a high-energy gain dielectric wake-field accelerator (DWA) instead of the conventional accelerator may provide a significant cost saving and reduction of the facility size. In this article, we investigate using a collinear dielectric wakefield accelerator to provide a high repetition rate, high current, high energy beam to drive a future FEL x-ray light source. As an initial case study, a {approx}100 MV/m loaded gradient, 850 GHz quartz dielectric based 2-stage, wakefield accelerator is proposed to generate a main electron beam of 8 GeV, 50 pC/bunch, {approx}1.2 kA of peak current, 10 x 10 kHz (10 beamlines) in just 100 meters with the fill factor and beam loading considered. This scheme provides 10 parallel main beams with one 100 kHz drive beam. A drive-to-main beam efficiency {approx}38.5% can be achieved with an advanced transformer ratio enhancement technique. rf power dissipation in the structure is only 5 W/cm{sup 2} in the high repetition rate, high gradient operation mode, which is in the range of advanced water cooling capability. Details of study presented in the article include the overall layout, the transform ratio enhancement scheme used to increase the drive to main beam efficiency, main wakefield linac design, cooling of the structure, etc.

  13. High current electron beam acceleration in dielectric-filled RF cavities

    International Nuclear Information System (INIS)

    Faehl, R.J.; Keinigs, R.K.

    1996-01-01

    The acceleration of charged particles in radio frequency (RF) cavities is a widely used mode in high energy accelerators. Advantages include very high accelerating gradients and very stable phase control. A traditional limitation for such acceleration has been their use for intense, high current beam generation. This constraint arises from the inability to store a large amount of electromagnetic energy in the cavity and from loading effects of the beam on the cavity. The authors have studied a simple modification to transcend these limitations. Following Humphries and Huang, they have conducted analytic and numerical investigations of RF accelerator cavities in which a high dielectric constant material, such as water, replaces most of the cavity volume. This raises the stored energy in a cavity of given dimensions by a factor var-epsilon/var-epsilon 0 . For a water fill, var-epsilon/var-epsilon 0 ∼ 80, depending on the frequency. This introduction of high dielectric constant material into the cavity reduces the resonant frequencies by a factor of (var-epsilon/var-epsilon 0 ) 1/2 . This reduced operating frequency mans that existing high efficiency power supplies, at lower frequencies, can be used for an accelerator

  14. Multipactor Physics, Acceleration, and Breakdown in Dielectric-Loaded Accelerating Structures

    International Nuclear Information System (INIS)

    Fischer, Richard P.; Gold, Steven H.

    2016-01-01

    The objective of this 3-year program is to study the physics issues associated with rf acceleration in dielectric-loaded accelerating (DLA) structures, with a focus on the key issue of multipactor loading, which has been found to cause very significant rf power loss in DLA structures whenever the rf pulsewidth exceeds the multipactor risetime (~10 ns). The experiments are carried out in the X-band magnicon laboratory at the Naval Research Laboratory (NRL) in collaboration with Argonne National Laboratory (ANL) and Euclid Techlabs LLC, who develop the test structures with support from the DoE SBIR program. There are two main elements in the research program: (1) high-power tests of DLA structures using the magnicon output (20 MW @11.4 GHz), and (2) tests of electron acceleration in DLA structures using relativistic electrons from a compact X-band accelerator. The work during this period has focused on a study of the use of an axial magnetic field to suppress multipactor in DLA structures, with several new high power tests carried out at NRL, and on preparation of the accelerator for the electron acceleration experiments.

  15. Operation regimes of a dielectric laser accelerator

    Science.gov (United States)

    Hanuka, Adi; Schächter, Levi

    2018-04-01

    We investigate three operation regimes in dielectric laser driven accelerators: maximum efficiency, maximum charge, and maximum loaded gradient. We demonstrate, using a self-consistent approach, that loaded gradients of the order of 1 to 6 [GV/m], efficiencies of 20% to 80%, and electrons flux of 1014 [el/s] are feasible, without significant concerns regarding damage threshold fluence. The latter imposes that the total charge per squared wavelength is constant (a total of 106 per μm2). We conceive this configuration as a zero-order design that should be considered for the road map of future accelerators.

  16. Observation of 690 MV m-1 Electron Accelerating Gradient with a Laser-Driven Dielectric Microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Wootton, K.P.; Wu, Z.; /SLAC; Cowan, B.M.; /Tech-X, Boulder; Hanuka, A.; /SLAC /Technion; Makasyuk, I.V.; /SLAC; Peralta, E.A.; Soong, K.; Byer, R.L.; /Stanford U.; England, R.J.; /SLAC

    2016-06-27

    Acceleration of electrons using laser-driven dielectric microstructures is a promising technology for the miniaturization of particle accelerators. In this work, experimental results are presented of relativistic electron acceleration with 690±100 MVm-1 gradient. This is a record-high accelerating gradient for a dielectric microstructure accelerator, nearly doubling the previous record gradient. To reach higher acceleration gradients the present experiment employs 90 fs duration laser pulses.

  17. Experimental Investigation of an X-Band Tunable Dielectric Accelerating Structure

    CERN Document Server

    Kanareykin, Alex; Karmanenko, Sergei F; Nenasheva, Elisaveta; Power, John G; Schoessow, Paul; Semenov, Alexei

    2005-01-01

    Experimental study of a new scheme to tune the resonant frequency for dielectric based accelerating structure (driven either by the wakefield of a beam or an external rf source) is underway. The structure consists of a single layer of conventional dielectric surrounded by a very thin layer of ferroelectric material situated on the outside. Carefully designed electrodes are attached to a thin layer of ferroelectric material. A DC bias can be applied to the electrodes to change the permittivity of the ferroelectric layer and therefore, the dielectric overall resonant frequency can be tuned. In this paper, we present the test results for an 11.424 GHz rectangular DLA prototype structure that the ferroelectric material's dielectric constant of 500 and show that a frequency tuning range of 2% can be achieved. If successful, this scheme would compensate for structure errors caused by ceramic waveguide machining tolerances and dielectric constant heterogeneity.

  18. Dielectric properties of single wall carbon nanotubes-based gelatin phantoms

    Science.gov (United States)

    Altarawneh, M. M.; Alharazneh, G. A.; Al-Madanat, O. Y.

    In this work, we report the dielectric properties of Single wall Carbon Nanotubes (SWCNTs)-based phantom that is mainly composed of gelatin and water. The fabricated gelatin-based phantom with desired dielectric properties was fabricated and doped with different concentrations of SWCNTs (e.g., 0%, 0.05%, 0.10%, 0.15%, 0.2%, 0.4% and 0.6%). The dielectric constants (real ɛ‧ and imaginary ɛ‧‧) were measured at different positions for each sample as a function of frequency (0.5-20GHz) and concentrations of SWCNTs and their averages were found. The Cole-Cole plot (ɛ‧ versus ɛ‧‧) was obtained for each concentration of SWCNTs and was used to obtain the static dielectric constant ɛs, the dielectric constant at the high limit of frequency ɛ∞ and the average relaxation time τ. The measurements showed that the fabricated samples are in good homogeneity and the SWCNTs are dispersed well in the samples as an acceptable standard deviation is achieved. The study showed a linear increase in the static dielectric constant ɛs and invariance of the average relaxation time τ and the value of ɛ∞ at room temperature for the investigated concentrations of SWCNTs.

  19. Femtosecond planar electron beam source for micron-scale dielectric wake field accelerator

    Directory of Open Access Journals (Sweden)

    T. C. Marshall

    2001-12-01

    Full Text Available A new accelerator, LACARA (laser-driven cyclotron autoresonance accelerator, under construction at the Accelerator Test Facility at Brookhaven National Laboratory, is to be powered by a 1 TW CO_{2} laser beam and a 50 MeV injected electron pulse. LACARA will produce inside a 2 m, 6 T solenoid a 100 MeV gyrating electron bunch, with ∼3% energy spread, approximately 1 psec in length with particles advancing in phase at the laser frequency, executing one cycle each 35 fsec. A beamstop with a small off axis channel will transmit a short beam pulse every optical cycle, thereby producing a train of about 30, 3.5 fsec long, 1–3 pC microbunches for each laser pulse. We describe here a novel accelerator, a micron-scale dielectric wake field accelerator driven by a 500 MeV LACARA-type injector that takes the output train of microbunches and transforms them into a near-rectangular cross section having a narrow dimension of ∼10 μm and height of ∼150 μm using a magnetic quadrupole; these bunches may be injected into a planar dielectric-lined waveguide (slightly larger than the bunch where cumulative buildup of wake fields can lead to an accelerating gradient >1 GV/m. This proposed vacuum-based wake field structure is physically rigid and capable of microfabrication accuracy, factors important in staging a large number of accelerator modules. Furthermore, the accelerating gradients it promises are comparable with those for plasma accelerators. A LACARA unit for preparing suitable bunches at 500 MeV is described. Physics issues are discussed, including bunch spreading and transport, bunch shaping, coherent diffraction radiation from the aperture, dielectric breakdown, and bunch stability in the rectangular wake field structure.

  20. A hybrid dielectric and iris loaded periodic accelerating structure

    International Nuclear Information System (INIS)

    Zou, P.; Xiao, L.; Sun, X.; Gai, W.

    2001-01-01

    One disadvantage of conventional iris-loaded accelerating structures is the high ratio of the peak surface electric field to the peak axial electric field useful for accelerating a beam. Typically this ratio E s /E a ≥ 2. The high surface electric field relative to the accelerating gradient may prove to be a limitation for realizing technologies for very high gradient accelerators. In this paper, we present a scheme that uses a hybrid dielectric and iris loaded periodic structure to reduce E s /E a to near unity, while the shunt impedance per unit length r and the quality factor Q compare favorably with conventional metallic structures. The analysis based on MAFIA simulations of such structures shows that we can lower the peak surface electric field close to the accelerating gradient while maintaining high acceleration efficiency as measured by r/Q. Numerical examples of X-band hybrid accelerating structures are given

  1. HIGH-GRADIENT, HIGH-TRANSFORMER-RATIO, DIELECTRIC WAKE FIELD ACCELERATOR

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L

    2012-04-12

    The Phase I work reported here responds to DoE'ss stated need "...to develop improved accelerator designs that can provide very high gradient (>200 MV/m for electrons...) acceleration of intense bunches of particles." Omega-P's approach to this goal is through use of a ramped train of annular electron bunches to drive a coaxial dielectric wakefield accelerator (CDWA) structure. This approach is a direct extension of the CDWA concept from acceleration in wake fields caused by a single drive bunch, to the more efficient acceleration that we predict can be realized from a tailored (or ramped) train of several drive bunches. This is possible because of a much higher transformer ratio for the latter. The CDWA structure itself has a number of unique features, including: a high accelerating gradient G, potentially with G > 1 GeV/m; continuous energy coupling from drive to test bunches without transfer structures; inherent transverse focusing forces for particles in the accelerated bunch; highly stable motion of high charge annular drive bunches; acceptable alignment tolerances for a multi-section system. What is new in the present approach is that the coaxial dielectric structure is now to be energized by-not one-but by a short train of ramped annular-shaped drive bunches moving in the outer coaxial channel of the structure. We have shown that this allows acceleration of an electron bunch traveling along the axis in the inner channel with a markedly higher transformer ratio T than for a single drive bunch. As described in this report, the structure will be a GHz-scale prototype with cm-scale transverse dimensions that is expected to confirm principles that can be applied to the design of a future THz-scale high gradient (> 500 MV/m) accelerator with mm-scale transverse dimensions. We show here a new means to significantly increase the transformer ratio T of the device, and thereby to significantly improve its suitability as a flexible and effective component in

  2. Simulation Studies of the Dielectric Grating as an Accelerating and Focusing Structure

    International Nuclear Information System (INIS)

    Soong, Ken; Peralta, E.A.; Byer, R.L.; Colby, E.

    2011-01-01

    A grating-based design is a promising candidate for a laser-driven dielectric accelerator. Through simulations, we show the merits of a readily fabricated grating structure as an accelerating component. Additionally, we show that with a small design perturbation, the accelerating component can be converted into a focusing structure. The understanding of these two components is critical in the successful development of any complete accelerator. The concept of accelerating electrons with the tremendous electric fields found in lasers has been proposed for decades. However, until recently the realization of such an accelerator was not technologically feasible. Recent advances in the semiconductor industry, as well as advances in laser technology, have now made laser-driven dielectric accelerators imminent. The grating-based accelerator is one proposed design for a dielectric laser-driven accelerator. This design, which was introduced by Plettner, consists of a pair of opposing transparent binary gratings, illustrated in Fig. 1. The teeth of the gratings serve as a phase mask, ensuring a phase synchronicity between the electromagnetic field and the moving particles. The current grating accelerator design has the drive laser incident perpendicular to the substrate, which poses a laser-structure alignment complication. The next iteration of grating structure fabrication seeks to monolithically create an array of grating structures by etching the grating's vacuum channel into a fused silica wafer. With this method it is possible to have the drive laser confined to the plane of the wafer, thus ensuring alignment of the laser-and-structure, the two grating halves, and subsequent accelerator components. There has been previous work using 2-dimensional finite difference time domain (2D-FDTD) calculations to evaluate the performance of the grating accelerator structure. However, this work approximates the grating as an infinite structure and does not accurately model a

  3. A monolithic relativistic electron beam source based on a dielectric laser accelerator structure

    International Nuclear Information System (INIS)

    McNeur, Josh; Carranza, Nestor; Travish, Gil; Yin Hairong; Yoder, Rodney

    2012-01-01

    Work towards a monolithic device capable of producing relativistic particle beams within a cubic-centimeter is detailed. We will discuss the Micro-Accelerator Platform (MAP), an optical laser powered dielectric accelerator as the main building block of this chip-scale source along with a field enhanced emitter and a region for sub-relativistic acceleration.

  4. Inertial polarization of dielectrics

    OpenAIRE

    Zavodovsky, A. G.

    2011-01-01

    It was proved that accelerated motion of a linear dielectric causes its polarization. Accelerated translational motion of a dielectric's plate leads to the positive charge of the surface facing the direction of motion. Metal plates of a capacitor were used to register polarized charges on a dielectric's surface. Potential difference between the capacitor plates is proportional to acceleration, when acceleration is constant potential difference grows with the increase of a dielectric's area, o...

  5. Optimized operation of dielectric laser accelerators: Single bunch

    Directory of Open Access Journals (Sweden)

    Adi Hanuka

    2018-05-01

    Full Text Available We introduce a general approach to determine the optimal charge, efficiency and gradient for laser driven accelerators in a self-consistent way. We propose a way to enhance the operational gradient of dielectric laser accelerators by leverage of beam-loading effect. While the latter may be detrimental from the perspective of the effective gradient experienced by the particles, it can be beneficial as the effective field experienced by the accelerating structure, is weaker. As a result, the constraint imposed by the damage threshold fluence is accordingly weakened and our self-consistent approach predicts permissible gradients of ∼10  GV/m, one order of magnitude higher than previously reported experimental results—with unbunched pulse of electrons. Our approach leads to maximum efficiency to occur for higher gradients as compared with a scenario in which the beam-loading effect on the material is ignored. In any case, maximum gradient does not occur for the same conditions that maximum efficiency does—a trade-off set of parameters is suggested.

  6. Proposed Physics Experiments for Laser-Driven Electron Linear Acceleration in a Dielectric Loaded Vacuum, Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Byer, Robert L. [Stanford Univ., CA (United States). Dept. of Applied Physics. Edward L. Ginzton Lab.

    2016-07-08

    This final report summarizes the last three years of research on the development of advanced linear electron accelerators that utilize dielectric wave-guide vacuum channels pumped by high energy laser fields to accelerate beams of electrons.

  7. High power testing oa ANL X-band dielectric-loaded accelerating structures

    International Nuclear Information System (INIS)

    Power, J. G.; Gai, W.; Jing, C.; Konecny, R.; Gold, S. H.; Kinkead, A. K.

    2002-01-01

    In the second phase of a program to develop a compact accelerator based on a dielectric-loaded accelerating structure, we have conducted high power tests on a traveling-wave and a standing-wave prototype. Indications are that the traveling-wave structure achieved an accelerating gradient of 3-5 MV/m before the input coupling window failed, while the standing wave structure was poorly matched at high power due to contamination of copper residue on its coupling window. To solve both of these problems, a new method for coupling RF into the structures has been developed. The new couplers and the rest of the modular structure are currently under construction and will be tested at the Naval Research Laboratory shortly

  8. Development of a Laser-Powered Dielectric Structure-Based Accelerator as a Stand-Alone Particle Source

    International Nuclear Information System (INIS)

    Yoder, R. B.; Travish, G.; Arab, E. R.; Fong, D.; Hoyer, Z.; Lacroix, U. H.; Vartanian, N.; Rosenzweig, J. B.

    2010-01-01

    An experimental program to develop and build a dielectric-based slab-symmetric structure (the micro-accelerator platform, or MAP) for generating and accelerating low-energy electrons is underway at UCLA and Manhattanville College. This optical acceleration structure is effectively a resonant cavity powered by a side-coupled laser, and has applications as a radiation source for medicine or industry. We present recent experimental and computational results on the accelerator, and progress toward its incorporation into a self-contained particle source. Such a particle source would incorporate a micron-scale electron emitter and a non-relativistic capture region to enable self-injection into the synchronous field within the accelerator. A prototype of the accelerator itself has been constructed from candidate dielectric materials using micromanufacturing techniques; the current status of the testing program is described. A novel electron emitter incorporating pyroelectric crystals with field-enhancing tips has been demonstrated to produce steady currents; the results are dependent on tip geometry, and appear suitable for injection into a microstructure. Extension of the MAP concept to non-relativistic velocities, as in the stand-alone source, requires a tapered structure that gives rise to numerous complications including beam defocusing and manufacturing challenges; approaches for addressing these complications are mentioned.

  9. Experimental investigation of magnetoplasma acceleration of dielectric projectiles in a rail gun

    International Nuclear Information System (INIS)

    Kondratenko, M.M.; Lebedev, E.F.; Ostashev, V.E.; Safonov, V.I.; Fortov, V.E.; Ul'yanov, A.V.

    1988-01-01

    The authors present results of experimental investigations of the process of a nondestructive electrodynamic acceleration of dielectric projectiles in a magnetoplasma accelerator of rail gun type upon discharge of the electrical energy of the capacitor bank. They describe the phenomenon of decay of the plasma driving piston. They describe the causes of this phenomenon and the practical steps to avoid it. In a specific facility regimes have been achieved with electrodynamic acceleration of projectiles without plasma piston decay at working currents of up to 0.7 MA. In acceleration of projectiles of mass ∼ 1 g a speed of 6 km/sec has been attained and reproduced. The facility constructed can be used efficiently in experiments to investigate the thermophysical properties of substances using dynamic methods as a means of creating intense kinetic energy pulses

  10. Thermal radiation of fermions by an accelerated wall

    International Nuclear Information System (INIS)

    Horibe, Minoru

    1979-01-01

    The theory of particle production by an accelerated wall is extended to the massless Dirac particle. It is shown that the mean occupation number of fermions (anti-fermions) is given by the Fermi distribution function. (author)

  11. Experimental and Theoretical Researches of a Resonator Concept of a Dielectric Wakefield Accelerator

    International Nuclear Information System (INIS)

    Onishchenko, I.N.; Kiselev, V.A.; Linnik, A.F.; Onishchenko, N.I.; Sotnikov, G.V.; Uskov, V.V.

    2006-01-01

    Wakefield excitation in a cylindrical dielectric waveguide or resonator by a regular sequence of electron bunches foe application to high-gradient particle acceleration has been investigated theoretically and experimentally using an electron linac 'ALMAZ-2' (4.5 MeV, 6.10 3 bunches of duration 60 ps and charge 0.32 nC each)

  12. Accelerating Dielectrics Design Using Thinking Machines

    Science.gov (United States)

    Ramprasad, R.

    2013-03-01

    High energy density capacitors are required for several pulsed power and energy storage applications, including food preservation, nuclear test simulations, electric propulsion of ships and hybrid electric vehicles. The maximum electrostatic energy that can be stored in a capacitor dielectric is proportional to its dielectric constant and the square of its breakdown field. The current standard material for capacitive energy storage is polypropylene which has a large breakdown field but low dielectric constant. We are involved in a search for new classes of polymers superior to polypropylene using first principles computations combined with statistical and machine learning methods. Essential to this search are schemes to efficiently compute the dielectric constant of polymers and the intrinsic dielectric breakdown field, as well as methods to determine the stable structures of new classes of polymers and strategies to efficiently navigate through the polymer chemical space offered by the periodic table. These methodologies have been combined with statistical learning paradigms in order to make property predictions rapidly, and promising classes of polymeric systems for energy storage applications have been identified. This work is being supported by the Office of Naval Research.

  13. Dependence of optical phase modulation on anchoring strength of dielectric shield wall surfaces in small liquid crystal pixels

    Science.gov (United States)

    Isomae, Yoshitomo; Shibata, Yosei; Ishinabe, Takahiro; Fujikake, Hideo

    2018-03-01

    We demonstrated that the uniform phase modulation in a pixel can be realized by optimizing the anchoring strength on the walls and the wall width in the dielectric shield wall structure, which is the needed pixel structure for realizing a 1-µm-pitch optical phase modulator. The anchoring force degrades the uniformity of the phase modulation in ON-state pixels, but it also keeps liquid crystals from rotating against the leakage of an electric field. We clarified that the optimal wall width and anchoring strength are 250 nm and less than 10-4 J/m2, respectively.

  14. Femtosecond Planar Electron Beam Source for Micron-Scale Dielectric Wake Field Accelerator. Final report

    International Nuclear Information System (INIS)

    Hirshfield, Jay L.

    2006-01-01

    A new accelerator LACARA is under construction at ATF, Brookhaven National Laboratory. LACARA is to be powered by a 1 TW CO2 laser, and will utilize a 6-T 2-m long solenoidal magnetic field. For a 50 MeV injected electron bunch, LACARA is expected to produce a 100 MeV 1 ps gyrating beam with ∼ 3% energy spread. Beam electrons advance in phase at the laser frequency, executing one cycle each 35 fs. A beam stop with a small off-axis channel will transmit a short beam pulse every optical cycle, thereby producing a train of about 30, 3.5 fs, 1-3 pC microbunches for each laser pulse. One application for this train of microbunches obtained from a LACARA-type device involves focusing a portion of the beam using a magnetic quadrupole into a rectangular cross-section having a narrow dimension of a few microns and a height of a few hundred microns. These microbunches may be injected into a planar dielectric-lined waveguide where cumulative buildup of wake fields can lead to an accelerating gradient > 1 GV/m. This proposed vacuum-based wake field structure is mechanically rigid and capable of accurate microfabrication, factors important in staging a large number of accelerator modules. Furthermore, the accelerating gradients it promises are comparable with those for plasma accelerators. A LACARA unit for preparing suitable bunches at 500 MeV is described. Physics issues are discussed including bunch spreading and transport, bunch shaping, aperture radiation, dielectric breakdown, and bunch stability in the rectangular wake field structure. In appendices to this report, three supporting documents are attached. These include a set of drawings that show the layout of the beam line and optical line for LACARA at ATF-BNL; and two reprints of recent articles published in PRST-AB. The first article describes measurements of the coherent superposition of wake fields that arise from a periodic train of bunches, with supporting analysis. The second article presents theory that

  15. Conceptual Design of Dielectric Accelerating Structures for Intense Neutron and Monochromatic X-ray Sources

    Science.gov (United States)

    Blanovsky, Anatoly

    2004-12-01

    Bright compact photon sources, which utilize electron beam interaction with periodic structures, may benefit a broad range of medical, industrial and scientific applications. A class of dielectric-loaded periodic structures for hard and soft X-ray production has been proposed that would provide a high accelerating gradient when excited by an external RF and/or primary electron beam. Target-distributed accelerators (TDA), in which an additional electric field compensates for lost beam energy in internal targets, have been shown to provide the necessary means to drive a high flux subcritical reactor (HFSR) for nuclear waste transmutation. The TDA may also be suitable for positron and nuclear isomer production, X-ray lithography and monochromatic computer tomography. One of the early assumptions of the theory of dielectric wake-field acceleration was that, in electrodynamics, the vector potential was proportional to the scalar potential. The analysis takes into consideration a wide range of TDA design aspects including the wave model of observed phenomena, a layered compound separated by a Van der Waals gap and a compact energy source based on fission electric cells (FEC) with a multistage collector. The FEC is a high-voltage power source that directly converts the kinetic energy of the fission fragments into electrical potential of about 2MV.

  16. Acceleration of electrons at wakefield excitation by a sequence of relativistic electron bunches in dielectric resonator

    International Nuclear Information System (INIS)

    Kiselev, V.A.; Linnik, A.F.; Mirnyj, V.I.; Onishchenko, I.N.; Uskov, V.V.

    2009-01-01

    Method is proposed to divide a regular sequence of electron bunches into parts of bunches driving wakefield and witness bunches, which should be accelerated. It allows to avoid the necessity of additional electron accelerator for witness bunches producing and the necessity of precision short time techniques of injection phase adjusting. The idea concludes to the frequency detuning between bunches repetition frequency and the frequency of the fundamental mode of excited wakefield. Experiments were carried out on the linear resonant accelerator 'Almaz-2', which injected in the dielectric resonator a sequence of 6000 short bunches of relativistic electrons with energy 4.5 MeV, charge 0.16 nC and duration 60 psec each, the repetition interval 360 ps. Frequency detuning was entered by change of frequency of the master generator of the klystron within the limits of one percent so that the phase taper on the length of bunches sequence achieved 2π. Energy spectra of electrons of bunches sequence, which have been propagated through the dielectric resonator are measured and analyzed

  17. Observation of multipactor suppression in a dielectric-loaded accelerating structure using an applied axial magnetic field

    International Nuclear Information System (INIS)

    Jing, C.; Konecny, R.; Antipov, S.; Chang, C.; Gold, S. H.; Schoessow, P.; Kanareykin, A.; Gai, W.

    2013-01-01

    Efforts by a number of institutions to develop a Dielectric-Loaded Accelerating (DLA) structure capable of supporting high gradient acceleration when driven by an external radio frequency source have been ongoing over the past decade. Single surface resonant multipactor has been previously identified as one of the major limitations on the practical application of DLA structures in electron accelerators. In this paper, we report the results of an experiment that demonstrated suppression of multipactor growth in an X-band DLA structure through the use of an applied axial magnetic field. This represents an advance toward the practical use of DLA structures in many accelerator applications

  18. Characteristics of the magnetic wall reflection model on ion acceleration in gas-puff z pinch

    International Nuclear Information System (INIS)

    Nishio, M.; Takasugi, K.

    2013-01-01

    The magnetic wall reflection model was examined with the numerical simulation of the trajectory calculation of particles. This model is for the ions accelerated by some current-independent mechanism. The trajectory calculation showed angle dependency of highest velocities of accelerated particles. This characteristics is of the magnetic wall reflection model, not of the other current-independent acceleration mechanism. Thomson parabola measurements of accelerated ions produced in the gas-puff z-pinch experiments were carried out for the verification of the angle dependency. (author)

  19. Radiation testing of thick-wall objects using a linear accelerator or Co-60

    International Nuclear Information System (INIS)

    Depending on the energy required, a 60 Co source or various types of betatrons and linear accelerators may be used for radiation testing of thick-walled metal parts. While 60 Co sources are easily transported, accelerators are not, but a transportable linear accelerator is described

  20. On the existence of steady flow in a channel with one porous wall or two accelerating walls

    Directory of Open Access Journals (Sweden)

    Chunqing Lu

    1998-11-01

    Full Text Available channel either with no-slip at one wall and constant uniform suction or injection through another wall, or with two accelerating walls. The flows are governed by the fourth order nonlinear differential equation $F^{iv}+R(FF'''-F'F''=0$. In the former case, the flow is subject to the boundary conditions $F(-1=F'(-1=F'(1=0$, $F(1=-1$. In the latter case, the boundary conditions are $F(-1=F(1=0$, $F'(-1=-1$, $F'(1 = 1$.

  1. Optimisation of the electromagnetic matching of manganese dioxide/multi-wall carbon nanotube composites as dielectric microwave-absorbing materials

    International Nuclear Information System (INIS)

    Ting, Tzu-Hao; Chiang, Chih-Chia; Lin, Po-Chuan; Lin, Chia-Huei

    2013-01-01

    An optimised composite sample was prepared using two dielectric materials manganese dioxide (MnO 2 ) and multi-wall carbon nanotubes (MWNTs) in an epoxy-resin matrix. Structural characterisations of both the synthesised manganese dioxide (MnO 2 ) and the multi-wall carbon nanotubes (MWNTs) were performed by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The microwave absorption properties of dielectric composites with different weight fractions of MnO 2 were investigated by measuring the complex permittivity, the complex permeability and the reflection loss in the 2–18 and 18–40 GHz microwave frequency ranges using the free space method. The complex permittivity varied with the MnO 2 content, and the results show that a high concentration of fillers increased the dielectric constant. Therefore, the appropriate combination of components and experimental conditions can produce materials with specific characteristic for use as wide-band microwave absorbers. - Highlights: ► This paper analyses optimised microwave absorption for MnO 2 /MWNT composites. ► Structural characterisations were performed by using XRD and SEM. ► Increasing MnO 2 content enhances the complex permittivity in MnO 2 /MWNT matrix. ► The reflection loss varies with changes content of MnO 2 for required frequency bands

  2. Inspection of piping wall loss with flow accelerated corrosion accelerated simulation test

    International Nuclear Information System (INIS)

    Ryu, Kyung Ha; Kim, Ji Hak; Hwang, Il Soon; Lee, Na Young; Kim, Ji Hyun

    2009-01-01

    Flow Accelerated Corrosion (FAC) has become a hot issue for aging of passive components. Ultrasonic Technique (UT) has been adopted to inspect the secondary piping of Nuclear Power Plants (NPPs). UT, however, uses point detection method, which results in numerous detecting points and thus takes time. We developed an Equipotential Switching Direct Current Potential Drop (ES-DCPD) method to monitor the thickness of piping that covers wide range of piping at once time. Since the ES-DCPD method covers area, not a point, it needs less monitoring time. This can be a good approach to broad carbon steel piping system such as secondary piping of NPPs. In this paper, FAC accelerated simulation test results is described. We realized accelerated FAC phenomenon by 2 times test: 23.7% thinning in 216.7 hours and 51% thinning in 795 hours. These were monitored by ES-DCPD and traditional UT. Some parameters of water chemistry are monitored and controlled to accelerate FAC process. As sensitive factors on FAC, temperature and pH was changed during the test. The wall loss monitored results reflected these changes of water chemistry successfully. Developed electrodes are also applied to simulation loop to monitor water chemistry. (author)

  3. Distributed grating-assisted coupler for optical all-dielectric electron accelerator

    Directory of Open Access Journals (Sweden)

    Zhiyu Zhang

    2005-07-01

    Full Text Available A Bragg waveguide consisting of multiple dielectric layers with alternating index of refraction becomes an excellent option to form electron accelerating structure powered by high power laser sources. It provides confinement of a synchronous speed-of-light mode with extremely low loss. However, laser field cannot be coupled into the structure collinearly with the electron beam. There are three requirements in designing input coupler for a Bragg electron accelerator: side coupling, selective mode excitation, and high coupling efficiency. We present a side-coupling scheme using a distributed grating-assisted coupler to inject the laser power into the waveguide. Side coupling is achieved by a grating with a period on the order of an optical wavelength. The phase matching condition results in resonance coupling thus providing selective mode excitation capability. The coupling efficiency is limited by profile matching between the outgoing beam and the incoming beam, which has normally a Gaussian profile. We demonstrate a nonuniform distributed grating structure generating an outgoing beam with a Gaussian profile, therefore, increasing the coupling efficiency.

  4. Plasma non-uniformity in a symmetric radiofrequency capacitively-coupled reactor with dielectric side-wall: a two dimensional particle-in-cell/Monte Carlo collision simulation

    Science.gov (United States)

    Liu, Yue; Booth, Jean-Paul; Chabert, Pascal

    2018-02-01

    A Cartesian-coordinate two-dimensional electrostatic particle-in-cell/Monte Carlo collision (PIC/MCC) plasma simulation code is presented, including a new treatment of charge balance at dielectric boundaries. It is used to simulate an Ar plasma in a symmetric radiofrequency capacitively-coupled parallel-plate reactor with a thick (3.5 cm) dielectric side-wall. The reactor size (12 cm electrode width, 2.5 cm electrode spacing) and frequency (15 MHz) are such that electromagnetic effects can be ignored. The dielectric side-wall effectively shields the plasma from the enhanced electric field at the powered-grounded electrode junction, which has previously been shown to produce locally enhanced plasma density (Dalvie et al 1993 Appl. Phys. Lett. 62 3207-9 Overzet and Hopkins 1993 Appl. Phys. Lett. 63 2484-6 Boeuf and Pitchford 1995 Phys. Rev. E 51 1376-90). Nevertheless, enhanced electron heating is observed in a region adjacent to the dielectric boundary, leading to maxima in ionization rate, plasma density and ion flux to the electrodes in this region, and not at the reactor centre as would otherwise be expected. The axially-integrated electron power deposition peaks closer to the dielectric edge than the electron density. The electron heating components are derived from the PIC/MCC simulations and show that this enhanced electron heating results from increased Ohmic heating in the axial direction as the electron density decreases towards the side-wall. We investigated the validity of different analytical formulas to estimate the Ohmic heating by comparing them to the PIC results. The widespread assumption that a time-averaged momentum transfer frequency, v m , can be used to estimate the momentum change can cause large errors, since it neglects both phase and amplitude information. Furthermore, the classical relationship between the total electron current and the electric field must be used with caution, particularly close to the dielectric edge where the (neglected

  5. Dielectric-filled radiofrequency linacs

    Energy Technology Data Exchange (ETDEWEB)

    Faehl, R J; Keinigs, R K; Pogue, E W [Los Alamos National Lab., NM (United States)

    1997-12-31

    High current, high brightness electron beam accelerators promise to open up dramatic new applications. Linear induction accelerators are currently viewed as the appropriate technology for these applications. A concept by Humphries and Hwang may permit radiofrequency accelerators to fulfill the same functions with greater simplicity and enhanced flexibility. This concept involves the replacement of vacuum rf cavities with dielectric filled ones. Simple analysis indicates that the resonant frequencies are reduced by a factor of ({epsilon}{sub 0}/{epsilon}){sup 1/2} while the stored energy is increased by {epsilon}/{epsilon}{sub 0}. For a high dielectric constant like water, this factor can approach 80. A series of numerical calculations of simple pill-box cavities was performed. Eigenfunctions and resonant frequencies for a full system configuration, including dielectric material, vacuum beamline, and a ceramic window separating the two have been computed. These calculations are compared with the results of a small experimental cavity which have been constructed and operated. Low power tests show excellent agreement. (author). 4 figs., 8 refs.

  6. Evaluation of wall thinning profile by flow accelerated corrosion in separation and union pipe

    International Nuclear Information System (INIS)

    Watanabe, Shun; Yoneda, Kimitoshi

    2013-01-01

    Flow Accelerated Corrosion (FAC) is a pipe wall thinning phenomena to be monitored and managed in power plants with high priority. At present, its management has been conducted with conservative evaluation of thinning rate and residual lifetime of the piping based on wall thickness measurements. However, noticeable case of wall thinning was occurred at separation and union pipe. In such pipe system, it is a problem to manage section beneath reinforcing plate of T-tube pipe and 'crotch' of T-joint pipe; the region where wall thickness measurement is difficult to conduct with ordinary ultrasonic testing device. In this study, numerical analysis for separation and union part of T-tube and T-joint pipe was conducted, and wall thinning profile by Flow Accelerated Corrosion was evaluated by calculating mass transfer coefficient and geometry factor. Based on these results, we considered applicable wall thinning management for T-tube and T-joint pipe. In the case of union flow from main and branch pipe, the wall thinning profile of T-tube showed the tendency of increase at main pipe like semielliptical region. On the other hand, noticeable profile appeared at 'crotch' in T-joint. Although it was found that geometry factor of T-joint in this case was half the value of T-tube, an alternative evaluation method to previous one might be needed for the profiles of 'semielliptical region' and 'crotch'. (author)

  7. Electrostatic accelerator dielectrics

    International Nuclear Information System (INIS)

    Cooke, C.M.

    1989-05-01

    High voltage insulation problems in electrostatic accelerators are discussed. The aim of the analysis is to broaden the knowledge, highlight the characteristics of insulation technology and design strategies to improve use. The basic geometry of the insulation in accelerators is considered. A detailed description of each of the insulation regions is provided. The gas gap insulation of the terminal voltage is found to be sensitive to regions of high electric stress. In order to obtain satisfactory performance from solid support insulation, the attention is focused on the electric stress value and distribution. Potential subjects for discussion and further investigations are given

  8. Beam dynamics analysis of dielectric laser acceleration using a fast 6D tracking scheme

    Directory of Open Access Journals (Sweden)

    Uwe Niedermayer

    2017-11-01

    Full Text Available A six-dimensional symplectic tracking approach exploiting the periodicity properties of dielectric laser acceleration (DLA gratings is presented. The longitudinal kick is obtained from the spatial Fourier harmonics of the laser field within the structure, and the transverse kicks are obtained using the Panofsky-Wenzel theorem. Additionally to the usual, strictly longitudinally periodic gratings, our approach is also applicable to periodicity chirped (subrelativistic and tilted (deflection gratings. In the limit of small kicks and short periods we obtain the 6D Hamiltonian, which allows, for example, to obtain matched beam distributions in DLAs. The scheme is applied to beam and grating parameters similar to recently performed experiments. The paper concludes with an outlook to laser based focusing schemes, which are promising to overcome fundamental interaction length limitations, in order to build an entire microchip-sized laser driven accelerator.

  9. Experimental study for the use of sulfur hexafluoride as dielectric gas in particle accelerators

    International Nuclear Information System (INIS)

    Candanedo y Bernabe, C.

    1993-01-01

    The sulfur hexafluoride is the better dielectric gas in the world. It is used in particle accelerator, power stations and high voltage transformators. This is a high stable gas, but when is used as dielectric is degraded in toxic and corrosive fluorides this degradation of sulfur hexafluoride is a function of the voltaic arc, crown effect, pressure, temperature and radiation. The purification of the sulfur fluoride permitted to work in safe form and without the risks as contaminant. The objective of the work is the development of a process for the separation of the wastes from the fabrication of sulphur fluoride and the products of degradation. This process used adsorbents when this gas is used as dielectric. The methodology employed was bibliography research, experimental design of the equipment, construction of the experimental equipment, selection and use of adsorbents, installation of the adsorption columns for the experimentation, flow of the sulfur hexafluoride through the adsorbents, searching of the fluoride hexafluoride before and after of the step through the adsorption columns and writing of the results. In base to the results we conclude that the process is good. The work could be advantage using chromatographic techniques with adequate standards. Is possible to extend the study using an additional number of adsorbents. (Author). 34 refs, 7 graphs, 3 tabs

  10. Identification of defect distribution at ferroelectric domain walls from evolution of nonlinear dielectric response during the aging process

    Czech Academy of Sciences Publication Activity Database

    Mokrý, Pavel; Sluka, T.

    2016-01-01

    Roč. 93, č. 6 (2016), č. článku 064114. ISSN 2469-9950 R&D Projects: GA ČR(CZ) GA14-32228S Institutional support: RVO:61389021 Keywords : Nonlinear dielectric response * ferroelectric domain walls * aging process * phase field simulations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.836, year: 2016 http://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.064114

  11. High-gradient compact linear accelerator

    Science.gov (United States)

    Carder, Bruce M.

    1998-01-01

    A high-gradient linear accelerator comprises a solid-state stack in a vacuum of five sets of disc-shaped Blumlein modules each having a center hole through which particles are sequentially accelerated. Each Blumlein module is a sandwich of two outer conductive plates that bracket an inner conductive plate positioned between two dielectric plates with different thicknesses and dielectric constants. A third dielectric core in the shape of a hollow cylinder forms a casing down the series of center holes, and it has a dielectric constant different that the two dielectric plates that sandwich the inner conductive plate. In operation, all the inner conductive plates are charged to the same DC potential relative to the outer conductive plates. Next, all the inner conductive plates are simultaneously shorted to the outer conductive plates at the outer diameters. The signal short will propagate to the inner diameters at two different rates in each Blumlein module. A faster wave propagates quicker to the third dielectric core across the dielectric plates with the closer spacing and lower dielectric constant. When the faster wave reaches the inner extents of the outer and inner conductive plates, it reflects back outward and reverses the field in that segment of the dielectric core. All the field segments in the dielectric core are then in unipolar agreement until the slower wave finally propagates to the third dielectric core across the dielectric plates with the wider spacing and higher dielectric constant. During such unipolar agreement, particles in the core are accelerated with gradients that exceed twenty megavolts per meter.

  12. Dielectric properties of vertically aligned multi-walled carbon nanotubes in the terahertz and mid-infrared range

    Science.gov (United States)

    Thomson, Mark D.; Zouaghi, Wissem; Meng, Fanqi; Wiecha, Matthias M.; Rabia, Kaneez; Heinlein, Thorsten; Hussein, Laith; Babu, Deepu; Yadav, Sandeep; Engstler, Jörg; Schneider, Jörg J.; Nicoloso, Norbert; Rychetský, Ivan; Kužel, Petr; Roskos, Hartmut G.

    2018-01-01

    We investigate the broadband dielectric properties of vertically aligned, multi-wall carbon nanotubes (VACNT), over both the terahertz (THz) and mid-infrared spectral ranges. The nominally undoped, metallic VACNT samples are probed at normal incidence, i.e. the response is predominantly due to polarisation perpendicular to the CNT axis. A detailed comparison of various conductivity models and previously reported results is presented for the non-Drude behaviour we observe in the conventional THz range (up to 2.5 THz). Extension to the mid-infrared range reveals an absorption peak at \

  13. Calculation of longitudinal and transverse wake-field effects in dielectric structures

    International Nuclear Information System (INIS)

    Gai, W.

    1989-01-01

    The electro-magnetic radiation of a charged particle passing through a dielectric structure has many applications to accelerator physics. Recently a new acceleration scheme, called the dielectric wake field accelerator, has been proposed. It also can be used as a pick up system for a storage ring because of its slow wave characteristics. In order to study these effects in detail, in this paper we will calculate the wake field effects produced in a dielectric structure by a charged particle. 8 refs., 2 figs

  14. ELECTROMAGNETIC AND THERMAL SIMULATIONS FOR THE SWITCH REGION OF A COMPACT PROTON ACCELERATOR

    International Nuclear Information System (INIS)

    Wang, L; Caporaso, G J; Sullivan, J S

    2007-01-01

    A compact proton accelerator for medical applications is being developed at Lawrence Livermore National Laboratory. The accelerator architecture is based on the dielectric wall accelerator (DWA) concept. One critical area to consider is the switch region. Electric field simulations and thermal calculations of the switch area were performed to help determine the operating limits of rmed SiC switches. Different geometries were considered for the field simulation including the shape of the thin Indium solder meniscus between the electrodes and SiC. Electric field simulations were also utilized to demonstrate how the field stress could be reduced. Both transient and steady steady-state thermal simulations were analyzed to find the average power capability of the switches

  15. Construction of electron accelerator for studying secondary emission in dielectric materials

    International Nuclear Information System (INIS)

    Hessel, R.

    1990-01-01

    An acelerator for the generation of low energy electrons (in the 0.4 to 20 keV range) was constructed. The accelerator is equipped with some devices especially designed for the investigation of the electrical properties of electron-irradiated dielectrics. In this work we have employed it for the study of the secondary electron emission of irradiated polymers. Reference is made to a method proposed by H. von Seggern (IEEE Trans. Nucl. Sci. NS-32, p.1503 (1985)] which was intended for the determination of the electron emission yield especially between the two cross-over points in a single run, here called the dynamical method. We have been able to prove that, contrary to expectation, this method does not give correct results over the entire emission curve. Rather it gives yield values which are too low by 25% in the region where the emission exhibits a maximum, due to the interaction between the electron emission process and the positive surface charge of the dielectric. However the method needs not to be dismissed entirely. As it is, it can be used advantageously for the precise determination of the energy of the second cross-over point. In addition, with the same set up, the method could be improved by replacing the continuous irradiation of the sample by a pulsed irradiation, leading to results essentially the same as those shown in the literature. Finally analysing the process of interaction between the positive charge of the dielectric and the mechanism of electron emission in several situations, we were able: I) to determine the maximum value and the average value of the escape depth of the emitted electrons; II) for a sample with a net positive charge, to show that the positive charge resides very near the surface of incidence; III) for a sample with a net negative charge, to show that the positive charge also resides near the surface while the (prevalent) negative charge resides in the bulk of the material. (author)

  16. Study on the Microwave Permittivity of Single-Walled Carbon Nanotube

    Science.gov (United States)

    Liu, Xiaolai; Zhao, Donglin

    2009-01-01

    In this article, we studied the microwave permittivity of the complex of the single-walled carbon nanotube and paraffin in 2-18GHz. In the range, the dielectric loss of single-walled carbon nanotube is higher, and the real part and the imaginary part of the dielectric constant decrease with the increase of frequency, and the dielectric constant…

  17. Collective field accelerator

    International Nuclear Information System (INIS)

    Luce, J.S.

    1978-01-01

    A collective field accelerator which operates with a vacuum diode and utilizes a grooved cathode and a dielectric anode that operates with a relativistic electron beam with a ν/γ of approx. 1, and a plurality of dielectric lenses having an axial magnetic field thereabout to focus the collectively accelerated electrons and ions which are ejected from the anode. The anode and lenses operate as unoptimized r-f cavities which modulate and focus the beam

  18. Dielectric properties of PMMA/Soot nanocomposites.

    Science.gov (United States)

    Clayton, Lanetra M; Cinke, Martin; Meyyappan, M; Harmon, Julie P

    2007-07-01

    Dielectric analysis (DEA) of relaxation behavior in poly(methyl methacrylate) (PMMA) soot nanocomposites is described herein. The soot, an inexpensive material, consists of carbon nanotubes, amorphous and graphitic carbon and metal particles. Results are compared to earlier studies on PMMA/multi-walled nanotube (MWNT) composites and PMMA/single-walled nanotube (SWNT) composites. The beta relaxation process appeared to be unaffected by the presence of the soot, as was noted earlier in nanotube composites. The gamma relaxation region in PMMA, normally dielectrically inactive, was "awakened" in the PMMA/soot composite. This occurrence is consistent with previously published data on nanotube composites. The dielectric permittivity, s', increased with soot content. The sample with 1% soot exhibited a permittivity (at 100 Hz and 25 degrees C) of 7.3 as compared to 5.1 for neat PMMA. Soot increased the dielectric strength, deltaE, of the composites. The 1% soot sample exhibited a dielectric strength of 6.38, while the neat PMMA had a value of 2.95 at 40 degrees C. The symmetric broadening term (alpha) was slightly higher for the 1% composite at temperatures near the secondary relaxation and near the primary relaxation, but all samples deviated from symmetrical semi-circular behavior (alpha = 1). The impact of the soot filler is seen more clearly in dielectric properties than in mechanical properties studies conducted earlier.

  19. Particle-in-cell simulation for the effect of segmented electrodes near the exit of an aton-type Hall thruster on ion focusing acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Yu, D.R.; Qing, S.W.; Liu, H.; Li, H. [Lab. of Plasma Propulsion, Harbin Institute of Technology (China)

    2011-12-15

    The effect of floating conductive electrodes near the channel exit of an Aton-type Hall thruster on ion focusing acceleration is studied by simulating the two-dimensional plasma flow with a fully kinetic Particle-in-Cell method for the gas flow rate j{sub a} ranged in 1{proportional_to}3 mg/s. Numerical results show that low-emissive electrodes can reduce plume divergence if the electrode length is less than 2 mm due to the low secondary electron emissive characteristic, but widen plume in all the gas flow rate range if the electrode length is greater than 2mm since the conductive property of segmented electrodes trends to make equipotential lines convex toward channel exit and is even parallel to the wall surface in the near-wall region. Further investigation predicts that the combination of high emissive dielectric wall and segmented low-emissive dielectric wall is a promising way to reduce plume divergence (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Absorptive reduction and width narrowing in λ-type atoms confined between two dielectric walls

    International Nuclear Information System (INIS)

    Li Yuanyuan; Hou Xun; Bai Jintao; Yan Junfeng; Gan Chenli; Zhang Yanpeng

    2008-01-01

    This paper investigates the absorptive reduction and the width narrowing of electromagnetically induced transparency (EIT) in a thin vapour film of λ-type atoms confined between two dielectric walls whose thickness is comparable with the wavelength of the probe field. The absorptive lines of the weak probe field exhibit strong reductions and very narrow EIT dips, which mainly results from the velocity slow-down effects and transient behaviour of atoms in a confined system. It is also shown that the lines are modified by the strength of the coupling field and the ratio of L/λ, with L the film thickness and λ the wavelength of the probe field. A simple robust recipe for EIT in a thin medium is achievable in experiment. (general)

  1. Systems and methods of varying charged particle beam spot size

    Science.gov (United States)

    Chen, Yu-Jiuan

    2014-09-02

    Methods and devices enable shaping of a charged particle beam. A modified dielectric wall accelerator includes a high gradient lens section and a main section. The high gradient lens section can be dynamically adjusted to establish the desired electric fields to minimize undesirable transverse defocusing fields at the entrance to the dielectric wall accelerator. Once a baseline setting with desirable output beam characteristic is established, the output beam can be dynamically modified to vary the output beam characteristics. The output beam can be modified by slightly adjusting the electric fields established across different sections of the modified dielectric wall accelerator. Additional control over the shape of the output beam can be excreted by introducing intentional timing de-synchronization offsets and producing an injected beam that is not fully matched to the entrance of the modified dielectric accelerator.

  2. Soft X-ray reflectivity: from quasi-perfect mirrors to accelerator walls

    CERN Document Server

    Schäfers, F.

    2013-04-22

    Reflection of light from surfaces is a very common, but complex phenomenon not only in science and technology, but in every day life. The underlying basic optical principles have been developed within the last five centuries using visible light available from the sun or other laboratory light sources. X-rays were detected in 1895, and the full potential of soft- and hard-x ray radiation as a probe for the electronic and geometric properties of matter, for material analysis and its characterisation is available only since the advent of synchrotron radiation sources some 50 years ago. On the other hand high-brilliance and high power synchrotron radiation of present-days 3rd and 4th generation light sources is not always beneficial. Highenergy machines and accelerator-based light sources can suffer from a serious performance drop or limitations due to interaction of the synchrotron radiation with the accelerator walls, thus producing clouds of photoelectrons (e-cloud) which in turn interact with the accelerated ...

  3. Assessment of fluctuating pressure gradient using acceleration spectra in near wall flows

    Science.gov (United States)

    Cadel, Daniel; Lowe, K. Todd

    2015-11-01

    Separation of contributions to the fluctuating acceleration from pressure gradient fluctuations and viscous shear fluctuations in the frequency domain is examined in a turbulent boundary layer. Past work leveraging turbulent accelerations for pressure gradient measurements has neglected the viscous shear term from the momentum equation--an invalid assumption in the case of near wall flows. The present study seeks to account for the influence of the viscous shear term and spectrally reject its contribution, which is thought to be concentrated at higher frequencies. Spectra of velocity and acceleration fluctuations in a flat plate, zero pressure gradient turbulent boundary layer at a momentum thickness Reynolds number of 7500 are measured using a spatially resolving three-component laser Doppler velocimeter. This canonical case data is applied for validation of the spectral approach for future application in more complex aerodynamic flows.

  4. RF cavity using liquid dielectric for tuning and cooling

    Science.gov (United States)

    Popovic, Milorad [Warrenville, IL; Johnson, Rolland P [Newport News, VA

    2012-04-17

    A system for accelerating particles includes an RF cavity that contains a ferrite core and a liquid dielectric. Characteristics of the ferrite core and the liquid dielectric, among other factors, determine the resonant frequency of the RF cavity. The liquid dielectric is circulated to cool the ferrite core during the operation of the system.

  5. Laser-driven electron accelerators

    International Nuclear Information System (INIS)

    Palmer, R.B.

    1981-01-01

    The following possibilities are discussed: inverse free electron laser (wiggler accelerator); inverse Cerenkov effect; plasma accelerator; dielectric tube; and grating linac. Of these, the grating acceleraton is considered the most attractive alternative

  6. Accelerating field step-up transformer in wake-field accelerators

    International Nuclear Information System (INIS)

    Chojnacki, E.; Gai, W.; Schoessow, P.; Simpson, J.

    1991-01-01

    In the wake-field scheme of particle acceleration, a short, intense drive bunch of electrons passes through a slow-wave structure, leaving behind high rf power in its wake field. The axial accelerating electric field associated with the rf can be quite large, > 100 MeV/m, and is used to accelerate a much less intense ''witness'' beam to eventual energies > 1 TeV. The rf power is deposited predominantly in the fundamental mode of the structure, which, for dielectric-lined waveguide as used at Argonne, is the TM 01 mode. In all likelihood on the field amplitude will be limited only by rf breakdown of the dielectric material, the limit of which is currently unknown in the short time duration, high frequency regime of wake-field acceleration operation. To obtain such strong electric fields with given wake-field rf power, the dimensions of the dielectric-lined waveguide have to be fairly small, OD of the order of a cm and ID of a few mm, and this gives rise to the generation of strong deflection modes with beam misalignment. While a scheme exists to damp such deflection modes on a bunch-to-bunch time scale, head-tail beam deflection could still be a problem and BNS damping as well as FODO focusing are incomplete cures. Presented here are details of a scheme by which the rf power is generated by in a large-diameter wake-field tube, where deflection mode generation by the intense drive beam is tolerable, and then fed into a small-diameter acceleration tube where the less intense witness beam is accelerated by the greatly enhanced axial electric field. The witness beam generates little deflection-mode power itself, even in the small acceleration tube, thus a final high-quality, high-energy electron beam is produced

  7. An asymmetric emittance electron source for the GALAXIE dielectric-laser accelerator injector

    Energy Technology Data Exchange (ETDEWEB)

    Valloni, A.; Cahill, A.; Fukusawa, A.; Musumeci, P.; Spataro, B.; Yakub, A.; Rosenzweig, J. B. [Dept. of Physics and Astronomy, University of California, Los Angeles, 405 Hilgard Ave., Los Angeles, CA 90034 (United States); Accelerator Division, Laboratori Nazionali di Frascati (INFN-LNF), Via E. Fermi 40, Frascati (RM) 00044 (Italy); Dept. of Physics and Astronomy, University of California, Los Angeles, 405 Hilgard Ave., Los Angeles, CA 90034 (United States)

    2012-12-21

    The GALAXIE project is a program to develop an all-optical, very high field accelerator and undulator integrated SASE FEL system based on dielectric laser-excited structures that support >GV/m fields. These structures are very wide in one direction to allow adequate charge given beam loading considerations, but also having small (subwavelength) apertures in the narrow direction. Such small vertical dimensions yield strict restrictions on the emittance in this direction, while no such constraint exists in the wide transverse direction. However, the overall beam brightness is restricted by the performance requirements on the FEL. To meet these demands, we are studying a very high field gun with a magnetized cathode, yielding a beam with angular momentum content. This beam is then subject to a skew-quad triplet that splits the emittances; this process is reversed to give a round beam after acceleration. This symmetric emittance beam avoids gain-degrading multiple-transverse-mode operation of the FEL, which also demands that the effects of the angular momentum in the beam be mitigated. In this paper we discuss the RF design of an X-band gun to be operated at {approx}200 MV/m peak field giving a 1 pC magnetized beam with unprecedented brightness. We examine the design of the focusing and skew-quad systems, investigating the associated beam dynamics and efficacy of emittance splitting.

  8. Dispersion relation and electron acceleration in the combined circular and elliptical metallic-dielectric waveguide filled by plasma

    Science.gov (United States)

    Abdoli-Arani, A.; Montazeri, M. M.

    2018-04-01

    Two special types of metallic waveguide having dielectric cladding and plasma core including the combined circular and elliptical structure are studied. Longitudinal and transverse field components in the different regions are obtained. Applying the boundary conditions, dispersion relations of the electromagnetic waves in the structures are obtained and then plotted. The acceleration of an injected external relativistic electron in the considered waveguides is studied. The obtained differential equations related to electron motion are solved by the fourth-order Runge-Kutta method. Numerical computations are made, and the results are graphically presented.

  9. Numerical and Experimental Study on Confinement in Y-Shaped Post Wall Branching Waveguide

    Directory of Open Access Journals (Sweden)

    Hiroshi Maeda

    2014-01-01

    Full Text Available Post wall waveguides consist of dielectric or metallic cylinders for microwave around 4 GHz were experimentally and numerically investigated. The structure attracts interests for application of transmission circuit for three-dimensionally integrated planar circuit in millimeter wavelength. In straight waveguide with dielectric cylinders, confinement of microwave is poor, when the post wall was composed of a pair of single row of cylinders. The confinement was improved as increase of rows of post wall. In metallic cylinders, microwave was well confined even when a pair of single row of cylinders composed the waveguide. After confirming confinement of the electromagnetic field, Y-shaped branches of post wall waveguide consisted of dielectric cylinders for microwave were similarly investigated for dielectric rods. The confinement was also improved by increase of post wall up to 3 layers. These results are applicable for fundamental design and fabrication of integrated circuit for microwave and millimeter wave.

  10. One-dimensional Fermi accelerator model with moving wall described by a nonlinear van der Pol oscillator.

    Science.gov (United States)

    Botari, Tiago; Leonel, Edson D

    2013-01-01

    A modification of the one-dimensional Fermi accelerator model is considered in this work. The dynamics of a classical particle of mass m, confined to bounce elastically between two rigid walls where one is described by a nonlinear van der Pol type oscillator while the other one is fixed, working as a reinjection mechanism of the particle for a next collision, is carefully made by the use of a two-dimensional nonlinear mapping. Two cases are considered: (i) the situation where the particle has mass negligible as compared to the mass of the moving wall and does not affect the motion of it; and (ii) the case where collisions of the particle do affect the movement of the moving wall. For case (i) the phase space is of mixed type leading us to observe a scaling of the average velocity as a function of the parameter (χ) controlling the nonlinearity of the moving wall. For large χ, a diffusion on the velocity is observed leading to the conclusion that Fermi acceleration is taking place. On the other hand, for case (ii), the motion of the moving wall is affected by collisions with the particle. However, due to the properties of the van der Pol oscillator, the moving wall relaxes again to a limit cycle. Such kind of motion absorbs part of the energy of the particle leading to a suppression of the unlimited energy gain as observed in case (i). The phase space shows a set of attractors of different periods whose basin of attraction has a complicated organization.

  11. Properties of dielectric barrier discharges in different arrangements

    International Nuclear Information System (INIS)

    Pietsch, G.J.

    2001-01-01

    Dielectric barrier discharges (DBDs) occur in arrangements where at least one dielectric is positioned in a gas space in between conducting electrodes. When breakdown field strength is reached in such a device, charge carriers are created in the gas region, accelerated, multiplied and finally collected on the surface(s) of the dielectric(s). The charge accumulation on the dielectric creates a counter field to that resulting from the power supply and as all of these processes are rather fast, the discharge quenches rapidly. The dielectric has two tasks, it limits the transferred charge and by this the energy conversion and distributes the discharge over the electrode area. That is why DBDs are non-thermal discharges which exist even at atmospheric pressure

  12. Wakefield accelerator with hybrid plasma-dielectric structure of rectangular cross-section

    International Nuclear Information System (INIS)

    Kiselev, V.A.; Linnik, A.F.; Mirnyj, V.I.; Onishchenko, I.N.; Uskov, V.V.

    2010-01-01

    Increase of wakefield intensity at its excitation by a long train of relativistic electron bunches in the rectangular dielectric structure when it is filled with plasma of resonant density was experimentally observed. The first portion of the bunches, produced by electron linac 'Almaz-2', ionizes gas at atmospheric pressure so that plasma frequency becomes equal to bunch repetition frequency and to the frequency of principal Eigen mode of the dielectric structure. Excitation enhancement at such resonant conditions is being studied taking into account the improvement of bunch train propagation in the transit channel caused by charge compensation with plasma and the electrodynamics change of the dielectric structure at filling with plasma.

  13. Summary of SLAC's SEY Measurement On Flat Accelerator Wall Materials

    Energy Technology Data Exchange (ETDEWEB)

    Le Pimpec, F.; /PSI, Villigen /SLAC

    2007-06-08

    The electron cloud effect (ECE) causes beam instabilities in accelerator structures with intense positively charged bunched beams. Reduction of the secondary electron yield (SEY) of the beam pipe inner wall is effective in controlling cloud formation. We summarize SEY results obtained from flat TiN, TiZrV and Al surfaces carried out in a laboratory environment. SEY was measured after thermal conditioning, as well as after low energy, less than 300 eV, particle exposure.

  14. Surfaces electrons at dielectric plasma walls

    International Nuclear Information System (INIS)

    Heinisch, Rafael Leslie

    2013-01-01

    The concept of the electron surface layer introduced in this thesis provides a framework for the description of the microphysics of the surplus electrons immediately at the wall and thereby complements the modelling of the plasma sheath. In this work we have considered from a surface physics perspective the distribution and build-up of an electron adsorbate on the wall as well as the effect of the negative charge on the scattering of light by a spherical particle immersed in a plasma. In our electron surface layer model we treat the wall-bound electrons as a wall-thermalised electron distribution minimising the grand canonical potential and satisfying Poisson's equation. The boundary between the electron surface layer and the plasma sheath is determined by a force balance between the attractive image potential and the repulsive sheath potential and lies in front of the crystallographic interface. Depending on the electron affinity χ, that is the offset of the conduction band minimum to the potential in front of the surface, two scenarios for the wall-bound electrons are realised. For χ 0 electrons penetrate into the conduction band where they form an extended space charge. These different scenarios are also reflected in the electron kinetics at the wall which control the sticking coefficient and the desorption time. If χ -3 . For χ>0 electron physisorption takes place in the conduction band. For this case sticking coefficients and desorption times have not been calculated yet but in view of the more efficient scattering with bulk phonons, responsible for electron energy relaxation in this case, we expect them to be larger than for the case of χ 0 the electrons in the bulk of the particle modify the refractive index through their bulk electrical conductivity. In both cases the conductivity is limited by scattering with surface or bulk phonons. Surplus electrons lead to an increase of absorption at low frequencies and, most notably, to a blue-shift of an

  15. Organic dielectrics in high voltage cables

    Energy Technology Data Exchange (ETDEWEB)

    Vermeer, J

    1962-03-01

    It appears that the limit has been reached in the applicability of oil-impregnated paper as the dielectric for ehv cables, as with rising voltages the prevention of conductor losses becomes increasingly difficult, while the dielectric losses of the insulation, increasing as the square of the voltage, contribute to a greater extent to the temperature rise of the conductor. The power transmitting capacity of ehv cables reaches a maximum at 500 to 600 kV for these reasons. Apart from artificial cooling, a substantial improvement can be obtained only with the use of insulating materials with much lower dielectric losses; these can moreover be applied with a smaller wall thickness, but this means higher field strengths. Synthetic polymer materials meet these requirements but can be used successfully only in the form of lapped film tapes impregnated with suitable liquids. The electrical properties of these heterogeneous dielectrics, in particular, their impulse breakdown strengths are studied in detail.

  16. Dependence of the Casimir-Polder interaction between an atom and a cavity wall on atomic and material properties

    International Nuclear Information System (INIS)

    Mostepanenko, V M; Babb, J F; Caride, A O; Klimchitskaya, G L; Zanette, S I

    2006-01-01

    The Casimir-Polder and van der Waals interactions between an atom and a flat cavity wall are investigated under the influence of real conditions including the dynamic polarizability of the atom, actual conductivity of the wall material and nonzero temperature of the wall. The cases of different atoms near metal and dielectric walls are considered. It is shown that to obtain accurate results for the atom-wall interaction at short separations, one should use the complete tabulated optical data for the complex refractive index of the wall material and the accurate dynamic polarizability of an atom. At relatively large separations in the case of a metal wall, one may use the plasma model dielectric function to describe the dielectric properties of the wall material. The obtained results are important for the theoretical interpretation of experiments on quantum reflection and Bose-Einstein condensation

  17. Railgun-type two step accelerator

    International Nuclear Information System (INIS)

    Kasai, Satoshi; Maeda, Hikosuke; Onozuka, Masanori; Oda, Yasutsugu; Azuma, Kingo.

    1995-01-01

    In the two step-type railgun accelerator used in an experimental nuclear fusion device of the present invention, energy of laser beams to be irradiated in an acceleration gas behind a flying object can be reduced, and the voltage applied between the rails can be lowered. Charged particles are generated and supplied to the acceleration gas behind the flying object by a charged particle generating and supplying device so as to promote generation of plasmas caused by irradiation of laser beams. As a result, dielectric break down is caused between the rails by a Paschen's law by application of voltage lower than dielectric breakdown voltage, thereby enabling to generate plasmas easily. Accordingly, the energy of laser beams can be suppressed and the voltage applied between the rails can be lowered. (I.S.)

  18. Railgun-type two step accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Kasai, Satoshi; Maeda, Hikosuke [Japan Atomic Energy Research Inst., Tokyo (Japan); Onozuka, Masanori; Oda, Yasutsugu; Azuma, Kingo

    1995-10-13

    In the two step-type railgun accelerator used in an experimental nuclear fusion device of the present invention, energy of laser beams to be irradiated in an acceleration gas behind a flying object can be reduced, and the voltage applied between the rails can be lowered. Charged particles are generated and supplied to the acceleration gas behind the flying object by a charged particle generating and supplying device so as to promote generation of plasmas caused by irradiation of laser beams. As a result, dielectric break down is caused between the rails by a Paschen`s law by application of voltage lower than dielectric breakdown voltage, thereby enabling to generate plasmas easily. Accordingly, the energy of laser beams can be suppressed and the voltage applied between the rails can be lowered. (I.S.).

  19. Dielectric properties of lanthanum gallate (LaGaO3) crystal

    Science.gov (United States)

    Dube, D. C.; Scheel, H. J.; Reaney, I.; Daglish, M.; Setter, N.

    1994-04-01

    Dielectric properties of single crystals of LaGaO3 have been measured at low frequencies as well as in the microwave region over a wide temperature range. Measurements performed on two crystal orientations, viz. (001) and (110), show dielectric anomalies at a transition near 145 °C. Dielectric anisotropy below, but not above, 145 °C confirm the previously reported orthorhombic symmetry at room temperature and rhombohedral symmetry above 145 °C. Domain wall motion which arises as a result of a phase transition has been observed around 145 °C.

  20. Investigation of Vacuum Insulator Surface Dielectric Strength with Nanosecond Pulses

    International Nuclear Information System (INIS)

    Nunnally, W.C.; Krogh, M.; Williams, C.; Trimble, D.; Sampayan, S.; Caporaso, G.

    2003-01-01

    The maximum vacuum insulator surface dielectric strength determines the acceleration electric field gradient possible in a short pulse accelerator. Previous work has indicated that higher electric field strengths along the insulator-vacuum interface might be obtained as the pulse duration is decreased. In this work, a 250 kV, single ns wide impulse source was applied to small diameter, segmented insulators samples in a vacuum to evaluate the multi-layer surface dielectric strength of the sample construction. Resonances in the low inductance test geometry were used to obtain unipolar, pulsed electric fields in excess of 100 MV/m on the insulator surface. The sample construction, experimental arrangement and experimental results are presented for the initial data in this work. Modeling of the multi-layer structure is discussed and methods of improving insulator surface dielectric strength in a vacuum are proposed

  1. Review of Acceleration Methods for Seismic Analysis of Through-Wall Cracked Piping from the Viewpoint of Linear Elastic Fracture Mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong Sung; Kim, Yong Woo [Sunchon National University, Suncheon (Korea, Republic of)

    2014-10-15

    Two acceleration methods, an effective force method (or inertia method) and a large mass method, have been applied for performing time history seismic analysis. The acceleration methods for uncracked structures have been verified via previous studies. However, no study has identified the validity of these acceleration methods for cracked piping. In this study, the validity of the acceleration methods for through-wall cracked piping is assessed via time history implicit dynamic elastic seismic analysis from the viewpoint of linear elastic fracture mechanics. As a result, it is identified that both acceleration methods show the same results for cracked piping if a large mass magnitude and maximum time increment are adequately selected.

  2. Review of Acceleration Methods for Seismic Analysis of Through-Wall Cracked Piping from the Viewpoint of Linear Elastic Fracture Mechanics

    International Nuclear Information System (INIS)

    Kim, Jong Sung; Kim, Yong Woo

    2014-01-01

    Two acceleration methods, an effective force method (or inertia method) and a large mass method, have been applied for performing time history seismic analysis. The acceleration methods for uncracked structures have been verified via previous studies. However, no study has identified the validity of these acceleration methods for cracked piping. In this study, the validity of the acceleration methods for through-wall cracked piping is assessed via time history implicit dynamic elastic seismic analysis from the viewpoint of linear elastic fracture mechanics. As a result, it is identified that both acceleration methods show the same results for cracked piping if a large mass magnitude and maximum time increment are adequately selected

  3. Electron injection and acceleration in the plasma bubble regime driven by an ultraintense laser pulse combined with using dense-plasma wall and block

    Science.gov (United States)

    Zhao, Xue-Yan; Xie, Bai-Song; Wu, Hai-Cheng; Zhang, Shan; Hong, Xue-Ren; Aimidula, Aimierding

    2012-03-01

    An optimizing and alternative scheme for electron injection and acceleration in the wake bubble driven by an ultraintense laser pulse is presented. In this scheme, the dense-plasma wall with an inner diameter matching the expected bubble size is placed along laser propagation direction. Meanwhile, a dense-plasma block dense-plasma is adhered inward transversely at some certain position of the wall. Particle-in-cell simulations are performed, which demonstrate that the block plays an important role in the first electron injection and acceleration. The result shows that a collimated electron bunch with a total number of about 4.04×108μm-1 can be generated and accelerated stably to 1.61 GeV peak energy with 2.6% energy spread. The block contributes about 50% to the accelerated electron injection bunch by tracing and sorting statistically the source.

  4. Longitudinal- and transverse-wake-field effects in dielectric structures

    International Nuclear Information System (INIS)

    Rosing, M.; Gai, W.

    1990-01-01

    A dielectric-loaded circular waveguide structure is a potential high-gradient linear wake-field accelerator. A complete solution is given for the longitudinal electric and magnetic fields excited by a δ function and a Gaussian charge distribution moving parallel to the guide axis. The fields are then given in the limit of particle velocity equal to the speed of light. Example calculations are given for a structure with inner radius of 2 mm, outer radius of 5 mm, dielectric constant of 3, and total charge of 100 nC. Peak wake fields in excess of 200 MV/m are found. Azimuthal modes 0 and 1 are investigated for the particular interest of acceleration and deflection problems

  5. Effects of N2O plasma treatment on perhydropolysilazane spin-on-dielectrics for inter-layer-dielectric applications

    International Nuclear Information System (INIS)

    Park, Kyoung-Seok; Ko, Pil-Seok; Kim, Sam-Dong

    2014-01-01

    Effects of the N 2 O plasma treatment (PT) on perhydropolysilazane spin-on-dielectric (PHPS SOD) were examined as potential inter-layer-dielectrics (ILDs) for sub-30 nm Si circuits. The spin-coated PHPS (18.5 wt.%) ILD layers converted at 650 °C were integrated with the 0.18 μm Si front-end-of-the line process. A modified contact pre-cleaning scheme using N 2 O PT produced more uniform and stable contact chain resistances from the SOD ILDs than the case of pre-cleaning only by buffered oxide etcher. Our analysis shows that this enhancement is due to the minimized carbon contamination on the PHPS side-wall surface densified by PT. - Highlights: • Perhydropolysilazane (PHPS) layer is evaluated as a Si interlayer dielectric. • Examine effects of the N 2 O plasma treatment (PT) on PHPS spin-on-dielectrics (SODs) • Significantly improved metal contact resistances are achieved using the N 2 O PT. • Contact resistance enhancement by PT is due to the minimized carbon contamination

  6. Present status on the ion collective acceleration and high-current beam transport in the Lebedev's Physical Institute USSR

    International Nuclear Information System (INIS)

    Kolomenskij, A.A.

    1982-01-01

    The results of investigations into the ion collective acceleration and transport of high-current electron beams (HCEB) in vacuum channels with dielectric walls (VCDW) are presented. The physical principle of transport is in the partial neutralization of spatial charge of electrons with ions escaped from the prewall plasma and the compression of the beam with its own magnetic field. A problem of obtaining the intensive beams of negative ions in diode with magnetic isolation is considered. The mechanism of ion acceleration in VCDW is considered. It is shown that there are two regions with different mechanisms of acceleration. In the first region (''plasma'') ion acceleration in the quasipotential HCEB field up to energy of the order of the electron energy takes place. In the second region (''beam'') the acceleration takes place in the wave fields that can be excited due to the mechanism of the two-beam type instability. The mechanism of ion acceleration in direct electron beams is considered. This mechanism is based on the concept of relaxation oscillations of the virtual cathode and corresponding the reconstruction of the spatial charge distribution

  7. A study on the calculation of the shielding wall thickness in medical linear accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dong Yeon [Dept. of Radiation Oncology, Dongnam Ins. of Radiological and Medical Science, Busan (Korea, Republic of); Park, Eun Tae [Dept. of Radiation Oncology, Inje University Busan Paik Hospital, Busan (Korea, Republic of); Kim, Jung Hoon [Dept. of Radiological science, college of health sciences, Catholic University of Pusan, Busan (Korea, Republic of)

    2017-06-15

    The purpose of this study is to calculate the thickness of shielding for concrete which is mainly used for radiation shielding and study of the walls constructed to shield medical linear accelerator. The optimal shielding thickness was calculated using MCNPX(Ver.2.5.0) for 10 MV of photon beam energy generated by linear accelerator. As a result, the TVL for photon shielding was formed at 50⁓100 cm for pure concrete and concrete with Boron+polyethylene at 80⁓100 cm. The neutron shielding was calculated 100⁓140 cm for pure concrete and concrete with Boron+polyethylene at 90⁓100 cm. Based on this study, the concrete is considered to be most efficient method of using steel plates and adding Boron+polyethylene th the concrete.

  8. Local effects in flow-accelerated corrosion wall thinning

    International Nuclear Information System (INIS)

    Pietralik, J.

    2006-01-01

    'Full text:' There is enough evidence that flow conditions play the dominant role locally in Flow-Accelerated Corrosion (FAC) under certain conditions, e.g., in CANDU feeders. While chemistry and materials set the overall potential for FAC, which can be low or high, flow conditions determine the local distribution of wall thinning. This relationship is not new and recent accurate measurements of FAC rate of a plant feeder bend confirm that the relationship between flow local conditions expressed by local mass transfer coefficient and FAC rate in CANDU feeder bends is close. There is also a lot of other direct and indirect, experimental and laboratory evidence about this relationship. This knowledge can be useful for minimizing inspection, predicting new locations for inspection, predicting the location with the highest FAC rate for a given piping component, e.g., feeder element, and determining what components or feeders and to what extent they should be replaced. It applies also to heat exchangers and steam generators. The objective of this paper is to examine the relationship between FAC rate and local flow parameters. For FAC, the most important flow parameter is mass transfer coefficient. The mass transfer coefficient describes the intensity of the transport of corrosion products from the oxide-water interface into the bulk water. Therefore, this parameter can be used for predicting the local distribution of FAC rate. It could also be used in planning experiments because time-varying surface roughness can explain the time-dependence of FAC rates. The paper presents plant and laboratory evidence about the relationship. In addition, it shows correlations for mass transfer coefficient in components that are highly susceptible to FAC. The role of surface roughness, wall shear stress, and local turbulence is also discussed. (author)

  9. Screening method for piping wall loss by flow accelerated corrosion

    International Nuclear Information System (INIS)

    Ryu, Kyung Ha; Hwang, Il Soon; Lee, Na Young; Oh, Young Jin; Kim, Ji Hyun; Park, Jin Ho; Sohn, Chang Ho

    2008-01-01

    Flow accelerated corrosion (FAC) phenomenon has persisted its impact on plant reliability and personnel safety. Unless we change the operation condition drastically, most parameters affecting FAC will not be effectively controlled. In order to help expand piping inspection coverage, we have developed a screening approach to monitor the wall thinning by direct current potential drop (DCPD) technique. To improve the applicability to the complex piping network such as the secondary cooling water system in PWR's, we devised the equipotential control method that can eliminate undesired leakage currents outside a measurement section. In this paper, we present Wide Range Monitoring (WiRM) and Narrow Range Monitoring (NaRM) with Equipotential Switching Direct Current Potential Drop (ES-DCPD) method to rapidly monitor the thinning of piping. Based on the WiRM results, susceptible locations can be identified for further inspection by ultrasound technique (UT). On-line monitoring of a thinned location can be made by NaRM. Finite element analysis results and a closed-form resistance model are developed for the comparison with measured wall thinning by the developed DCPD technique. Verification experiments were conducted using UT as the reference. The result shows that model predictions and the experimental results agree well to confirm that both WiRM and NaRM based on ES-DCPD can be applicable to FAC management efforts

  10. Screening method for piping wall loss by flow accelerated corrosion

    International Nuclear Information System (INIS)

    Ryu, K.H.; Hwang, I.S.; Lee, N.Y.; Oh, Y.J.; Park, J.H.; Sohn, C.H.

    2007-01-01

    Flow accelerated corrosion (FAC) phenomenon has persisted in its impact on plant reliability and personnel safety. Unless we change the operation condition drastically, most parameters affecting FAC will not be effectively controlled. In order to help expand piping inspection coverage, we have developed a screening approach to monitor the wall thinning by a Direct Current Potential drop (DCPD) technique. To improve the applicability to the complex piping network such as the secondary cooling water system in PWR's, we devised the equipotential control method that can eliminate undesired leakage currents outside a measurement section. In this paper, we present Wide Range Monitoring (WiRM) and Narrow Range Monitoring (NaRM) with Equipotential Switching Direct Current Potential Drop (ES-DCPD) method to rapidly monitor the thinning of piping. Based on the WiRM results, susceptible locations can be identified for further inspection by Ultrasonic Technique (UT). On-line monitoring of a thinned location can be made by NaRM. Finite element analysis results and a closed-form resistance model are developed for the comparison with measured wall thinning by the developed DCPD technique. Verification experiments were conducted using UT as the reference. The result shows that model predictions and the experimental results agree well to confirm that both WiRM and NaRM based on ES-DCPD can be applicable to FAC management efforts. (author)

  11. Diamagnetic composite material structure for reducing undesired electromagnetic interference and eddy currents in dielectric wall accelerators and other devices

    Science.gov (United States)

    Caporaso, George J.; Poole, Brian R.; Hawkins, Steven A.

    2015-06-30

    The devices, systems and techniques disclosed here can be used to reduce undesired effects by magnetic field induced eddy currents based on a diamagnetic composite material structure including diamagnetic composite sheets that are separated from one another to provide a high impedance composite material structure. In some implementations, each diamagnetic composite sheet includes patterned conductor layers are separated by a dielectric material and each patterned conductor layer includes voids and conductor areas. The voids in the patterned conductor layers of each diamagnetic composite sheet are arranged to be displaced in position from one patterned conductor layer to an adjacent patterned conductor layer while conductor areas of the patterned conductor layers collectively form a contiguous conductor structure in each diamagnetic composite sheet to prevent penetration by a magnetic field.

  12. Partial discharges and bulk dielectric field enhancement

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Johansson, Torben

    2000-01-01

    A consequence of partial discharge activity within a gaseous void is the production of a field enhancement in the solid dielectric in the proximity of the void. This situation arises due to the charge created by the partial discharges accumulating at the void wall. The influence of the spatial...

  13. Moderate temperature-dependent surface and volume resistivity and low-frequency dielectric constant measurements of pure and multi-walled carbon nanotube (MWCNT) doped polyvinyl alcohol thin films

    Science.gov (United States)

    Edwards, Matthew; Guggilla, Padmaja; Reedy, Angela; Ijaz, Quratulann; Janen, Afef; Uba, Samuel; Curley, Michael

    2017-08-01

    Previously, we have reported measurements of temperature-dependent surface resistivity of pure and multi-walled carbon nanotube (MWNCT) doped amorphous Polyvinyl Alcohol (PVA) thin films. In the temperature range from 22 °C to 40 °C with humidity-controlled environment, we found the surface resistivity to decrease initially, but to rise steadily as the temperature continued to increase. Moreover, electric surface current density (Js) was measured on the surface of pure and MWCNT doped PVA thin films. In this regard, the surface current density and electric field relationship follow Ohm's law at low electric fields. Unlike Ohmic conduction in metals where free electrons exist, selected captive electrons are freed or provided from impurities and dopants to become conduction electrons from increased thermal vibration of constituent atoms in amorphous thin films. Additionally, a mechanism exists that seemingly decreases the surface resistivity at higher temperatures, suggesting a blocking effect for conducting electrons. Volume resistivity measurements also follow Ohm's law at low voltages (low electric fields), and they continue to decrease as temperatures increase in this temperature range, differing from surface resistivity behavior. Moreover, we report measurements of dielectric constant and dielectric loss as a function of temperature and frequency. Both the dielectric constant and dielectric loss were observed to be highest for MWCNT doped PVA compared to pure PVA and commercial paper, and with frequency and temperature for all samples.

  14. Influence of temperature on the dielectric nonlinearity of BaTiO{sub 3}-based multi-layer ceramic capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Seok-Hyun, E-mail: seokhyun72.yoon@samsung.com; Kim, Mi-Yang [LCR Materials Group, Corporate R& D Institute, Samsung Electro-Mechanics Co., Ltd., Suwon, Gyunggi-Do 443-743 (Korea, Republic of)

    2016-06-13

    Temperature dependence of the dielectric nonlinearity was investigated for the BaTiO{sub 3} multilayer ceramic capacitor. The decrease in temperature caused a significant increase in the degree of dielectric nonlinearity. The Preisach analysis shows that such effect corresponds to a decrease in reversible and a significant increase in irreversible domain wall contribution to polarization. The magnitude of spontaneous polarization (P{sub S}) was increased with decreasing temperature. It can be associated with phase transition from pseudo-cubic to monoclinic and its resultant change in the polar direction, which was observed through transmission electron microscopy. These results demonstrate that the increase in P{sub S} with the decrease in temperature inhibits domain wall motion in low driving field as it is anticipated to increase the degree of intergranular constraints during domain wall motion. But it results in a more steep increase in the dielectric constants beyond the threshold field where domain wall motion can occur.

  15. Online monitoring method using Equipotential Switching Direct Current potential drop for piping wall loss by flow accelerated corrosion

    International Nuclear Information System (INIS)

    Ryu, Kyung Ha; Lee, Tae Hyun; Kim, Ji Hak; Hwang, Il Soon; Lee, Na Young; Kim, Ji Hyun; Park, Jin Ho; Sohn, Chang Ho

    2010-01-01

    The flow accelerated corrosion (FAC) phenomenon persistently impacts plant reliability and personnel safety. We have shown that Equipotential Switching Direct Current Potential Drop (ES-DCPD) can be employed to detect piping wall loss induced by FAC. It has been demonstrated to have sufficient sensitivity to cover both long and short lengths of piping. Based on this, new FAC screening and inspection approaches have been developed. For example, resolution of ES-DCPD can be adjusted according to its monitoring purpose. The developed method shows good integrity during long test periods. It also shows good reproducibility. The Seoul National University FAC Accelerated Simulation Loop (SFASL) has been constructed for ES-DCPD demonstration purposes. During one demonstration, the piping wall was thinned by 23.7% through FAC for a 13,000 min test period. In addition to the ES-DCPD method, ultrasonic technique (UT) has been applied to SFASL for verification while water chemistry was continually monitored and controlled using electrochemical sensors. Developed electrochemical sensors showed accurate and stable water conditions in the SFASL during the test period. The ES-DCPD results were also theoretically predicted by the Sanchez-Caldera's model. The UT, however, failed to detect thinning because of its localized characteristics. Online UT that covers only local areas cannot assure the detection of wall loss.

  16. Rippled plasma wall accelerating structures

    International Nuclear Information System (INIS)

    Cavenago, M.

    1992-01-01

    A concept to form a hot, pulsed, inhomogeneous plasma and to use it as a linac structure is presented. The plasma spatial distribution is controlled by an external magnetic field and by the location of thermionic emitters; microwave ECR heating at frequency ω 1 favours plasma build up and reduces plasma resistivity. A shorter microwave pulse with frequency ω 2 ≠ ω 1 excites a longitudinal mode. An expression for the maximum attainable accelerating field is found. A linearized theory of accelerating modes is given. (Author) 6 refs., 3 figs

  17. An Examination of Resonance, Acceleration, and Particle Dynamics in the Micro-Accelerator Platform

    International Nuclear Information System (INIS)

    McNeur, Josh; Rosenzweig, J. B.; Travish, G.; Zhou, J.; Yoder, R.

    2010-01-01

    An effort to build a micron-scale dielectric-based slab-symmetric accelerator is underway at UCLA. The structure achieves acceleration via a resonant accelerating mode that is excited in an approximately 800 nm wide vacuum gap by a side coupled 800 nm laser. Detailed simulation results on structure fields and particle dynamics, using HFSS and VORPAL, are presented. We examine the quality factors of the accelerating modes for various structures and the excitations of non-accelerating destructive modes. Additionally, the results of an analytic and computational study of focusing, longitudinal dynamics and acceleration are described. Methods for achieving simultaneous transverse and longitudinal focusing are discussed, including modification of structure dimensions and slow variation of the coupling periodicity.

  18. Dielectric properties of carbon nanotubes/epoxy composites.

    Science.gov (United States)

    Peng, Jin-Ping; Zhang, Hui; Tang, Long-Cheng; Jia, Yu; Zhang, Zhong

    2013-02-01

    Material with high dielectric properties possesses the effect of energy storage and electric field homogenization, which plays an important role in the electrical and electronics domain, especially in the capacitor, electrical machinery and cable realm. In this paper, epoxy-based nanocomposites with high dielectric constant were fabricated by adding pristine and ozone functionalized multi-wall carbon nanotubes (MWCNTs). In the process-related aspect, the favorable technological parameter was obtained via reasonable arrangement and consideration of the dispersing methods including high-speed stirring and three-roller mill. As a result, a uniform dispersion status of MWCNTs in matrix has been guaranteed, which was observed by scanning and transmission electron microscopy. Meanwhile, the influence of different MWCNTs contents and diverse frequencies on the dielectric properties was compared. It was found that the dielectric constant of nano-composites decreased gradually with the increasing of frequency (10(3)-10(6) Hz). Moreover, as the content of MWCNTs increasing, the dielectric constant reached to a maximum of about 1,328 at 10(3) Hz when the pristine MWCNTs content was 0.5 wt.%. Accordingly, the DC conductivity results could interpret the peak value phenomenon by percolation threshold of MWCNTs. In addition, at the fixed content, the dielectric constant of epoxy-based nano-composites with ozone functionalized MWCNTs was lower than that of pristine ones.

  19. Compact particle accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Elizondo-Decanini, Juan M.

    2017-08-29

    A compact particle accelerator having an input portion configured to receive power to produce particles for acceleration, where the input portion includes a switch, is provided. In a general embodiment, a vacuum tube receives particles produced from the input portion at a first end, and a plurality of wafer stacks are positioned serially along the vacuum tube. Each of the plurality of wafer stacks include a dielectric and metal-oxide pair, wherein each of the plurality of wafer stacks further accelerate the particles in the vacuum tube. A beam shaper coupled to a second end of the vacuum tube shapes the particles accelerated by the plurality of wafer stacks into a beam and an output portion outputs the beam.

  20. Accelerated whole brain intracranial vessel wall imaging using black blood fast spin echo with compressed sensing (CS-SPACE).

    Science.gov (United States)

    Zhu, Chengcheng; Tian, Bing; Chen, Luguang; Eisenmenger, Laura; Raithel, Esther; Forman, Christoph; Ahn, Sinyeob; Laub, Gerhard; Liu, Qi; Lu, Jianping; Liu, Jing; Hess, Christopher; Saloner, David

    2018-06-01

    Develop and optimize an accelerated, high-resolution (0.5 mm isotropic) 3D black blood MRI technique to reduce scan time for whole-brain intracranial vessel wall imaging. A 3D accelerated T 1 -weighted fast-spin-echo prototype sequence using compressed sensing (CS-SPACE) was developed at 3T. Both the acquisition [echo train length (ETL), under-sampling factor] and reconstruction parameters (regularization parameter, number of iterations) were first optimized in 5 healthy volunteers. Ten patients with a variety of intracranial vascular disease presentations (aneurysm, atherosclerosis, dissection, vasculitis) were imaged with SPACE and optimized CS-SPACE, pre and post Gd contrast. Lumen/wall area, wall-to-lumen contrast ratio (CR), enhancement ratio (ER), sharpness, and qualitative scores (1-4) by two radiologists were recorded. The optimized CS-SPACE protocol has ETL 60, 20% k-space under-sampling, 0.002 regularization factor with 20 iterations. In patient studies, CS-SPACE and conventional SPACE had comparable image scores both pre- (3.35 ± 0.85 vs. 3.54 ± 0.65, p = 0.13) and post-contrast (3.72 ± 0.58 vs. 3.53 ± 0.57, p = 0.15), but the CS-SPACE acquisition was 37% faster (6:48 vs. 10:50). CS-SPACE agreed with SPACE for lumen/wall area, ER measurements and sharpness, but marginally reduced the CR. In the evaluation of intracranial vascular disease, CS-SPACE provides a substantial reduction in scan time compared to conventional T 1 -weighted SPACE while maintaining good image quality.

  1. A Phase Matching, Adiabatic Accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Lemery, Francois [Hamburg U.; Flöttmann, Klaus [DESY; Kärtner, Franz [CFEL, Hamburg; Piot, Philippe [Northern Illinois U.

    2017-05-01

    Tabletop accelerators are a thing of the future. Reducing their size will require scaling down electromagnetic wavelengths; however, without correspondingly high field gradients, particles will be more susceptible to phase-slippage – especially at low energy. We investigate how an adiabatically-tapered dielectric-lined waveguide could maintain phase-matching between the accelerating mode and electron bunch. We benchmark our simple model with CST and implement it into ASTRA; finally we provide a first glimpse into the beam dynamics in a phase-matching accelerator.

  2. High brightness electron accelerator

    International Nuclear Information System (INIS)

    Sheffield, R.L.; Carlsten, B.E.; Young, L.M.

    1994-01-01

    A compact high brightness linear accelerator is provided for use, e.g., in a free electron laser. The accelerator has a first plurality of accelerating cavities having end walls with four coupling slots for accelerating electrons to high velocities in the absence of quadrupole fields. A second plurality of cavities receives the high velocity electrons for further acceleration, where each of the second cavities has end walls with two coupling slots for acceleration in the absence of dipole fields. The accelerator also includes a first cavity with an extended length to provide for phase matching the electron beam along the accelerating cavities. A solenoid is provided about the photocathode that emits the electrons, where the solenoid is configured to provide a substantially uniform magnetic field over the photocathode surface to minimize emittance of the electrons as the electrons enter the first cavity. 5 figs

  3. Study of Corona Discharge on 160 KeV, 10 mA Electron Accelerator Facility Using FEM

    International Nuclear Information System (INIS)

    Ghazali, Abu Bakar Mhd; Sobri, Rokiah Mohd

    2008-01-01

    This paper describes a method to verify the overall design of our electron accelerator. It is free from corona or spark discharge phenomenon. This locally designed electron accelerator facility is located at Nuclear Malaysia Complex, Bangi, Selangor. In this study, we describe the geometry of the pressure vessel filled with SF 6 gas at 2 atm to enclose the high voltage area of the accelerating tube. The Poisson's equation is used to calculate the contours of the electric field that is created between the cathode of -160 kV maximum and the wall of the vessel. The nearest sharp edge between the cathode and the pressure wall is 163 mm apart. The calculation is based on finite element method (FEM) for electrostatic charges in order to obtain an electric field contour in two-dimensional plane. We found that the surface charge density of the cathode is 1.1x10 -5 C/m 2 for the corona glowing seen at -90 kV. Moreover, the highest electric field near to (about 5 mm from) the sharp edge is about 2.7 MV/m, which is less than the dielectric strength of SF 6 gas, i.e. 6 MV/m and therefore, it proved that our design of the pressure vessel is save from corona or spark discharges

  4. Study of Corona Discharge on 160 KeV, 10 mA Electron Accelerator Facility Using FEM

    Science.gov (United States)

    Ghazali, Abu Bakar Mhd; Sobri, Rokiah Mohd

    2008-05-01

    This paper describes a method to verify the overall design of our electron accelerator. It is free from corona or spark discharge phenomenon. This locally designed electron accelerator facility is located at Nuclear Malaysia Complex, Bangi, Selangor. In this study, we describe the geometry of the pressure vessel filled with SF6 gas at 2 atm to enclose the high voltage area of the accelerating tube. The Poisson's equation is used to calculate the contours of the electric field that is created between the cathode of -160 kV maximum and the wall of the vessel. The nearest sharp edge between the cathode and the pressure wall is 163 mm apart. The calculation is based on finite element method (FEM) for electrostatic charges in order to obtain an electric field contour in two-dimensional plane. We found that the surface charge density of the cathode is 1.1×10-5 C/m2 for the corona glowing seen at -90 kV. Moreover, the highest electric field near to (about 5 mm from) the sharp edge is about 2.7 MV/m, which is less than the dielectric strength of SF6 gas, i.e. 6 MV/m and therefore, it proved that our design of the pressure vessel is save from corona or spark discharges.

  5. Photonic Crystal Laser-Driven Accelerator Structures

    International Nuclear Information System (INIS)

    Cowan, Benjamin M.

    2007-01-01

    Laser-driven acceleration holds great promise for significantly improving accelerating gradient. However, scaling the conventional process of structure-based acceleration in vacuum down to optical wavelengths requires a substantially different kind of structure. We require an optical waveguide that (1) is constructed out of dielectric materials, (2) has transverse size on the order of a wavelength, and (3) supports a mode with speed-of-light phase velocity in vacuum. Photonic crystals---structures whose electromagnetic properties are spatially periodic---can meet these requirements. We discuss simulated photonic crystal accelerator structures and describe their properties. We begin with a class of two-dimensional structures which serves to illustrate the design considerations and trade-offs involved. We then present a three-dimensional structure, and describe its performance in terms of accelerating gradient and efficiency. We discuss particle beam dynamics in this structure, demonstrating a method for keeping a beam confined to the waveguide. We also discuss material and fabrication considerations. Since accelerating gradient is limited by optical damage to the structure, the damage threshold of the dielectric is a critical parameter. We experimentally measure the damage threshold of silicon for picosecond pulses in the infrared, and determine that our structure is capable of sustaining an accelerating gradient of 300 MV/m at 1550 nm. Finally, we discuss possibilities for manufacturing these structures using common microfabrication techniques

  6. Multi-stage wake-field accelerator

    International Nuclear Information System (INIS)

    Gai, Wei.

    1989-01-01

    In this paper we propose a multi-stage wake field acceleration scheme to overcome the low transformer ratio problem and still provide high accelerating gradients. The idea is very simple. We use a train of several electron bunches from a linear accelerator (main linac) with well defined separations between the bunches (tens of ns) to drive wake field devices. Here we have made the assumption that the wake field devices are available, whether plasma, iris-loaded metallic or dielectric wake field structures. 10 refs

  7. Linear particle accelerator

    International Nuclear Information System (INIS)

    Richards, J.A.

    1977-01-01

    A linear particle accelerator which provides a pulsed beam of charged particles of uniform energy is described. The accelerator is in the form of an evacuated dielectric tube, inside of which a particle source is located at one end of the tube, with a target or window located at the other end of the dielectric tube. Along the length of the tube are externally located pairs of metal plates, each insulated from each other in an insulated housing. Each of the plates of a pair are connected to an electrical source of voltage of opposed polarity, with the polarity of the voltage of the plates oriented so that the plate of a pair, nearer to the particle source, is of the opposed polarity to the charge of the particle emitted by the source. Thus, a first plate about the tube located nearest the particle source, attracts a particle which as it passes through the tube past the first plate is then repelled by the reverse polarity of the second plate of the pair to continue moving towards the target

  8. Testing quantised inertia on emdrives with dielectrics

    Science.gov (United States)

    McCulloch, M. E.

    2017-05-01

    Truncated-cone-shaped cavities with microwaves resonating within them (emdrives) move slightly towards their narrow ends, in contradiction to standard physics. This effect has been predicted by a model called quantised inertia (MiHsC) which assumes that the inertia of the microwaves is caused by Unruh radiation, more of which is allowed at the wide end. Therefore, photons going towards the wide end gain inertia, and to conserve momentum the cavity must move towards its narrow end, as observed. A previous analysis with quantised inertia predicted a controversial photon acceleration, which is shown here to be unnecessary. The previous analysis also mispredicted the thrust in those emdrives with dielectrics. It is shown here that having a dielectric at one end of the cavity is equivalent to widening the cavity at that end, and when dielectrics are considered, then quantised inertia predicts these results as well as the others, except for Shawyer's first test where the thrust is predicted to be the right size but in the wrong direction. As a further test, quantised inertia predicts that an emdrive's thrust can be enhanced by using a dielectric at the wide end.

  9. The Effect of Multi Wall Carbon Nanotubes on Some Physical Properties of Epoxy Matrix

    Science.gov (United States)

    Al-Saadi, Tagreed M.; hammed Aleabi, Suad; Al-Obodi, Entisar E.; Abdul-Jabbar Abbas, Hadeel

    2018-05-01

    This research involves using epoxy resin as a matrix for making a composite material, while the multi wall carbon nanotubes (MWNCTs) is used as a reinforcing material with different fractions (0.0,0.02, 0.04, 0.06) of the matrix weight. The mechanical ( hardness ), electrical ( dielectric constant, dielectric loss factor, dielectric strength, electrical conductivity ), and thermal properties (thermal conductivity ) were studied. The results showed the increase of hardness, thermal conductivity, electrical conductivity and break down strength with the increase of MWCNT concentration, but the behavior of dielectric loss factor and dielectric constant is opposite that.

  10. Driver-witness electron beam acceleration in dielectric mm-scale capillaries

    Science.gov (United States)

    Lekomtsev, K.; Aryshev, A.; Tishchenko, A. A.; Shevelev, M.; Lyapin, A.; Boogert, S.; Karataev, P.; Terunuma, N.; Urakawa, J.

    2018-05-01

    We investigated a corrugated mm-scale capillary as a compact accelerating structure in the driver-witness acceleration scheme, and suggested a methodology to measure the acceleration of the witness bunch. The accelerating fields produced by the driver bunch and the energy spread of the witness bunch in a corrugated capillary and in a capillary with a constant inner radius were measured and simulated for both on-axis and off-axis beam propagation. Our simulations predicted a change in the accelerating field structure for the corrugated capillary. Also, an approximately twofold increase of the witness bunch energy gain on the first accelerating cycle was expected for both capillaries for the off-axis beam propagation. These results were confirmed in the experiment, and the maximum measured acceleration of 170 keV /m at 20 pC driver beam charge was achieved for off-axis beam propagation. The driver bunch showed an increase in energy spread of up to 11%, depending on the capillary geometry and beam propagation, with a suppression of the longitudinal energy spread in the witness bunch of up to 15%.

  11. Fluid-structure-interaction analysis for welded pipes with flow-accelerated corrosion wall thinning

    Energy Technology Data Exchange (ETDEWEB)

    Sun, L.; Ding, Y., E-mail: lan.sun@cnl.ca [Canadian Nuclear Laboratories, Chalk River, Ontario (Canada)

    2016-06-15

    The flow-accelerated corrosion (FAC) entrance effect results in enhanced wall thinning immediately downstream of a weld if the weld connects an upstream FAC-resistant material with a downstream less resistant material. The weld regions, especially those with local repairs, are susceptible to cracking due to the high residual stresses induced by fabrication. The combined effects of the FAC entrance effect and high stresses at a weld might compromise the structural integrity of the piping and lead to a failure. Weld degradation by FAC entrance effect has been observed at nuclear and fossil power plants. This paper describes an application using fluid-structure-interaction (FSI) modelling to study the combined effects of FAC wall thinning, weld residual stresses, and in-service loads on welded structures. Simplified cases analyzed were based on CANDU outlet feeder conditions. The analysis includes the flow and mass transfer modelling of the FAC entrance effect using computational fluid dynamics (CFD) and nonlinear structural analyses of the welded structures with wall thinning and an assumed weld residual stress and strain distribution. The FSI analyses were performed using ANSYS Workbench, an integrated platform that enables the coupling of CFD and structural analysis solutions. The obtained results show that the combination of FAC, weld residual stresses, in-service loads (including the internal pressure) and (or) extreme loads could cause high stresses and affect the integrity of the welded pipes. The present work demonstrated that the FSI modelling can be used as an effective approach to assess the integrity of welded structures. (author)

  12. Advanced Accelerators for Medical Applications

    Science.gov (United States)

    Uesaka, Mitsuru; Koyama, Kazuyoshi

    We review advanced accelerators for medical applications with respect to the following key technologies: (i) higher RF electron linear accelerator (hereafter “linac”); (ii) optimization of alignment for the proton linac, cyclotron and synchrotron; (iii) superconducting magnet; (iv) laser technology. Advanced accelerators for medical applications are categorized into two groups. The first group consists of compact medical linacs with high RF, cyclotrons and synchrotrons downsized by optimization of alignment and superconducting magnets. The second group comprises laser-based acceleration systems aimed of medical applications in the future. Laser plasma electron/ion accelerating systems for cancer therapy and laser dielectric accelerating systems for radiation biology are mentioned. Since the second group has important potential for a compact system, the current status of the established energy and intensity and of the required stability are given.

  13. Flame acceleration due to wall friction: Accuracy and intrinsic limitations of the formulations

    Science.gov (United States)

    Demirgok, Berk; Sezer, Hayri; Akkerman, V.'Yacheslav

    2015-11-01

    The analytical formulations on the premixed flame acceleration induced by wall friction in two-dimensional (2D) channels [Bychkov et al., Phys. Rev. E 72 (2005) 046307] and cylindrical tubes [Akkerman et al., Combust. Flame 145 (2006) 206] are revisited. Specifically, pipes with one end closed are considered, with a flame front propagating from the closed pipe end to the open one. The original studies provide the analytical formulas for the basic flame and fluid characteristics such as the flame acceleration rate, the flame shape and its propagation speed, as well as the flame-generated flow velocity profile. In the present work, the accuracy of these approaches is verified, computationally, and the intrinsic limitations and validity domains of the formulations are identified. Specifically, the error diagrams are presented to demonstrate how the accuracy of the formulations depends on the thermal expansion in the combustion process and the Reynolds number associated with the flame propagation. It is shown that the 2D theory is accurate enough for a wide range of parameters. In contrast, the zeroth-order approximation for the cylindrical configuration appeared to be quite inaccurate and had to be revisited. It is subsequently demonstrated that the first-order approximation for the cylindrical geometry is very accurate for realistically large thermal expansions and Reynolds numbers. Consequently, unlike the zeroth-order approach, the first-order formulation can constitute a backbone for the comprehensive theory of the flame acceleration and detonation initiation in cylindrical tubes. Cumulatively, the accuracy of the formulations deteriorates with the reduction of the Reynolds number and thermal expansion.

  14. Two-dimensional photonic crystal accelerator structures

    Directory of Open Access Journals (Sweden)

    Benjamin M. Cowan

    2003-10-01

    Full Text Available Photonic crystals provide a method of confining a synchronous speed-of-light mode in an all-dielectric structure, likely a necessary feature in any optical accelerator. We explore computationally a class of photonic crystal structures with translational symmetry in a direction transverse to the electron beam. We demonstrate synchronous waveguide modes and discuss relevant parameters of such modes. We then explore how accelerator parameters vary as the geometry of the structure is changed and consider trade-offs inherent in the design of an accelerator of this type.

  15. Mass transfer effects in feeder flow-accelerated corrosion wall thinning

    International Nuclear Information System (INIS)

    Pietralik, J.

    2008-01-01

    Flow conditions play a dominant role in Flow-Accelerated Corrosion (FAC) under certain conditions, e.g., in CANDU feeders. While chemistry and materials set the overall potential for FAC, flow conditions determine the local distribution of wall thinning. Recent plant data of feeders and laboratory tests confirms that there is a close relationship between local flow conditions, expressed by mass transfer coefficient, and FAC rate in CANDU feeder bends. The knowledge of local effects can be useful for minimizing the number of inspected components, predicting the location of the highest FAC rate for a given piping component, and determining what components or feeders should be replaced. A similar evaluation applies also to FAC in heat transfer equipment such as heat exchangers and steam generators. The objective of this paper is to examine the relationship between FAC rate and local mass transfer parameters. For FAC where the flow is dominant, the FAC rate is proportional to mass flux of ferrous ions. The mass flux is the product of the mass transfer coefficient and the concentration difference, or degree of saturation. The mass transfer coefficient describes the intensity of the transport of corrosion products (ferrous ions) from the oxide-water interface into the bulk water. Therefore, this parameter can be used for predicting the local distribution of FAC rate in the mass-transfer controlled FAC. The degree of saturation reduces the mass flux, thus reducing the FAC rate. This effect can be significant in long piping, e.g., in outlet feeders. The paper presents plant and laboratory evidence for the relationship between local mass transfer conditions and the FAC rate. It shows correlations for mass transfer coefficient in components that are highly susceptible to FAC and most important flow parameters that affect mass transfer coefficient. The role of surface roughness, wall shear stress, and local turbulence is also discussed. (author)

  16. The Impact of Dielectric Material and Temperature on Dielectric Charging in RF MEMS Capacitive Switches

    Science.gov (United States)

    Papaioannou, George

    The present work attempts to provide a better insight on the dielectric charging in RF-MEMS capacitive switches that constitutes a key issue limiting parameter of their commercialization. The dependence of the charging process on the nature of dielectric materials widely used in these devices, such as SiO2, Si3N4, AlN, Al2O3, Ta2O5, HfO2, which consist of covalent or ionic bonds and may exhibit piezoelectric properties is discussed taking into account the effect of deposition conditions and resulting material stoichiometry. Another key issue parameter that accelerates the charging and discharging processes by providing enough energy to trapped charges to be released and to dipoles to overcome potential barriers and randomize their orientation is the temperature will be investigated too. Finally, the effect of device structure will be also taken into account.

  17. The transverse forces in wakefield accelerators

    International Nuclear Information System (INIS)

    Rosing, M.; Gai, W.

    1990-01-01

    An attempt is presented to compare beam breakup problems in dielectric lined waveguide with plasmas as they pertain to wakefield accelerators. In the waveguide position it is measured relative to the physical center of the guide but in a plasma position it is relative to the centroid of the bunch creating the wakes. Dielectrics are very linear making their behaviour well suited for analytical study. Plasmas are very nonlinear so many approximations should be made to put them into an analytical regime. (R.P.) 6 refs.; 4 figs

  18. Application of flexi-wall in noise barriers renewal

    Directory of Open Access Journals (Sweden)

    B. Daee

    2015-12-01

    Full Text Available This paper presents an experimental study on structural performance of an innovative noise barrier consisting of poly-block, light polyurethane foam (LPF and polyurea. This wall system (flexi-wall is intended to be employed as a vertical extension to existing noise barriers (sound walls in an accelerated construction method. To aid in the wall design, several mechanical tests were conducted on LPF specimens and two full-scale walls were then fabricated employing the same LPF material. The full-scale walls were subjected to lateral loading in order to establish their lateral resistance. A cyclic fatigue test was also performed on a full-scale flexi-wall in order to evaluate the performance of the wall under a repetitive loading condition. The results of the experiments indicated the suitability of flexi-wall in accelerated construction and confirmed that the structural performance of the wall system under lateral loading is satisfactory for the sound wall application. The experimental results were discussed and a preliminary design procedure for application of flexi-wall in sound wall applications was also developed.

  19. Spectroscopic observations of an arc-plasma accelerator

    International Nuclear Information System (INIS)

    Clothiaux, E.J.

    1990-01-01

    Spectra from in-bore and from the muzzle flash of an arc-plasma accelerator have been observed, and a strong absorption in the uv is observed in-bore. High pressure at the wall of the arc-plasma accelerator, >800 Bar, suggests a high on-axis equilibrium temperature and a high opacity. Time-resolved measurements of the in-bore emission, at four spectral points, give a peak temperature at the accelerator wall of ≅200,000 o K. (author)

  20. Photonic laser-driven accelerator for GALAXIE

    Energy Technology Data Exchange (ETDEWEB)

    Naranjo, B.; Ho, M.; Hoang, P.; Putterman, S.; Valloni, A.; Rosenzweig, J. B. [UCLA Dept. of Physics and Astronomy Los Angeles, CA 90095-1547 (United States)

    2012-12-21

    We report on the design and development of an all-dielectric laser-driven accelerator to be used in the GALAXIE (GV-per-meter Acce Lerator And X-ray-source Integrated Experiment) project's compact free-electron laser. The approach of our working design is to construct eigenmodes, borrowing from the field of photonics, which yield the appropriate, highly demanding dynamics in a high-field, short wavelength accelerator. Topics discussed include transverse focusing, power coupling, bunching, and fabrication.

  1. An Inverse Free-Electron-Laser accelerator

    International Nuclear Information System (INIS)

    Fisher, A.S.; Gallardo, J.C.; van Steenbergen, A.; Ulc, S.; Woodle, M.; Sandweiss, J.; Fang, Jyan-Min

    1993-01-01

    Recent work at BNL on electron acceleration using the Inverse Free-Electron Laser (IFEL) has considered a low-energy, high-gradient, multi-stage linear accelerator. Experiments are planned at BNL's Accelerator Test Facility using its 50-MeV linac and 100-GW CO 2 laser. We have built and tested a fast-excitation wiggler magnet with constant field, tapered period, and overall length of 47 cm. Vanadium-Permendur ferromagnetic laminations are stacked in alternation with copper, eddy-current-induced, field reflectors to achieve a 1.4-T peak field with a 4-mm gap and a typical period of 3 cm. The laser beam will pass through the wiggler in a low-loss, dielectric-coated stainless-steel, rectangular waveguide. The attenuation and transverse mode has been measured in waveguide sections of various lengths, with and without the dielectric. Results of 1-D and 3-D IFEL simulations, including wiggler errors, will be presented for several cases: the initial, single-module experiment with ΔE = 39 MeV, a four-module design giving ΔE = 100 MeV in a total length of 2 m, and an eight-module IFEL with ΔE = 210 MeV

  2. Confinement in single walled carbon nanotubes investigated by spectroscopic ellipsometry

    International Nuclear Information System (INIS)

    Battie, Y.; Jamon, D.; Lauret, J.S.; Gu, Q.; Gicquel-Guézo, M.; En Naciri, A.; Loiseau, A.

    2014-01-01

    Thick films of single walled carbon nanotubes (SWCNTs) with different diameter and chirality distributions are characterized by combining transmission electron microscopy and spectroscopic ellipsometry. The dependence of the dielectric function with the increase of the SWCNT diameter occurs with a drastic redshift of the S 11 , S 22 and M 11 transition energies. The transfer integral parameter γ 0 of SWCNT is also evaluated and analyzed. We demonstrate that parts of the optical properties of SWCNTs are attributed to a one dimensional confinement effect. - Highlights: • Ellipsometric measurements are performed on carbon nanotube thick films. • The complex dielectric functions of conventional carbon nanotubes are given. • Confinement effects explain the variations of dielectric function of nanotubes

  3. A dielectric method for measuring early and late reactions in irradiated human skin

    International Nuclear Information System (INIS)

    Nuutinen, J.; Lahtinen, T.; Turunen, M.; Alanen, E.; Tenhunen, M.; Usenius, T.; Kolle, R.

    1998-01-01

    Background and purpose: To measure the dielectric constant of irradiated human skin in order to test the feasibility of the dielectric measurements in the quantitation of acute and late radiation reactions. Materials and methods: The dielectric constant of irradiated breast skin was measured at an electromagnetic frequency of 300 MHz in 21 patients during postmastectomy radiotherapy. The measurements were performed with an open-ended coaxial line reflection method. The irradiation technique consisted of an anterior photon field to the lymph nodes and a matched electron field to the chest wall using conventional fractionation of five fractions/week to 50 Gy. Fourteen out of the 21 patients were remeasured 2 years later and the skin was palpated for subcutaneous fibrosis. Results: At 5 weeks the dielectric constant had decreased by 31 and 39% for the investigated skin sites of the photon and electron fields, respectively. There was a statistically significant inverse correlation between the mean dielectric constant and the clinical score of erythema. An unexpected finding was a decrease of the dielectric constant of the contralateral healthy skin during radiotherapy. Two years later a statistically significant positive correlation was found between the dielectric constant at the irradiated skin sites and the clinical score of subcutaneous fibrosis. Conclusions: Dielectric measurements non-invasively yield quantitative information concerning radiation-induced skin reactions. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  4. Spectroscopic observations of an arc-plasma accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Clothiaux, E.J. (Auburn Univ., AL (USA). Dept. of Physics)

    Spectra from in-bore and from the muzzle flash of an arc-plasma accelerator have been observed, and a strong absorption in the uv is observed in-bore. High pressure at the wall of the arc-plasma accelerator, >800 Bar, suggests a high on-axis equilibrium temperature and a high opacity. Time-resolved measurements of the in-bore emission, at four spectral points, give a peak temperature at the accelerator wall of {approx equal}200,000{sup o}K. (author).

  5. Optimized extraction conditions from high power-ECRIS by dedicated dielectric structures

    International Nuclear Information System (INIS)

    Schachter, L.; Dobrescu, S.; Stiebing, K.E.

    2012-01-01

    The MD-method of enhancing the ion output from ECR ion sources is well established and basically works via two mechanisms, the regenerative injection of cold electrons from an emissive dielectric layer on the plasma chamber walls and via the cutting of compensating wall currents, which results in an improved ion extraction from the plasma. As this extraction from the plasma becomes a more and more challenging issue for modern ECRIS installations with high microwave power input, a series of experiments was carried out at the 14 GHz ECRIS of the Institut fuer Kernphysik in Frankfurt/Main, Germany (IKF). In contrast to our earlier work, in these experiments emphasis was put on the second of the above mechanisms namely to influence the sheath potential at the extraction by structures with special dielectric properties. Two different types of dielectric structures, Tantalum-oxide and Aluminium oxide (the latter also being used for the MD-method) with dramatically different electrical properties were mounted on the extraction electrode of the IKF-ECRIS, facing the plasma. For both structures an increase of the extracted ion beam currents for middle and high charge states by 60-80 % was observed. The method can also be applied to other ECR ion sources for increasing the extracted ion beam performances. The paper is followed by the slides of the presentation. (authors)

  6. Cockroft Walton accelerator prototype

    International Nuclear Information System (INIS)

    Hutapea, Sumihar.

    1976-01-01

    Prototype of a Cockroft Walton generator using ceramic and plastic capacitors is discussed. Compared to the previous generator, the construction and components are much more improved. Pralon is used for the high voltage insulation column and plastic is used as a dielectric material for the high voltage capacitor. Cockroft Walton generator is used as a high tension supply for an accelerator. (author)

  7. Ultrasound Instrumentation for Beam Diagnostics and Accelerating Structures Control

    CERN Document Server

    Moiseev, V I

    2005-01-01

    Sensitive elements and electronics for ultrasound measurements at conducting walls of beam pipes and accelerating structures are described. Noise protected instrumentation provides ultrasound spectra analysis in a wide frequency range up to 5 MHz.In circular accelerators, ultrasound fields in conducting walls of beam pipe represent the space-time characteristics of circulating beams. In accelerating structures, real high power operation modes of structure can be studied by outer ultrasound monitors. The experimental results at KSRS accelerators are discussed.

  8. Pulsed electron accelerator for radiation technologies in the enviromental applications

    Science.gov (United States)

    Korenev, Sergey

    1997-05-01

    The project of pulsed electron accelerator for radiation technologies in the environmental applications is considered. An accelerator consists of high voltage generator with vacuum insulation and vacuum diode with plasma cathode on the basis discharge on the surface of dielectric of large dimensions. The main parameters of electron accelerators are following: kinetic energy 0.2 - 2.0 MeV, electron beam current 1 - 30 kA and pulse duration 1- 5 microseconds. The main applications of accelerator for decomposition of wastewaters are considered.

  9. An Adiabatic Phase-Matching Accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Lemery, Francois [DESY; Floettmann, Klaus [DESY; Piot, Philippe [Northern Illinois U.; Kaertner, Franz X. [Hamburg U.; Assmann, Ralph [DESY

    2017-12-22

    We present a general concept to accelerate non-relativistic charged particles. Our concept employs an adiabatically-tapered dielectric-lined waveguide which supports accelerating phase velocities for synchronous acceleration. We propose an ansatz for the transient field equations, show it satisfies Maxwell's equations under an adiabatic approximation and find excellent agreement with a finite-difference time-domain computer simulation. The fields were implemented into the particle-tracking program {\\sc astra} and we present beam dynamics results for an accelerating field with a 1-mm-wavelength and peak electric field of 100~MV/m. The numerical simulations indicate that a $\\sim 200$-keV electron beam can be accelerated to an energy of $\\sim10$~MeV over $\\sim 10$~cm. The novel scheme is also found to form electron beams with parameters of interest to a wide range of applications including, e.g., future advanced accelerators, and ultra-fast electron diffraction.

  10. An electromagnetic model for post-wall waveguide building blocks

    NARCIS (Netherlands)

    Coenen, T.J.; Bekers, D.J.; Tauritz, J.L.; Vliet, van F.E.

    2010-01-01

    During the past five years, dielectric and metallic post-wall waveguides (PWWGs) have been analyzed at TNO Defence, Security and Safety, using both an integral equation approach and a modal approach. The model developed focuses on TEn0 modes facilitating the analysis of infinitelylong, straight

  11. Super dielectric capacitor using scaffold dielectric

    OpenAIRE

    Phillips, Jonathan

    2018-01-01

    Patent A capacitor having first and second electrodes and a scaffold dielectric. The scaffold dielectric comprises an insulating material with a plurality of longitudinal channels extending across the dielectric and filled with a liquid comprising cations and anions. The plurality of longitudinal channels are substantially parallel and the liquid within the longitudinal channels generally has an ionic strength of at least 0.1. Capacitance results from the migrations of...

  12. Plasma-focused cyclic accelerators

    International Nuclear Information System (INIS)

    Mondelli, A.A.; Chernin, D.P.

    1985-01-01

    The use of ambient plasma to neutralize the transverse forces of an intense particle beam has been known for many years. Most recently, the so-called ion-focused regime (IFR) for beam propagation has been used as a means of focusing intense electron beams in linear accelerators and suggested for injecting an electron beam across magnetic field lines into a high-current cyclic accelerator. One technique for generating the required background plasma for IFR propagation is to use a laser to ionize ambient gas in the accelerator chamber. For cyclic accelerators a technique is required for carrying the plasma channel and the beam around a bend. Multiple laser-generated channels with dipole magnetic fields to switch the beam from one channel to the next have been tested at Sandia. This paper discusses an alternative means of plasma production for IFR, viz. by using rf breakdown. For this approach the accelerator chamber acts as a waveguide. With a suitable driving frequency, a waveguide mode can be driven which has its peak field intensity on the axis with negligible fields at the chamber walls. The plasma production and hence the beam propagation is thereby isolated from the walls. This technique is not limited to toroidal accelerators. It may be applied to any accelerator or recirculator geometry as well as for beam steering and for injection or extraction of beams in closed accelerator configurations

  13. Method of making dielectric capacitors with increased dielectric breakdown strength

    Science.gov (United States)

    Ma, Beihai; Balachandran, Uthamalingam; Liu, Shanshan

    2017-05-09

    The invention is directed to a process for making a dielectric ceramic film capacitor and the ceramic dielectric laminated capacitor formed therefrom, the dielectric ceramic film capacitors having increased dielectric breakdown strength. The invention increases breakdown strength by embedding a conductive oxide layer between electrode layers within the dielectric layer of the capacitors. The conductive oxide layer redistributes and dissipates charge, thus mitigating charge concentration and micro fractures formed within the dielectric by electric fields.

  14. High energy particle acceleration by relativistic plasma waves

    International Nuclear Information System (INIS)

    Amiranoff, F.; Jacquet, F.; Mora, P.; Matthieussent, G.

    1991-01-01

    Accelerating schemes using plasmas, lasers or electron beams are proposed and compared to electron bunches in dielectric media or laser propagation through a slow wave structure made of liquid droplets. (L.C.J.A.). 33 refs, 20 figs

  15. Advanced Accelerator Test Facility (AATF) upgrade plan

    International Nuclear Information System (INIS)

    Gai, W.; Ho, C.; Konecny, R.

    1989-01-01

    We have successfully demonstrated the principles of wake-field acceleration using structures (cavity, dielectric) and plasmas as wake-field devices using the AATF at Argonne National Laboratory. Due to the limited driver electron pulse intensity and relative long pulse length, only modest accelerating gradients were observed. In order to study the wake field effects in much greater detail and demonstrate the feasibility of wake-field accelerator for high energy physics, we are considering construction of a laser photocathode injector on the existing 20 MeV Chem-Linac to produce very intense and short electron pulses. 10 refs., 5 figs

  16. Enhanced performance in capacitive force sensors using carbon nanotube/polydimethylsiloxane nanocomposites with high dielectric properties

    Science.gov (United States)

    Jang, Hyeyoung; Yoon, Hyungsuk; Ko, Youngpyo; Choi, Jaeyoo; Lee, Sang-Soo; Jeon, Insu; Kim, Jong-Ho; Kim, Heesuk

    2016-03-01

    Force sensors have attracted tremendous attention owing to their applications in various fields such as touch screens, robots, smart scales, and wearable devices. The force sensors reported so far have been mainly focused on high sensitivity based on delicate microstructured materials, resulting in low reproducibility and high fabrication cost that are limitations for wide applications. As an alternative, we demonstrate a novel capacitive-type force sensor with enhanced performance owing to the increased dielectric properties of elastomers and simple sensor structure. We rationally design dielectric elastomers based on alkylamine modified-multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) composites, which have a higher dielectric constant than pure PDMS. The alkylamine-MWCNTs show excellent dispersion in a PDMS matrix, thus leading to enhanced and reliable dielectric properties of the composites. A force sensor array fabricated with alkylamine-MWCNT/PDMS composites presents an enhanced response due to the higher dielectric constant of the composites than that of pure PDMS. This study is the first to report enhanced performance of capacitive force sensors by modulating the dielectric properties of elastomers. We believe that the disclosed strategy to improve the sensor performance by increasing the dielectric properties of elastomers has great potential in the development of capacitive force sensor arrays that respond to various input forces.Force sensors have attracted tremendous attention owing to their applications in various fields such as touch screens, robots, smart scales, and wearable devices. The force sensors reported so far have been mainly focused on high sensitivity based on delicate microstructured materials, resulting in low reproducibility and high fabrication cost that are limitations for wide applications. As an alternative, we demonstrate a novel capacitive-type force sensor with enhanced performance owing to the increased

  17. Dielectric and thermal properties of the methacrylate polymer bearing chalcone side group

    Science.gov (United States)

    Çelik, Taner; Coşkun, Mehmet Fatih

    2018-04-01

    The 1-(1-benzofuran-2yl)-3-(4-hydroxyphenyl)propen-1-one (compound 1) from the reaction between 1-(1-benzofuran-2-yl) ethanone and 4-hydroxybenzaldehyde was firstly synthesized. And secondly, we synthesized 4-[3-(1-benzofuran-2-yl)-3-oxoprop-1-en-1-yl] phenyl chloroacetate (compound 2) as the result of the reaction between the compound 1 and chloroacetyl chloride. The monomer was prepared by the reaction of compound 2 and sodium methacrylate. The monomer was polymerized using the free radicalic polymerization method (FRP). The structure characterization of the polymer was determined utilizing 1H,13C- NMR and FT-IR techniques. Thermal behaviour of the homopolymer was studied by measurements of TGA and DSC. For thermal decomposition kinetics of homopolymer, Flynn-Wall-Ozawa method was applied to thermogravimetry curves. The dielectric measurements were studied using the impedance analyzer technique at a frequency which varied between 100 Hz and 20 kHz Hz depending on the alternating current (AC) conductivities. The dielectric parameters such as dielectric constant and dielectric loss are changed with the temperature.

  18. The UCLA/SLAC Ultra-High Gradient Cerenkov Wakefield Accelerator Experiment

    CERN Document Server

    Thompson, Matthew C; Hogan, Mark; Ischebeck, Rasmus; Muggli, Patric; Rosenzweig, James E; Scott, A; Siemann, Robert; Travish, Gil; Walz, Dieter; Yoder, Rodney

    2005-01-01

    An experiment is planned to study the performance of dielectric Cerenkov wakefield accelerating structures at extremely high gradients in the GV/m range. This new UCLA/SLAC collaboration will take advantage of the unique SLAC FFTB electron beam and its demonstrated ultra-short pulse lengths and high currents (e.g., sz = 20 μm at Q = 3 nC). The electron beam will be focused down and sent through varying lengths of fused silica capillary tubing with two different sizes: ID = 200 μm / OD = 325 μm and ID = 100 μm / OD = 325 μm. The pulse length of the electron beam will be varied in order to alter the accelerating gradient and probe the breakdown threshold of the dielectric structures. In addition to breakdown studies, we plan to collect and measure coherent Cerenkov radiation emitted from the capillary tube to gain information about the strength of the accelerating fields. Status and progress on the experiment are reported.

  19. Accelerators in industrial and clinical practice

    International Nuclear Information System (INIS)

    Kulinich, S.

    1983-01-01

    Various possible accelerator applications in the USSR are given, namely the use of a linear electron accelerator in crack detection of thick-walled steel products, the use of accelerators in the radiation-chemical production of antimicrobial fabrics, the use of a pulsed electron accelerator for the disinfection of sewage waters, the use of accelerators for the treatment of tumors. Instruments have been developed on the basis of linear electron accelerators for the activation analysis of ores. (M.D.)

  20. Bubbles in the self-accelerating universe

    International Nuclear Information System (INIS)

    Izumi, Keisuke; Tanaka, Takahiro; Koyama, Kazuya; Pujolas, Oriol

    2007-01-01

    We revisit the issue of the stability in the Dvali-Gabadadze-Porrati model by considering the nucleation of bubbles of the conventional branch within the self-accelerating branch. We construct an instanton describing this process in the thin wall approximation. On one side of the bubble wall, the bulk consists of the exterior of the brane, while on the other side it is the interior. The solution requires the presence of a 2-brane (the bubble wall) which induces the transition. However, we show that this instanton cannot be realized as the thin wall limit of any smooth solution. Once the bubble thickness is resolved, the equations of motion do not allow O(4) symmetric solutions joining the two branches. We conclude that the thin wall instanton is unphysical, and that one cannot have processes connecting the two branches, unless negative tension bubble walls are introduced. This also suggests that the self-accelerating branch does not decay into the conventional branch nucleating bubbles. We comment on other kinds of bubbles that could interpolate between the two branches

  1. Ionization and pulse lethargy effects in inverse Cherenkov accelerators

    International Nuclear Information System (INIS)

    Sprangle, P.; Hubbard, R.F.; Hafizi, B.

    1997-01-01

    Ionization processes limit the accelerating gradient and place an upper limit on the pulse duration of the electromagnetic driver in the inverse Cherenkov accelerator (ICA). Group velocity slippage, i.e., pulse lethargy, on the other hand, imposes a lower limit on the pulse duration. These limits are obtained for two ICA configurations in which the electromagnetic driver (e.g., laser or millimeter wave source) is propagated in a waveguide that is (i) lined with a dielectric material or (ii) filled with a neutral gas. In either configuration the electromagnetic driving field is guided and has an axial electric field with phase velocity equal to the speed of light in vacuum, c. The intensity of the driver in the ICA, and therefore the acceleration gradient, is limited by tunneling and collisional ionization effects. Partial ionization of the dielectric liner or gas can lead to significant modification of the dispersive properties of the waveguide, altering the phase velocity of the accelerating field and causing particle slippage, thus disrupting the acceleration process. An additional limitation on the pulse duration is imposed since the group velocity of the driving pulse is less than c and the pulse slips behind the accelerated electrons. Hence for sufficiently short pulses the electrons outrun the pulse, terminating the acceleration. Limitations on the driver pulse duration and accelerating gradient, due to ionization and pulse lethargy, are estimated for the two ICA configurations. Maximum accelerating gradients and pulse durations are presented for a 10 μm, 1 mm, and 1 cm wavelength electromagnetic driver. The combination of ionization and pulse lethargy effects impose severe limitations on the maximum energy gain in inverse Cherenkov accelerators. copyright 1997 The American Physical Society

  2. Disclosed dielectric and electromechanical properties of hydrogenated nitrile–butadiene dielectric elastomer

    International Nuclear Information System (INIS)

    Yang, Dan; Tian, Ming; Dong, Yingchao; Liu, Haoliang; Yu, Yingchun; Zhang, Liqun

    2012-01-01

    This paper presents a comprehensive study of the effects of acrylonitrile content, crosslink density and plasticization on the dielectric and electromechanical performances of hydrogenated nitrile–butadiene dielectric elastomer. It was found that by increasing the acrylonitrile content of hydrogenated nitrile–butadiene dielectric elastomer, the dielectric constant will be improved accompanied with a sharp decrease of electrical breakdown strength leading to a small actuated strain. At a fixed electric field, a high crosslink density increased the elastic modulus of dielectric elastomer, but it also enhanced the electrical breakdown strength leading to a high actuated strain. Adding a plasticizer into the dielectric elastomer decreased the dielectric constant and electrical breakdown strength slightly, but reduced the elastic modulus sharply, which was beneficial for obtaining a large strain at low electric field from the dielectric elastomer. The largest actuated strain of 22% at an electric field of 30 kV mm −1 without any prestrain was obtained. Moreover, the hydrogenated nitrile–butadiene dielectric actuator showed good history dependence. This proposed material has great potential to be an excellent dielectric elastomer. (paper)

  3. Diagnostics for advanced laser acceleration experiments

    Energy Technology Data Exchange (ETDEWEB)

    Misuri, Alessio [Univ. of Pisa (Italy)

    2002-01-01

    The first proposal for plasma based accelerators was suggested by 1979 by Tajima and Dawson. Since then there has been a tremendous progress both theoretically and experimentally. The theoretical progress is particularly due to the growing interest in the subject and to the development of more accurate numerical codes for the plasma simulations (especially particle-in-cell codes). The experimental progress follows from the development of multi-terawatt laser systems based on the chirped-pulse amplification technique. These efforts have produced results in several experiments world-wide, with the detection of accelerated electrons of tens of MeV. The peculiarity of these advanced accelerators is their ability to sustain extremely large acceleration gradients. In the conventional radio frequency linear accelerators (RF linacs) the acceleration gradients are limited roughly to 100 MV/m; this is partially due to breakdown which occurs on the walls of the structure. The electrical breakdown is originated by the emission of the electrons from the walls of the cavity. The electrons cause an avalanche breakdown when they reach other metal parts of the RF linacs structure.

  4. Diagnostics for advanced laser acceleration experiments

    International Nuclear Information System (INIS)

    Misuri, Alessio

    2002-01-01

    The first proposal for plasma based accelerators was suggested by 1979 by Tajima and Dawson. Since then there has been a tremendous progress both theoretically and experimentally. The theoretical progress is particularly due to the growing interest in the subject and to the development of more accurate numerical codes for the plasma simulations (especially particle-in-cell codes). The experimental progress follows from the development of multi-terawatt laser systems based on the chirped-pulse amplification technique. These efforts have produced results in several experiments world-wide, with the detection of accelerated electrons of tens of MeV. The peculiarity of these advanced accelerators is their ability to sustain extremely large acceleration gradients. In the conventional radio frequency linear accelerators (RF linacs) the acceleration gradients are limited roughly to 100 MV/m; this is partially due to breakdown which occurs on the walls of the structure. The electrical breakdown is originated by the emission of the electrons from the walls of the cavity. The electrons cause an avalanche breakdown when they reach other metal parts of the RF linacs structure

  5. Electron depletion via cathode spot dispersion of dielectric powder into an overhead plasma

    International Nuclear Information System (INIS)

    Gillman, Eric D.; Foster, John E.

    2013-01-01

    The effectiveness of cathode spot delivered dielectric particles for the purpose of plasma depletion is investigated. Here, cathode spot flows kinetically entrain and accelerate dielectric particles originally at rest into a background plasma. The time variation of the background plasma density is tracked using a cylindrical Langmuir probe biased approximately at electron saturation. As inferred from changes in the electron saturation current, depletion fractions of up to 95% are observed. This method could be exploited as a means of communications blackout mitigation for manned and unmanned reentering spacecraft as well as any high speed vehicle enveloped by a dense plasma layer

  6. Preinjector for Linac 1, accelerating column

    CERN Multimedia

    1974-01-01

    For a description of the Linac 1 preinjector, please see first 7403070X. High up on the wall of the Faraday cage (7403073X) is this drum-shaped container of the ion source (7403083X). It is mounted at the HV end of the accelerating column through which the ions (usually protons; many other types of ions in the course of its long history) proceed through the Faraday cage wall to the low-energy end (at ground potential) of Linac 1. The 520 kV accelerating voltage was supplied by a SAMES generator (7403074X).

  7. Ultra-high vacuum photoelectron linear accelerator

    Science.gov (United States)

    Yu, David U.L.; Luo, Yan

    2013-07-16

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

  8. Magnetic force induced tristability for dielectric elastomer actuators

    Science.gov (United States)

    Li, Xin-Qiang; Li, Wen-Bo; Zhang, Wen-Ming; Zou, Hong-Xiang; Peng, Zhi-Ke; Meng, Guang

    2017-10-01

    This paper presents a novel dielectric elastomer actuator (DEA) with three stable states. By introducing magnetic forces and coupling them with two cone dielectric elastomer (DE) films, an inherent tristability for the DEA is obtained with a compact design. It is easy to switch between the three stable states by controlling the voltages applied to the DE films. A theoretical model of the system’s potential energy that contains the free energy of the DEs and the potential energy of the applied magnetic field was developed for the tristable mechanism. The experimental results demonstrate that controllable transitions between the three stable states can be achieved with this design by applying over-critical voltages to the various DE films. The maximum dynamic range of the DEA can exceed 53.8% of the total length of the device and the DE’s creep speed was accelerated under the action of the magnetic field.

  9. Computation of Dielectric Response in Molecular Solids for High Capacitance Organic Dielectrics.

    Science.gov (United States)

    Heitzer, Henry M; Marks, Tobin J; Ratner, Mark A

    2016-09-20

    The dielectric response of a material is central to numerous processes spanning the fields of chemistry, materials science, biology, and physics. Despite this broad importance across these disciplines, describing the dielectric environment of a molecular system at the level of first-principles theory and computation remains a great challenge and is of importance to understand the behavior of existing systems as well as to guide the design and synthetic realization of new ones. Furthermore, with recent advances in molecular electronics, nanotechnology, and molecular biology, it has become necessary to predict the dielectric properties of molecular systems that are often difficult or impossible to measure experimentally. In these scenarios, it is would be highly desirable to be able to determine dielectric response through efficient, accurate, and chemically informative calculations. A good example of where theoretical modeling of dielectric response would be valuable is in the development of high-capacitance organic gate dielectrics for unconventional electronics such as those that could be fabricated by high-throughput printing techniques. Gate dielectrics are fundamental components of all transistor-based logic circuitry, and the combination high dielectric constant and nanoscopic thickness (i.e., high capacitance) is essential to achieving high switching speeds and low power consumption. Molecule-based dielectrics offer the promise of cheap, flexible, and mass producible electronics when used in conjunction with unconventional organic or inorganic semiconducting materials to fabricate organic field effect transistors (OFETs). The molecular dielectrics developed to date typically have limited dielectric response, which results in low capacitances, translating into poor performance of the resulting OFETs. Furthermore, the development of better performing dielectric materials has been hindered by the current highly empirical and labor-intensive pace of synthetic

  10. Appearance of a conductive carbonaceous coating in a CO2 dielectric barrier discharge and its influence on the electrical properties and the conversion efficiency

    International Nuclear Information System (INIS)

    Belov, Igor; Paulussen, Sabine; Bogaerts, Annemie

    2016-01-01

    This work examines the properties of a dielectric barrier discharge (DBD) reactor, built for CO 2 decomposition, by means of electrical characterization, optical emission spectroscopy and gas chromatography. The discharge, formed in an electronegative gas (such as CO 2 , but also O 2 ), exhibits clearly different electrical characteristics, depending on the surface conductivity of the reactor walls. An asymmetric current waveform is observed in the metal-dielectric (MD) configuration, with sparse high-current pulses in the positive half-cycle (HC) and a more uniform regime in the negative HC. This indicates that the discharge is operating in two alternating regimes with rather different properties. At high CO 2 conversion regimes, a conductive coating is deposited on the dielectric. This so-called coated MD configuration yields a symmetric current waveform, with current peaks in both the positive and negative HCs. In a double-dielectric (DD) configuration, the current waveform is also symmetric, but without current peaks in both the positive and negative HC. Finally, the DD configuration with conductive coating on the inner surface of the outer dielectric, i.e. so-called coated DD, yields again an asymmetric current waveform, with current peaks in the negative HC. These different electrical characteristics are related to the presence of the conductive coating on the dielectric wall of the reactor and can be explained by an increase of the local barrier capacitance available for charge transfer. The different discharge regimes affect the CO 2 conversion, more specifically, the CO 2 conversion is lowest in the clean DD configuration. It is somewhat higher in the coated DD configuration, and still higher in the MD configuration. The clean and coated MD configuration, however, gave similar CO 2 conversion. These results indicate that the conductivity of the dielectric reactor walls can highly promote the development of the high-amplitude discharge current pulses and

  11. Rotational Response of Toe-Restrained Retaining Walls to Earthquake Ground Motions

    National Research Council Canada - National Science Library

    Ebeling, Robert M; White, Barry C

    2006-01-01

    .... The PC software CorpsWallRotate (sometimes referred to as CWRotate) was developed to perform an analysis of permanent wall rotation for each proposed retaining wall section to a user-specified earthquake acceleration time-history...

  12. Dielectric capacitors with three-dimensional nanoscale interdigital electrodes for energy storage.

    Science.gov (United States)

    Han, Fangming; Meng, Guowen; Zhou, Fei; Song, Li; Li, Xinhua; Hu, Xiaoye; Zhu, Xiaoguang; Wu, Bing; Wei, Bingqing

    2015-10-01

    Dielectric capacitors are promising candidates for high-performance energy storage systems due to their high power density and increasing energy density. However, the traditional approach strategies to enhance the performance of dielectric capacitors cannot simultaneously achieve large capacitance and high breakdown voltage. We demonstrate that such limitations can be overcome by using a completely new three-dimensional (3D) nanoarchitectural electrode design. First, we fabricate a unique nanoporous anodic aluminum oxide (AAO) membrane with two sets of interdigitated and isolated straight nanopores opening toward opposite planar surfaces. By depositing carbon nanotubes in both sets of pores inside the AAO membrane, the new dielectric capacitor with 3D nanoscale interdigital electrodes is simply realized. In our new capacitors, the large specific surface area of AAO can provide large capacitance, whereas uniform pore walls and hemispheric barrier layers can enhance breakdown voltage. As a result, a high energy density of 2 Wh/kg, which is close to the value of a supercapacitor, can be achieved, showing promising potential in high-density electrical energy storage for various applications.

  13. Dielectric properties of electron irradiated PbZrO 3 thin films

    Indian Academy of Sciences (India)

    The present paper deals with the study of the effects of electron (8 MeV) irradiation on the dielectric and ferroelectric properties of PbZrO3 thin films grown by sol–gel technique. The films were (0.62 m thick) subjected to electron irradiation using Microtron accelerator (delivered dose 80, 100, 120 kGy). The films were well ...

  14. Wall-Current-Monitor based Ghost and Satellite Bunch Detection in the CERN PS and the LHC Accelerators

    CERN Document Server

    Steinhagen, R J; Belleman, J; Bohl, T; Damerau, H

    2012-01-01

    While most LHC detectors and instrumentation systems are optimised for a nominal bunch spacing of 25 ns, the LHC RF cavities themselves operate at the 10th harmonic of the maximum bunch frequency. Due to the beam production scheme and transfers in the injector chain, part of the nominally ‘empty’ RF buckets may contain particles, referred to as ghost or satellite bunches. These populations must be accurately quantified for high-precision experiments, luminosity calibration and control of parasitic particle encounters at the four LHC interaction points. This contribution summarises the wall-current-monitor based ghost and satellite bunch measurements in CERN’s PS and LHC accelerators. Instrumentation set-up, post-processing and achieved performance are discussed.

  15. Dielectric characterization of high-performance spaceflight materials

    Science.gov (United States)

    Kleppe, Nathan; Nurge, Mark A.; Bowler, Nicola

    2015-03-01

    As commercial space travel increases, the need for reliable structural health monitoring to predict possible weaknesses or failures of structural materials also increases. Monitoring of these materials can be done through the use of dielectric spectroscopy by comparing permittivity or conductivity measurements performed on a sample in use to that of a pristine sample from 100 μHz to 3 GHz. Fluctuations in these measured values or of the relaxation frequencies, if present, can indicate chemical or physical changes occurring within the material and the possible need for maintenance/replacement. In this work, we establish indicative trends that occur due to changes in dielectric spectra during accelerated aging of various high-performance polymeric materials: ethylene vinyl alcohol (EVOH), Poly (ether ether ketone) (PEEK), polyphenylene sulfide (PPS), and ultra-high molecular weight polyethylene (UHMWPE). Uses for these materials range from electrical insulation and protective coatings to windows and air- or space-craft parts that may be subject to environmental damage over long-term operation. Samples were prepared by thermal exposure and, separately, by ultraviolet/water-spray cyclic aging. The aged samples showed statistically-significant trends of either increasing or decreasing real or imaginary permittivity values, relaxation frequencies, conduction or the appearance of new relaxation modes. These results suggest that dielectric testing offers the possibility of nondestructive evaluation of the extent of age-related degradation in these materials.

  16. Nuclear fusion ion beam source composed of optimum channel wall

    International Nuclear Information System (INIS)

    Furukaw, T.

    2007-01-01

    Full text of publication follows: Numerical and experimental researches of the hall-type beam accelerator was conducted by highlighting both neutral species and material of acceleration channel wall. The hall-type beam accelerator is expected as ion beam source for nuclear fusion since it could product ion beam density over 10 3 times as high as that of electrostatic accelerator, which is used regularly as beam heating device, because it is proven that the beam heating method could accelerate ion to high energy beam by electric field and heat plasma to ultra high temperature of 100 million degrees or more. At high-voltage mode of DC regime that is normal operational condition, however, the various plasma MHD (magneto-hydrodynamic) instabilities are generated. In particular, the large-amplitude and low-frequency plasma MHD instability in the tens of kHz among them has been a serious problem that should be solved to improve the operational stability and the system durability. So, we propose a hall-type beam accelerator with new design concepts; both acquisition of simultaneous solution for reducing the plasma MHD instability and the accelerator core overheating and optimum combination of the acceleration channel wall material. The technologies for this concept are as follows: 1) To increase neutral species velocity-inlet in acceleration channel by preheating propellant through circularly propellant conduit line inside accelerator system could bring about the lower amplitude of the instability. 2) Through this method, the accelerator system is cooled, and the higher thrust and specific-impulse is produced with hardly changing thrust efficiency at the same time. 3) To select BN (Boron- Nitride) and Al 2 O 3 as wall material of ionization- and acceleration-zone in acceleration channel respectively having different secondary-electron emission-coefficient could achieve the higher-efficiency and -durability. The hall-type beam accelerator designed using these technologies

  17. Experimental Studies of W-Band Accelerator Structures at High Field

    Energy Technology Data Exchange (ETDEWEB)

    Hill, Marc E

    2001-02-09

    A high-gradient electron accelerator is desired for high-energy physics research, where frequency scalings of breakdown and trapping of itinerant beamline particles dictates operation of the accelerator at short wavelengths. The first results of design and test of a high-gradient mm-wave linac with an operating frequency at 91.392 GHz (W-band) are presented. A novel approach to particle acceleration is presented employing a planar, dielectric lined waveguide used for particle acceleration. The traveling wave fields in the planar dielectric accelerator (PDA) are analyzed for an idealized structure, along with a circuit equivalent model used for understanding the structure as a microwave circuit. Along with the W-band accelerator structures, other components designed and tested are high power rf windows, high power attenuators, and a high power squeeze-type phase shifter. The design of the accelerator and its components where eased with the aide of numerical simulations using a finite-difference electromagnetic field solver. Manufacturing considerations of the small, delicate mm-wave components and the steps taken to reach a robust fabrication process are detailed. These devices were characterized under low power using a two-port vector network analyzer to verify tune and match, including measurements of the structures' fields using a bead-pull. The measurements are compared with theory throughout. Addition studies of the W-band structures were performed under high power utilizing a 11.424 GHz electron linac as a current source. Test results include W-band power levels of 200 kW, corresponding to fields in the PDA of over 20 MV/m, a higher gradient than any collider. Planar accelerator devices naturally have an rf quadrupole component of the accelerating field. Presented for the first time are the measurements of this effect.

  18. van der Waals interaction between a microparticle and a single-walled carbon nanotube

    International Nuclear Information System (INIS)

    Blagov, E. V.; Mostepanenko, V. M.; Klimchitskaya, G. L.

    2007-01-01

    The Lifshitz-type formulas describing the free energy and the force of the van der Waals interaction between an atom (molecule) and a single-walled carbon nanotube are obtained. The single-walled nanotube is considered as a cylindrical sheet carrying a two-dimensional free-electron gas with appropriate boundary conditions on the electromagnetic field. The obtained formulas are used to calculate the van der Waals free energy and force between a hydrogen atom (molecule) and single-walled carbon nanotubes of different radii. Comparison studies of the van der Waals interaction of hydrogen atoms with single-walled and multiwalled carbon nanotubes show that depending on atom-nanotube separation distance, the idealization of graphite dielectric permittivity is already applicable to nanotubes with only two or three walls

  19. Photoelectron linear accelerator for producing a low emittance polarized electron beam

    Science.gov (United States)

    Yu, David U.; Clendenin, James E.; Kirby, Robert E.

    2004-06-01

    A photoelectron linear accelerator for producing a low emittance polarized electric beam. The accelerator includes a tube having an inner wall, the inner tube wall being coated by a getter material. A portable, or demountable, cathode plug is mounted within said tube, the surface of said cathode having a semiconductor material formed thereon.

  20. Hollow-core photonic band gap fibers for particle acceleration

    Directory of Open Access Journals (Sweden)

    Robert J. Noble

    2011-12-01

    Full Text Available Photonic band gap (PBG dielectric fibers with hollow cores are being studied both theoretically and experimentally for use as laser driven accelerator structures. The hollow core functions as both a longitudinal waveguide for the transverse-magnetic (TM accelerating fields and a channel for the charged particles. The dielectric surrounding the core is permeated by a periodic array of smaller holes to confine the mode, forming a photonic crystal fiber in which modes exist in frequency passbands, separated by band gaps. The hollow core acts as a defect which breaks the crystal symmetry, and so-called defect, or trapped modes having frequencies in the band gap will only propagate near the defect. We describe the design of 2D hollow-core PBG fibers to support TM defect modes with high longitudinal fields and high characteristic impedance. Using as-built dimensions of industrially made fibers, we perform a simulation analysis of prototype PBG fibers with dimensions appropriate for speed-of-light TM modes.

  1. Harp, a short pulse, high current electron beam accelerator

    International Nuclear Information System (INIS)

    Prestwich, K.R.

    1974-01-01

    A 3 MV, 800 kA, 24 ns electron beam accelerator is described and the results of initial switching experiments are discussed. The generator will provide a source for studying the physics of processes leading to electron beam driven, inertially confined fusion. The major components of the accelerator are two diodes with a common anode, twelve oil-dielectric Blumleins with low jitter (less than 2 ns) multichannel switches, three intermediate storage capacitors, a trigger pulse generator and two Marx generators. (U.S.)

  2. Streaming vorticity flux from oscillating walls with finite amplitude

    Science.gov (United States)

    Wu, J. Z.; Wu, X. H.; Wu, J. M.

    1993-01-01

    How to describe vorticity creation from a moving wall is a long standing problem. This paper discusses relevant issues at the fundamental level. First, it is shown that the concept of 'vorticity flux due to wall acceleration' can be best understood by following fluid particles on the wall rather than observing the flow at fixed spatial points. This is of crucial importance when the time-averaged flux is to be considered. The averaged flux has to be estimated in a wall-fixed frame of reference (in which there is no flux due to wall acceleration at all); or, if an inertial frame of reference is used, the generalized Lagrangian mean (GLM) also gives the same result. Then, for some simple but typical configurations, the time-averaged vorticity flux from a harmonically oscillating wall with finite amplitude is analyzed, without appealing to small perturbation. The main conclusion is that the wall oscillation will produce an additional mean vorticity flux (a fully nonlinear streaming effect), which is partially responsible for the mechanism of vortex flow control by waves. The results provide qualitative explanation for some experimentally and/or computationally observed phenomena.

  3. Peculiarities of low-frequency dielectric spectra and domain wall motion in gadolinium molybdate

    International Nuclear Information System (INIS)

    Galiyarova, N.M.; Gorin, S.V.; Dontsova, L.I.; Shil'nikov, A.V.; Shuvalov, L.A.

    1994-01-01

    Low-frequency Debye dispersion of dielectric permeability in GMO with the low values of high-frequency limit ε ∞ was investigated in a wide temperature range as well as in fields of variable amplitude. The features of domain boundaries motion were studied at the partial repolarization in monopolar P-pulsed fields. The model of cooperationrelaxation motion brifing in parallel with positive to negative contribution to polarization that explained the low values of ε ∞ was suggested

  4. Effect of accelerated matter in neutron optics

    International Nuclear Information System (INIS)

    Frank, A. I.; Geltenbort, P.; Jentschel, M.; Kustov, D. V.; Kulin, G. V.; Nosov, V. G.; Strepetov, A. N.

    2008-01-01

    Results of experiments aimed at observing the change in the energy of a neutron traversing an accelerated refractive sample are reported. The experiments were performed with ultracold neutrons, the energy transfer in these experiments being ±(2-6) x 10 -10 eV. The results suggest the existence of the effect and agree with theoretical predictions to a precision higher than 10%. A similar effect was previously predicted for the change in the frequency of an electromagnetic wave traversing an accelerated dielectric slab. In all probability, the effect has a very general nature, but it is presently observed only in neutron optics.

  5. Dynamics of plane-symmetric thin walls in general relativity

    International Nuclear Information System (INIS)

    Wang, A.

    1992-01-01

    Plane walls (including plane domain walls) without reflection symmetry are studied in the framework of Einstein's general relativity. Using the distribution theory, all the Einstein field equations and Bianchi identities are split into two groups: one holding in the regions outside of the wall and the other holding at the wall. The Einstein field equations at the wall are found to take a very simple form, and given explicitly in terms of the discontinuities of the metric coefficients and their derivatives. The Bianchi identities at the wall are also given explicitly. Using the latter, the interaction of a plane wall with gravitational waves and some specific matter fields is studied. In particular, it is found that, when a gravitational plane wave passes through a wall, if the wall has no reflection symmetry, the phenomena, such as reflection, stimulation, or absorption, in general, occur. It is also found that, unlike for gravitational waves, a massless scalar wave or an electromagnetic wave continuously passes through a wall without any reflection. The repulsion and attraction of a plane wall are also studied. It is found that the acceleration of an observer who is at rest relative to the wall usually consists of three parts: one is due to the force produced by the wall, the second is due to the force produced by the space-time curvature, which is zero if the wall has reflection symmetry, and the last is due to the accelerated motion of the wall. As a result, a repulsive (attractive) plane wall may not be repulsive (attractive) at all. Finally, the collision and interaction among the walls are studied

  6. Simulation analysis of rectangular dielectric-loaded traveling wave amplifiers for THz sources

    Directory of Open Access Journals (Sweden)

    Changbiao Wang

    2007-12-01

    Full Text Available Nonlinear simulation results for a 220-GHz rectangular dielectric-loaded traveling-wave amplifier are presented. Simulations are used to check a linear theory that is developed by phenomenological introduction of an effective dielectric parameter for electron beam channel, and it is found that the rf power gains from Pierce three-wave theory and particle simulations are in reasonable agreement. It is shown that the rf power gain during initial beam-wave interaction is positive; the falling on the initial rf power profile, which has been thought to be the rf power transferred to the beam for bunching buildup (negative gain effect, is probably resulting from numerical errors. Beam-wave interaction mechanism is analyzed by examining the evolution of beam bunching centers. Influences of various parameters on amplifier performance are examined, and transverse space-charge effect is analyzed. A symmetric excitation scheme for rf couplers is proposed, and rf field jumps on the common intersection line of vacuum, dielectric, and metal wall, which were found in rf simulations, are explained theoretically.

  7. High frequency single mode traveling wave structure for particle acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Ivanyan, M.I.; Danielyan, V.A.; Grigoryan, B.A.; Grigoryan, A.H. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Tsakanian, A.V. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Technische Universität Darmstadt, Institut TEMF, 64289 Darmstadt (Germany); Tsakanov, V.M., E-mail: tsakanov@asls.candle.am [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Vardanyan, A.S.; Zakaryan, S.V. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia)

    2016-09-01

    The development of the new high frequency slow traveling wave structures is one of the promising directions in accomplishment of charged particles high acceleration gradient. The disc and dielectric loaded structures are the most known structures with slowly propagating modes. In this paper a large aperture high frequency metallic two-layer accelerating structure is studied. The electrodynamical properties of the slowly propagating TM{sub 01} mode in a metallic tube with internally coated low conductive thin layer are examined.

  8. Laser-powered dielectric-structures for the production of high-brightness electron and x-ray beams

    Science.gov (United States)

    Travish, Gil; Yoder, Rodney B.

    2011-05-01

    Laser powered accelerators have been under intensive study for the past decade due to their promise of high gradients and leveraging of rapid technological progress in photonics. Of the various acceleration schemes under examination, those based on dielectric structures may enable the production of relativistic electron beams in breadbox sized systems. When combined with undulators having optical-wavelength periods, these systems could produce high brilliance x-rays which find application in, for instance, medical and industrial imaging. These beams also may open the way for table-top atto-second sciences. Development and testing of these dielectric structures faces a number of challenges including complex beam dynamics, new demands on lasers and optical coupling, beam injection schemes, and fabrication. We describe one approach being pursued at UCLA-the Micro Accelerator Platform (MAP). A structure similar to the MAP has also been designed which produces periodic deflections and acts as an undulator for radiation production, and the prospects for this device will be considered. The lessons learned from the multi-year effort to realize these devices will be presented. Challenges remain with acceleration of sub-relativistic beams, focusing, beam phase stability and extension of these devices to higher beam energies. Our progress in addressing these hurdles will be summarized. Finally, the demands on laser technology and optical coupling will be detailed.

  9. Pre-breakdown processes in a dielectric fluid in inhomogeneous pulsed electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Shneider, Mikhail N., E-mail: m.n.shneider@gmail.com [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Pekker, Mikhail [MMSolution, 6808 Walker Street, Philadelphia, Pennsylvania 19135 (United States)

    2015-06-14

    We consider the development of pre-breakdown cavitation nanopores appearing in the dielectric fluid under the influence of the electrostrictive stresses in the inhomogeneous pulsed electric field. It is shown that three characteristic regions can be distinguished near the needle electrode. In the first region, where the electric field gradient is greatest, the cavitation nanopores, occurring during the voltage nanosecond pulse, may grow to the size at which an electron accelerated by the field inside the pores can acquire enough energy for excitation and ionization of the liquid on the opposite pore wall, i.e., the breakdown conditions are satisfied. In the second region, the negative pressure caused by the electrostriction is large enough for the cavitation initiation (which can be registered by optical methods), but, during the voltage pulse, the pores do not reach the size at which the potential difference across their borders becomes sufficient for ionization or excitation of water molecules. And, in the third, the development of cavitation is impossible, due to an insufficient level of the negative pressure: in this area, the spontaneously occurring micropores do not grow and collapse under the influence of surface tension forces. This paper discusses the expansion dynamics of the cavitation pores and their most probable shape.

  10. At site qualification of accelerating tube dynodes

    International Nuclear Information System (INIS)

    Rajan, Rehim N.; Dewangan, S.; Sharma, D.K.

    2015-01-01

    A dc electron beam accelerator rated for 3 MeV encountered numerous vacuum side discharges at terminal voltage levels of 1800 kV. The cumulative rating of the accelerating tube in the system is 3350 kV. Pulsed currents in the order of 50 mA has been observed at the beam collector during these events along with voltage dips in terminal voltage. As dynode to dynode arcing is suspected to be the primary cause of this behaviour, it is desired to test the voltage withstanding capacity of each pair of dynodes. The accelerating tubes are rated for 335 kV at 6 kg/cm 2 SF 6 environment. However working at these pressures and testing of individual pairs of dynodes are impractical for qualification of dynodes of the 10 sets of accelerating tubes mounted in the accelerator. This problem has been overcome by using atmospheric pressure SF 6 and solid dielectrics. Experience of at site testing of the accelerating tube dynodes are described in this paper. (author)

  11. Dressed Domain Walls and holography

    International Nuclear Information System (INIS)

    Grisa, Luca; Pujolas, Oriol

    2008-01-01

    The cutoff version of the AdS/CFT correspondence states that the Randall Sundrum scenario is dual to a Conformal Field Theory (CFT) coupled to gravity in four dimensions. The gravitational field produced by relativistic Domain Walls can be exactly solved in both sides of the correspondence, and thus provides one further check of it. We show in the two sides that for the most symmetric case, the wall motion does not lead to particle production of the CFT fields. Still, there are nontrivial effects. Due to the trace anomaly, the CFT effectively renormalizes the Domain Wall tension. On the five dimensional side, the wall is a codimension 2 brane localized on the Randall-Sundrum brane, which pulls the wall in a uniform acceleration. This is perceived from the brane as a Domain Wall with a tension slightly larger than its bare value. In both cases, the deviation from General Relativity appears at nonlinear level in the source, and the leading corrections match to the numerical factors.

  12. Dielectric Elastomers for Fluidic and Biomedical Applications

    Science.gov (United States)

    McCoul, David James

    Dielectric elastomers have demonstrated tremendous potential as high-strain electromechanical transducers for a myriad of novel applications across all engineering disciplines. Because their soft, viscoelastic mechanical properties are similar to those of living tissues, dielectric elastomers have garnered a strong foothold in a plethora of biomedical and biomimetic applications. Dielectric elastomers consist of a sheet of stretched rubber, or elastomer, coated on both sides with compliant electrode materials; application of a voltage generates an electrostatic pressure that deforms the elastomer. They can function as soft generators, sensors, or actuators, and this last function is the focus of this dissertation. Many design configurations are possible, such as stacks, minimum energy structures, interpenetrating polymer networks, shape memory dielectric elastomers, and others; dielectric elastomers are already being applied to many fields of biomedicine. The first part of the original research presented in this dissertation details a PDMS microfluidic system paired with a dielectric elastomer stack actuator of anisotropically prestrained VHB(TM) 4910 (3M(TM)) and single-walled carbon nanotubes. These electroactive microfluidic devices demonstrated active increases in microchannel width when 3 and 4 kV were applied. Fluorescence microscopy also indicated an accompanying increase in channel depth with actuation. The cross-sectional area strains at 3 and 4 kV were approximately 2.9% and 7.4%, respectively. The device was then interfaced with a syringe pump, and the pressure was measured upstream. Linear pressure-flow plots were developed, which showed decreasing fluidic resistance with actuation, from 0.192 psi/(microL/min) at 0 kV, to 0.160 and 0.157 psi/(microL/min) at 3 and 4 kV, respectively. This corresponds to an ~18% drop in fluidic resistance at 4 kV. Active de-clogging was tested in situ with the device by introducing ~50 microm diameter PDMS microbeads and

  13. Nonlinear dielectric response in ferroelectric thin films

    Directory of Open Access Journals (Sweden)

    Lente, M. H.

    2004-08-01

    Full Text Available Electrical permittivity dependence on electric external bias field was investigated in PZT thin films. The results revealed the existence of two mechanisms contributing to the electrical permittivity. The first one was related to the domain reorientation, which was responsible for a strong no linear dielectric behavior, acting only during the poling process. The second mechanism was associated with the domain wall vibrations, which presented a reasonable linear electrical behavior with the applied bias field, contributing always to the permittivity independently of the poling state of the sample. The results also indicated that the gradual reduction of the permittivity with the increase of the bias field strength may be related to the gradual bending of the domain walls. It is believed that the domain wall bending induces a hardening and/or a thinning of the walls, thus reducing the electrical permittivity. A reinterpretation of the model proposed in the literature to explain the dielectric characteristics of ferroelectric materials at high electric field regime is proposed.

    Se ha estudiado la dependencia de la permitividad eléctrica con un campo bias externo en láminas delgadas de PZT. Los resultados revelaron la existencia de dos mecanismos que contribuyen a la permitividad eléctrica. El primero está relacionado con la reorientación de dominios, actúa sólo durante el proceso de polarización y es responsable de un comportamiento dieléctrico fuertemente no lineal. El segundo mecanismo se asocia a las vibraciones de las paredes de dominio, presentando un comportamiento eléctrico razonablemente lineal con el campo bias aplicado, contribuyendo siempre a la permitividad independientemente del estado de polarización de la muestra. Los resultados indicaron también que la reducción gradual de la permitividad con el aumento de la fuerza del campo bias podría estar relacionada con el “bending” gradual de las paredes de dominio

  14. Dispersion of Dielectric Permittivity in a Nanocrystalline Cellulose-Triglycine Sulfate Composite at Low and Ultralow Frequencies

    Science.gov (United States)

    Thu'o'ng, Nguyen Hoai; Sidorkin, A. S.; Milovidova, S. D.

    2018-03-01

    The dispersion of dielectric permittivity in nanocrystalline cellulose-triglycine sulfate composites is studied in the range of frequencies from 10-3 to 106 Hz, at temperatures varying from room temperature to the temperature of phase transition in this composite (54°C), in weak electric fields (1 V cm-1). Two behaviors for the dielectric dispersion are identified in the studied frequency range: at ultralow frequencies (10-3-10 Hz), the dispersion is due to Maxwell-Wagner polarization, while at higher frequencies (10-106 Hz), the dispersion is due to the movement of domain walls in the embedded triglycine sulfate crystallites. An additional peak in the temperature-dependent profiles of dielectric permittivity is detected at lower temperatures in freshly prepared samples of the considered composite; we associate it with the presence of residual water in these samples.

  15. Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Yanfeng; Pan, Chengbin; Hui, Fei; Shi, Yuanyuan; Lanza, Mario, E-mail: mlanza@suda.edu.cn [Institute of Functional Nano and Soft Materials, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren-Ai Road, Suzhou 215123 (China); Zhang, Meiyun; Long, Shibing [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Lian, Xiaojuan; Miao, Feng [National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Larcher, Luca [DISMI, Università di Modena e Reggio Emilia, 42122 Reggio Emilia (Italy); Wu, Ernest [IBM Research Division, Essex Junction, Vermont 05452 (United States)

    2016-01-04

    Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO{sub 2}, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications.

  16. Polymer/metal oxide hybrid dielectrics for low voltage field-effect transistors with solution-processed, high-mobility semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Held, Martin; Schießl, Stefan P.; Gannott, Florentina [Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen D-91058 (Germany); Institute for Physical Chemistry, Universität Heidelberg, Heidelberg D-69120 (Germany); Miehler, Dominik [Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen D-91058 (Germany); Zaumseil, Jana, E-mail: zaumseil@uni-heidelberg.de [Institute for Physical Chemistry, Universität Heidelberg, Heidelberg D-69120 (Germany)

    2015-08-24

    Transistors for future flexible organic light-emitting diode (OLED) display backplanes should operate at low voltages and be able to sustain high currents over long times without degradation. Hence, high capacitance dielectrics with low surface trap densities are required that are compatible with solution-processable high-mobility semiconductors. Here, we combine poly(methyl methacrylate) (PMMA) and atomic layer deposition hafnium oxide (HfO{sub x}) into a bilayer hybrid dielectric for field-effect transistors with a donor-acceptor polymer (DPPT-TT) or single-walled carbon nanotubes (SWNTs) as the semiconductor and demonstrate substantially improved device performances for both. The ultra-thin PMMA layer ensures a low density of trap states at the semiconductor-dielectric interface while the metal oxide layer provides high capacitance, low gate leakage and superior barrier properties. Transistors with these thin (≤70 nm), high capacitance (100–300 nF/cm{sup 2}) hybrid dielectrics enable low operating voltages (<5 V), balanced charge carrier mobilities and low threshold voltages. Moreover, the hybrid layers substantially improve the bias stress stability of the transistors compared to those with pure PMMA and HfO{sub x} dielectrics.

  17. Lattices of dielectric resonators

    CERN Document Server

    Trubin, Alexander

    2016-01-01

    This book provides the analytical theory of complex systems composed of a large number of high-Q dielectric resonators. Spherical and cylindrical dielectric resonators with inferior and also whispering gallery oscillations allocated in various lattices are considered. A new approach to S-matrix parameter calculations based on perturbation theory of Maxwell equations, developed for a number of high-Q dielectric bodies, is introduced. All physical relationships are obtained in analytical form and are suitable for further computations. Essential attention is given to a new unified formalism of the description of scattering processes. The general scattering task for coupled eigen oscillations of the whole system of dielectric resonators is described. The equations for the  expansion coefficients are explained in an applicable way. The temporal Green functions for the dielectric resonator are presented. The scattering process of short pulses in dielectric filter structures, dielectric antennas  and lattices of d...

  18. Two-phase mixed media dielectric with macro dielectric beads for enhancing resistivity and breakdown strength

    Science.gov (United States)

    Falabella, Steven; Meyer, Glenn A; Tang, Vincent; Guethlein, Gary

    2014-06-10

    A two-phase mixed media insulator having a dielectric fluid filling the interstices between macro-sized dielectric beads packed into a confined volume, so that the packed dielectric beads inhibit electro-hydrodynamically driven current flows of the dielectric liquid and thereby increase the resistivity and breakdown strength of the two-phase insulator over the dielectric liquid alone. In addition, an electrical apparatus incorporates the two-phase mixed media insulator to insulate between electrical components of different electrical potentials. And a method of electrically insulating between electrical components of different electrical potentials fills a confined volume between the electrical components with the two-phase dielectric composite, so that the macro dielectric beads are packed in the confined volume and interstices formed between the macro dielectric beads are filled with the dielectric liquid.

  19. Charged particle beam scanning using deformed high gradient insulator

    Science.gov (United States)

    Chen, Yu -Jiuan

    2015-10-06

    Devices and methods are provided to allow rapid deflection of a charged particle beam. The disclosed devices can, for example, be used as part of a hadron therapy system to allow scanning of a target area within a patient's body. The disclosed charged particle beam deflectors include a dielectric wall accelerator (DWA) with a hollow center and a dielectric wall that is substantially parallel to a z-axis that runs through the hollow center. The dielectric wall includes one or more deformed high gradient insulators (HGIs) that are configured to produce an electric field with an component in a direction perpendicular to the z-axis. A control component is also provided to establish the electric field component in the direction perpendicular to the z-axis and to control deflection of a charged particle beam in the direction perpendicular to the z-axis as the charged particle beam travels through the hollow center of the DWA.

  20. Characterization of dielectric materials

    Energy Technology Data Exchange (ETDEWEB)

    King, Danny J.; Babinec, Susan; Hagans, Patrick L.; Maxey, Lonnie C.; Payzant, Edward A.; Daniel, Claus; Sabau, Adrian S.; Dinwiddie, Ralph B.; Armstrong, Beth L.; Howe, Jane Y.; Wood, III, David L.; Nembhard, Nicole S.

    2017-06-27

    A system and a method for characterizing a dielectric material are provided. The system and method generally include applying an excitation signal to electrodes on opposing sides of the dielectric material to evaluate a property of the dielectric material. The method can further include measuring the capacitive impedance across the dielectric material, and determining a variation in the capacitive impedance with respect to either or both of a time domain and a frequency domain. The measured property can include pore size and surface imperfections. The method can still further include modifying a processing parameter as the dielectric material is formed in response to the detected variations in the capacitive impedance, which can correspond to a non-uniformity in the dielectric material.

  1. Planned Enhanced Wakefield Transformer Ratio Experiment at Argonne Wakefield Accelerator

    CERN Document Server

    Kanareykin, Alex; Gai, Wei; Jing, Chunguang; Konecny, Richard; Power, John G

    2005-01-01

    In this paper, we present a preliminary experimental study of a wakefield accelerating scheme that uses a carefully spaced and current ramped electron pulse train to produce wakefields that increases the transformer ratio much higher than 2. A dielectric structure was designed and fabricated to operate at 13.625 GHz with dielectric constant of 15.7. The structure will be initially excited by two beams with first and second beam charge ratio of 1:3. The expected transformer ratio is 3 and the setup can be easily extend to 4 pulses which leads to a transformer ratio of more than 6. The dielectric structure cold test results show the tube is within the specification. A set of laser splitters was also tested to produce ramped bunch train of 2 - 4 pulses. Overall design of the experiment and initial results will be presented.

  2. Role of laser contrast and foil thickness in target normal sheath acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Gizzi, L.A. [ILIL, Istituto Nazionale di Ottica, CNR, Via G. Moruzzi 1, Pisa (Italy); INFN Sezione di Pisa, Largo Pontecorvo 3, 56127 Pisa (Italy); Altana, C. [Dipartimento di Fisica e Astronomia, Università degli Studi di Catania (Italy); Laboratori Nazionali del Sud, INFN, Via S. Sofia, Catania (Italy); Brandi, F. [ILIL, Istituto Nazionale di Ottica, CNR, Via G. Moruzzi 1, Pisa (Italy); Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova (Italy); Cirrone, P. [Laboratori Nazionali del Sud, INFN, Via S. Sofia, Catania (Italy); Cristoforetti, G. [ILIL, Istituto Nazionale di Ottica, CNR, Via G. Moruzzi 1, Pisa (Italy); Fazzi, A. [Energy Department, Polytechnic of Milan, Milan (Italy); INFN, Milan (Italy); Ferrara, P.; Fulgentini, L. [ILIL, Istituto Nazionale di Ottica, CNR, Via G. Moruzzi 1, Pisa (Italy); Giove, D. [INFN-LASA, Via Fratelli Cervi 201, 20090 Segrate (Italy); Koester, P. [ILIL, Istituto Nazionale di Ottica, CNR, Via G. Moruzzi 1, Pisa (Italy); Labate, L. [ILIL, Istituto Nazionale di Ottica, CNR, Via G. Moruzzi 1, Pisa (Italy); INFN Sezione di Pisa, Largo Pontecorvo 3, 56127 Pisa (Italy); Lanzalone, G. [Laboratori Nazionali del Sud, INFN, Via S. Sofia, Catania (Italy); Università degli Studi di Enna Kore, Via delle Olimpiadi, 94100 Enna (Italy); Londrillo, P. [INAF–Osservatorio astronomico Bologna (Italy); Mascali, D.; Muoio, A. [Laboratori Nazionali del Sud, INFN, Via S. Sofia, Catania (Italy); Palla, D. [ILIL, Istituto Nazionale di Ottica, CNR, Via G. Moruzzi 1, Pisa (Italy); INFN Sezione di Pisa, Largo Pontecorvo 3, 56127 Pisa (Italy); Dipartimento di Fisica, Università di Pisa (Italy); Schillaci, F. [Laboratori Nazionali del Sud, INFN, Via S. Sofia, Catania (Italy); Sinigardi, S. [Dipartimento di Fisica e Astronomia, Università di Bologna, Bologna (Italy); INFN, Sez. di Bologna, Via Irnerio 46, 40126 Bologna (Italy); and others

    2016-09-01

    In this paper we present an experimental investigation of laser driven light-ion acceleration using the ILIL laser at an intensity of 2×10{sup 19} W/cm{sup 2}. In the experiment we focused our attention on the identification of the role of target thickness and resistivity in the fast electron transport and in the acceleration process. Here we describe the experimental results concerning the effect of laser contrast in the laser–target interaction regime. We also show preliminary results on ion acceleration which provide information about the role of bulk target ions and surface ions and target dielectric properties in the acceleration process.

  3. Heavy ion accelerating structure

    International Nuclear Information System (INIS)

    Pottier, Jacques.

    1977-01-01

    The heavy ion accelerating structure concerned in this invention is of the kind that have a resonance cavity inside which are located at least two longitudinal conducting supports electrically connected to the cavity by one of their ends in such a way that they are in quarter-wavelength resonance and in phase opposition. Slide tubes are electrically connected alternatively to one or the other of the two supports, they being electrically connected respectively to one or the other end of the side wall of the cavity. The feature of the structure is that it includes two pairs of supports symmetrically placed with respect to the centre line of the cavity, the supports of one pair fitted overhanging being placed symmetrically with respect to the centre line of the cavity, each slide tube being connected to the two supports of one pair. These support are connected to the slide wall of the cavity by an insulator located at their electrically free end. The accelerator structure composed of several structures placed end to end, the last one of which is fed by a high frequency field of adjustable amplitude and phase, enables a heavy ion linear accelerator to be built [fr

  4. Temperature fields occurring in dielectric capillaries for the transport of of ion beams

    International Nuclear Information System (INIS)

    Urbanovich, A.I.

    2012-01-01

    This paper presents the results of computing the temperature fields occurring in dielectric capillaries of glass for the transport of accelerated charged particles. It is shown that on the transport of ion beams with a power of several watts the capillary is heated intensively, whereas heat stresses may approach the lower bound associated with a real strength of glass. (authors)

  5. RF power generation and coupling measurements for the dielectric wakefield step-up transformer

    International Nuclear Information System (INIS)

    Conde, M. E.

    1998-01-01

    The dielectric wakefield transformer (DWT) is one route to practical high energy wakefield-based accelerators. Progress has been made in a number of areas relevant to the demonstration of this device. In this article we describe recent bench measurements and beam experiments using 7.8 and 15.6 GHz structures and discuss some remaining technical challenges in the development of the DWT

  6. A simple method for reducing inevitable dielectric loss in high-permittivity dielectric elastomers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Mazurek, Piotr Stanislaw

    2016-01-01

    elastomer matrix, with high dielectric permittivity and a low Young's modulus, aligned with no loss of mechanical stability, was prepared through the use of commercially available chloropropyl-functional silicone oil mixed into a tough commercial liquid silicone rubber silicone elastomer. The addition...... also decreased the dielectric losses of an elastomer containing dielectric permittivity-enhancing TiO2 fillers. Commercially available chloropropyl-functional silicone oil thus constitutes a facile method for improved silicone DEs, with very low dielectric losses.......Commercial viability of dielectric elastomers (DEs) is currently limited by a few obstacles, including high driving voltages (in the kV range). Driving voltage can be lowered by either decreasing the Young's modulus or increasing the dielectric permittivity of silicone elastomers, or a combination...

  7. Dielectrics in electric fields

    CERN Document Server

    Raju, Gorur G

    2003-01-01

    Discover nontraditional applications of dielectric studies in this exceptionally crafted field reference or text for seniors and graduate students in power engineering tracks. This text contains more than 800 display equations and discusses polarization phenomena in dielectrics, the complex dielectric constant in an alternating electric field, dielectric relaxation and interfacial polarization, the measurement of absorption and desorption currents in time domains, and high field conduction phenomena. Dielectrics in Electric Fields is an interdisciplinary reference and text for professionals and students in electrical and electronics, chemical, biochemical, and environmental engineering; physical, surface, and colloid chemistry; materials science; and chemical physics.

  8. NPPs Secondary Circuit Piping Wall-Thinning Management in China

    International Nuclear Information System (INIS)

    Zhong Zhimin; Li Jinsong; Zheng Hui

    2012-01-01

    Since 1980s, secondary circuit piping wall-thinning incidents happened in nuclear power plants (NPPs) worldwide. Particularly Surry 2 and Mihama 3 accidents resulted from flow-accelerated corrosion (FAC), unplanned outage, huge fatalities and economic loss pushed whole industry to pay more attention on the wall-thinning problem.

  9. Attosecond control of electron beams at dielectric and absorbing membranes

    Science.gov (United States)

    Morimoto, Yuya; Baum, Peter

    2018-03-01

    Ultrashort electron pulses are crucial for time-resolved electron diffraction and microscopy of the fundamental light-matter interaction. In this work, we study experimentally and theoretically the generation and characterization of attosecond electron pulses by optical-field-driven compression and streaking at dielectric or absorbing interaction elements. The achievable acceleration and deflection gradient depends on the laser-electron angle, the laser's electric and magnetic field directions, and the foil orientation. Electric and magnetic fields have similar contributions to the final effect and both need to be considered. Experiments and theory agree well and reveal the optimum conditions for highly efficient, velocity-matched electron-field interactions in the longitudinal or transverse direction. We find that metallic membranes are optimum for light-electron control at mid-infrared or terahertz wavelengths, but dielectric membranes are excellent in the visible and near-infrared regimes and are therefore ideal for the formation of attosecond electron pulses.

  10. Analysis of FFAG accelerators and the evolution of circular accelerators

    International Nuclear Information System (INIS)

    Laslett, J.

    1961-01-01

    After rapidly comparing circular machines with the linear accelerator and the reasons for the choice of an annular high energy and very high intensity accelerator, recent problems concerning accelerator theory are discussed, with emphasis on their physical character. The FFAG principle. The limit of the energy of FFAG cyclotron. The setting-up and interpreting of mean energy of focusing terms for a spiral FFAG synchrotron. The limiting amplitude stable near the non-linear resonance 2Q z = Q r , as well as the linear coupling resonance of Walkinshaw 2Q z = Q r . The crossed-beam accelerator. The 40 MeV electron model of MURA. Two other parts deal with linear and non-linear methods of injection and extraction using a variable disturbance applied to the magnetic field, as well as to collective effects. The interaction of the beam with the accelerating cavities and the walls. The modification of the phase oscillation equation. The influence of the beams' high frequency fields on the Nielsen longitudinal instability. (author) [fr

  11. Inductive dielectric analyzer

    International Nuclear Information System (INIS)

    Agranovich, Daniel; Popov, Ivan; Ben Ishai, Paul; Feldman, Yuri; Polygalov, Eugene

    2017-01-01

    One of the approaches to bypass the problem of electrode polarization in dielectric measurements is the free electrode method. The advantage of this technique is that, the probing electric field in the material is not supplied by contact electrodes, but rather by electromagnetic induction. We have designed an inductive dielectric analyzer based on a sensor comprising two concentric toroidal coils. In this work, we present an analytic derivation of the relationship between the impedance measured by the sensor and the complex dielectric permittivity of the sample. The obtained relationship was successfully employed to measure the dielectric permittivity and conductivity of various alcohols and aqueous salt solutions. (paper)

  12. Dielectric nanoresonators for light manipulation

    Science.gov (United States)

    Yang, Zhong-Jian; Jiang, Ruibin; Zhuo, Xiaolu; Xie, Ya-Ming; Wang, Jianfang; Lin, Hai-Qing

    2017-07-01

    Nanostructures made of dielectric materials with high or moderate refractive indexes can support strong electric and magnetic resonances in the optical region. They can therefore function as nanoresonators. In addition to plasmonic metal nanostructures that have been widely investigated, dielectric nanoresonators provide a new type of building blocks for realizing powerful and versatile nanoscale light manipulation. In contrast to plasmonic metal nanostructures, nanoresonators made of appropriate dielectric materials are low-cost, earth-abundant and have very small or even negligible light energy losses. As a result, they will find potential applications in a number of photonic devices, especially those that require low energy losses. In this review, we describe the recent progress on the experimental and theoretical studies of dielectric nanoresonators. We start from the basic theory of the electromagnetic responses of dielectric nanoresonators and their fabrication methods. The optical properties of individual dielectric nanoresonators are then elaborated, followed by the coupling behaviors between dielectric nanoresonators, between dielectric nanoresonators and substrates, and between dielectric nanoresonators and plasmonic metal nanostructures. The applications of dielectric nanoresonators are further described. Finally, the challenges and opportunities in this field are discussed.

  13. Propagation properties of dielectric-lined hollow cylindrical metallic waveguides for THz waves

    International Nuclear Information System (INIS)

    Huang Binke; Zhao Chongfeng

    2013-01-01

    For the rigorous analysis of the propagation properties of dielectric-lined hollow cylindrical metallic waveguides operating in the THz range of frequencies, the characteristic equation for propagation constants is derived from the electromagnetic field equations and the boundary conditions of the dielectric-lined waveguides. The propagation constant of the dominant hybrid HE 11 mode can be obtained by solving the characteristic equation with the improved Muller method. The classical relaxation-effect model for the conductivity is adopted to describe the frequency dispersive behavior of normal metals for the metallic waveguide wall. For a 1.8 mm bore diameter silver waveguide with the inner surface coated with a 17 μm-thick layer of polystyrene(PS) film, the transmission losses of HE 11 mode can be reduced to the level below 1 dB/m at 1.5-3.0 THz, and the dispersion is relatively small for HE 11 mode. In addition, with the PS film thickness increasing, the transmission losses of HE 11 mode increase first and then decrease for a 2.2 mm bore diameter silver waveguide at 2.5 THz, and the minimum loss can be achieved by adopting the optimum dielectric layer thickness. (authors)

  14. Radiation Characteristics Enhancement of Dielectric Resonator Antenna Using Solid/Discrete Dielectric Lenses

    Directory of Open Access Journals (Sweden)

    H. A. E. Malhat

    2015-02-01

    Full Text Available The radiation characteristics of the dielectric resonator antennas (DRA is enhanced using different types of solid and discrete dielectric lenses. One of these approaches is by loading the DRA with planar superstrate, spherical lens, or by discrete lens (transmitarray. The dimensions and dielectric constant of each lens are optimized to maximize the gain of the DRA. A comparison between the radiations characteristics of the DRA loaded with different lenses are introduced. The design of the dielectric transmitarray depends on optimizing the heights of the dielectric material of the unit cell. The optimized transmitarray achieves 7 dBi extra gain over the single DRA with preserving the circular polarization. The proposed antenna is suitable for various applications that need high gain and focused antenna beam.

  15. Inverse Free Electron Laser accelerator

    International Nuclear Information System (INIS)

    Fisher, A.; Gallardo, J.; van Steenbergen, A.; Sandweiss, J.

    1992-09-01

    The study of the INVERSE FREE ELECTRON LASER, as a potential mode of electron acceleration, is being pursued at Brookhaven National Laboratory. Recent studies have focussed on the development of a low energy, high gradient, multi stage linear accelerator. The elementary ingredients for the IFEL interaction are the 50 MeV Linac e - beam and the 10 11 Watt CO 2 laser beam of BNL's Accelerator Test Facility (ATF), Center for Accelerator Physics (CAP) and a wiggler. The latter element is designed as a fast excitation unit making use of alternating stacks of Vanadium Permendur (VaP) ferromagnetic laminations, periodically interspersed with conductive, nonmagnetic laminations, which act as eddy current induced field reflectors. Wiggler parameters and field distribution data will be presented for a prototype wiggler in a constant period and in a ∼ 1.5 %/cm tapered period configuration. The CO 2 laser beam will be transported through the IFEL interaction region by means of a low loss, dielectric coated, rectangular waveguide. Short waveguide test sections have been constructed and have been tested using a low power cw CO 2 laser. Preliminary results of guide attenuation and mode selectivity will be given, together with a discussion of the optical issues for the IFEL accelerator. The IFEL design is supported by the development and use of 1D and 3D simulation programs. The results of simulation computations, including also wiggler errors, for a single module accelerator and for a multi-module accelerator will be presented

  16. Reducing the asymmetry in coupled cavity of linear accelerator

    International Nuclear Information System (INIS)

    Wei Xianlin; Wu Congfeng

    2013-01-01

    Background: With the development of high energy physics, high performance of electron linear accelerator is required for large collider, FEL and high brightness synchrotron radiation light source. Structure asymmetry of single coupler destroys the symmetry of field distribution in coupled cavity, which reduces the quality of beam. Purpose: Optimize the asymmetry of field distribution in coupled cavity and improve the quality of beam. Methods: The simulation designs are made for single offset coupler, double symmetry coupler and the new coupler loaded by dielectric rods at X band by using CST microwave studio code. Results: The results show that the distribution of field in coupled cavity is better and all particles almost locate at the center of beam hole after beam passing through the coupler loaded by dielectric rods. The energy spread has also been significantly improved. Conclusions: The coupler loaded by dielectric rods can optimize the asymmetry of field distribution in coupled cavity and improve the quality of beam. (authors)

  17. Experimental and Numerical Investigation of Compact Dielectric Wakefield Accelerators

    Science.gov (United States)

    2016-03-01

    macroparticles. Additionally the laser is chosen to have a transverse rms spot size of σc = 0.8 mm and rms duration of σt = 1 ps. A solenoidal lens is...photocathode laser . . . . . . . . . . 24 3.3 Experimental realization of a linearly-ramped bunch with a multifrequency linac... laser . Our approach toward the development of a compact beam-driven accelerator consists of four main components depicted in Fig. 1. The production of

  18. Effect of Anode Dielectric Coating on Hall Thruster Operation

    International Nuclear Information System (INIS)

    Dorf, L.; Raitses, Y.; Fisch, N.J.; Semenov, V.

    2003-01-01

    An interesting phenomenon observed in the near-anode region of a Hall thruster is that the anode fall changes from positive to negative upon removal of the dielectric coating, which is produced on the anode surface during the normal course of Hall thruster operation. The anode fall might affect the thruster lifetime and acceleration efficiency. The effect of the anode coating on the anode fall is studied experimentally using both biased and emissive probes. Measurements of discharge current oscillations indicate that thruster operation is more stable with the coated anode

  19. Dielectric materials for electrical engineering

    CERN Document Server

    Martinez-Vega, Juan

    2013-01-01

    Part 1 is particularly concerned with physical properties, electrical ageing and modeling with topics such as the physics of charged dielectric materials, conduction mechanisms, dielectric relaxation, space charge, electric ageing and life end models and dielectric experimental characterization. Part 2 concerns some applications specific to dielectric materials: insulating oils for transformers, electrorheological fluids, electrolytic capacitors, ionic membranes, photovoltaic conversion, dielectric thermal control coatings for geostationary satellites, plastics recycling and piezoelectric poly

  20. Improved Dielectric Films For Capacitors

    Science.gov (United States)

    Yen, Shiao-Ping S.; Lewis, Carol R.; Cygan, Peter J.; Jow, T. Richard

    1994-01-01

    Dielectric films made from blends of some commercially available high-dielectric-constant cyanoresins with each other and with cellulose triacetate (CTA) have both high dielectric constants and high breakdown strengths. Dielectric constants as high as 16.2. Films used to produce high-energy-density capacitors.

  1. Stop Band Gap in Periodic Layers of Confined Atomic Vapor/Dielectric Medium

    International Nuclear Information System (INIS)

    Li Yuan-Yuan; Li Li; Lu Yi-Xin; Zhang Yan-Peng; Xu Ke-Wei

    2013-01-01

    A stop band gap is predicted in periodic layers of a confined atomic vapor/dielectric medium. Reflection and transmission profile of the layers over the band gap can be dramatically modified by the confined atoms and the number of layer periods. These gap and line features can be ascribed to the enhanced contribution of slow atoms induced by atom-wall collision, transient behavior of atom-light interaction and Fabry—Pérot effects in a thermal confined atomic system

  2. One-equation modeling and validation of dielectric barrier discharge plasma actuator thrust

    International Nuclear Information System (INIS)

    Yoon, Jae-San; Han, Jae-Hung

    2014-01-01

    Dielectric barrier discharge (DBD) plasma actuators with an asymmetric electrode configuration can generate a wall-bounded jet without mechanical moving parts, which require considerable modifications of existing aeronautical objects and which incur high maintenance costs. Despite this potential, one factor preventing the wider application of such actuators is the lack of a reliable actuator model. It is difficult to develop such a model because calculating the ion-electric field and fluid interaction consume a high amount calculation effort during the numerical analysis. Thus, the authors proposed a semi-empirical model which predicted the thrust of plasma actuators with a simple equation. It gave a numeric thrust value, and we implemented the value on a computational fluid dynamics (CFD) solver to describe the two-dimensional flow field induced by the actuator. However, the model had a narrow validation range, depending on the empirical formula, and it did not fully consider environment variables. This study presents an improved model by replacing the empirical formulae in the previous model with physical equations that take into account physical phenomena and environmental variables. During this process, additional operation parameters, such as pressure, temperature and ac waveforms, are newly taken to predict the thrust performance of the actuators with a wider range of existing parameters, the thickness of the dielectric barrier, the exposed electrode, the dielectric constant, the ac frequency and the voltage amplitude. Thrust prediction curves from the model are compared to those of earlier experimental results, showing that the average error is less than 5% for more than one hundred instances of data. As in the earlier work, the predicted thrust value is implemented on a CFD solver, and two-dimensional wall-jet velocity profiles induced by the actuator are compared to the previous experimental results. (paper)

  3. Nonlinear electroelastic deformations of dielectric elastomer composites: II - Non-Gaussian elastic dielectrics

    Science.gov (United States)

    Lefèvre, Victor; Lopez-Pamies, Oscar

    2017-02-01

    This paper presents an analytical framework to construct approximate homogenization solutions for the macroscopic elastic dielectric response - under finite deformations and finite electric fields - of dielectric elastomer composites with two-phase isotropic particulate microstructures. The central idea consists in employing the homogenization solution derived in Part I of this work for ideal elastic dielectric composites within the context of a nonlinear comparison medium method - this is derived as an extension of the comparison medium method of Lopez-Pamies et al. (2013) in nonlinear elastostatics to the coupled realm of nonlinear electroelastostatics - to generate in turn a corresponding solution for composite materials with non-ideal elastic dielectric constituents. Complementary to this analytical framework, a hybrid finite-element formulation to construct homogenization solutions numerically (in three dimensions) is also presented. The proposed analytical framework is utilized to work out a general approximate homogenization solution for non-Gaussian dielectric elastomers filled with nonlinear elastic dielectric particles that may exhibit polarization saturation. The solution applies to arbitrary (non-percolative) isotropic distributions of filler particles. By construction, it is exact in the limit of small deformations and moderate electric fields. For finite deformations and finite electric fields, its accuracy is demonstrated by means of direct comparisons with finite-element solutions. Aimed at gaining physical insight into the extreme enhancement in electrostriction properties displayed by emerging dielectric elastomer composites, various cases wherein the filler particles are of poly- and mono-disperse sizes and exhibit different types of elastic dielectric behavior are discussed in detail. Contrary to an initial conjecture in the literature, it is found (inter alia) that the isotropic addition of a small volume fraction of stiff (semi

  4. A water-filled radio frequency accelerating cavity

    International Nuclear Information System (INIS)

    Faehl, R.J.; Keinigs, R.K.; Pogue, E.W.

    1998-01-01

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The objective of this project was to study water-filled resonant cavities as a high-energy density source to drive high-current accelerator configurations. Basic considerations lead to the expectation that a dielectric-filled cavity should be able to store up to e/e o as much energy as a vacuum one with the same dimensions and thus be capable of accelerating a proportionately larger amount of charge before cavity depletion occurs. During this project, we confirmed that water-filled cavities with e/e o = 60-80 did indeed behave with the expected characteristics, in terms of resonant TM modes and cavity Q. We accomplished this result with numerical cavity eigenvalue codes; fully electromagnetic, two-dimensional, particle-in-cell codes; and, most significantly, with scaled experiments performed in water-filled aluminum cavities. The low-power experiments showed excellent agreement with the numerical results. Simulations of the high-field, high-current mode of operation indicated that charged-particle loss on the dielectric windows, which separate the cavity from the beamline, must be carefully controlled to avoid significant distortion of the axial fields

  5. Ceramic-polymer nanocomposites with increased dielectric permittivity and low dielectric loss

    International Nuclear Information System (INIS)

    Bhardwaj, Sumit; Paul, Joginder; Raina, K. K.; Thakur, N. S.; Kumar, Ravi

    2014-01-01

    The use of lead free materials in device fabrication is very essential from environmental point of view. We have synthesized the lead free ferroelectric polymer nanocomposite films with increased dielectric properties. Lead free bismuth titanate has been used as active ceramic nanofillers having crystallite size 24nm and PVDF as the polymer matrix. Ferroelectric β-phase of the polymer composite films was confirmed by X-ray diffraction pattern. Mapping data confirms the homogeneous dispersion of ceramic particles into the polymer matrix. Frequency dependent dielectric constant increases up to 43.4 at 100Hz, whereas dielectric loss decreases with 7 wt% bismuth titanate loading. This high dielectric constant lead free ferroelectric polymer films can be used for energy density applications

  6. Performance of the Argonne Wakefield Accelerator Facility and initial experimental results

    International Nuclear Information System (INIS)

    Gai, W.; Conde, M.; Cox, G.; Konecny, R.; Power, J.; Schoessow, P.; Simpson, J.; Barov, N.

    1996-01-01

    The Argonne Wakefield Accelerator facility has begun its experimental program. It is designed to address advanced acceleration research requiring very short, intense electron bunches. It incorporates two photocathode based electron sources. One produces up to 100 nC, multi-kiloamp 'drive' bunches which are used to excite wakefields in dielectric loaded structures and in plasma. The second source produces much lower intensity 'witness' pulses which are used to probe the fields produced by the drive. The drive and witness pulses can be precisely timed as well as laterally positioned with respect to each other. This paper discusses commissioning, initial experiments, and outline plans for a proposed 1 GeV demonstration accelerator

  7. Accelerated and Improved Differentiation of Retinal Organoids from Pluripotent Stem Cells in Rotating-Wall Vessel Bioreactors

    Directory of Open Access Journals (Sweden)

    Tyler DiStefano

    2018-01-01

    Full Text Available Pluripotent stem cells can be differentiated into 3D retinal organoids, with major cell types self-patterning into a polarized, laminated architecture. In static cultures, organoid development may be hindered by limitations in diffusion of oxygen and nutrients. Herein, we report a bioprocess using rotating-wall vessel (RWV bioreactors to culture retinal organoids derived from mouse pluripotent stem cells. Organoids in RWV demonstrate enhanced proliferation, with well-defined morphology and improved differentiation of neurons including ganglion cells and S-cone photoreceptors. Furthermore, RWV organoids at day 25 (D25 reveal similar maturation and transcriptome profile as those at D32 in static culture, closely recapitulating spatiotemporal development of postnatal day 6 mouse retina in vivo. Interestingly, however, retinal organoids do not differentiate further under any in vitro condition tested here, suggesting additional requirements for functional maturation. Our studies demonstrate that bioreactors can accelerate and improve organoid growth and differentiation for modeling retinal disease and evaluation of therapies.

  8. Initial results of the new high intensity electron gun at the Argonne Wakefield Accelerator

    International Nuclear Information System (INIS)

    Conde, M. E.; Gai, W.; Konecny, R.; Power, J. G.; Schoessow, P.; Sun, X.

    2000-01-01

    The authors report on the status of the new short bunch, high intensity electron gun at the Argonne Wakefield Accelerator. The 1-1/2 cell L-band photocathode RF gun is expected to produce 10--100 nC bunches with 2--5 ps rms pulse length and normalized emittance less than 100 mm mrad. The beam energy at the exit of the gun cavity will be in the range 7.5--10 MeV. A standing-wave linac structure operating at the same frequency (1.3 GHz) will increase the beam energy to about 15 MeV. This beam will be used in wakefield acceleration experiments with dielectric loaded structures. These travelling-wave dielectric loaded structures, operating at 7.8 and 15.6 GHz, will be excited by the propagation of single bunches or by trains of up to 32 electron bunches

  9. Cell wall assembly and intracellular trafficking in plant cells are directly affected by changes in the magnitude of gravitational acceleration.

    Directory of Open Access Journals (Sweden)

    Youssef Chebli

    Full Text Available Plants are able to sense the magnitude and direction of gravity. This capacity is thought to reside in selected cell types within the plant body that are equipped with specialized organelles called statoliths. However, most plant cells do not possess statoliths, yet they respond to changes in gravitational acceleration. To understand the effect of gravity on the metabolism and cellular functioning of non-specialized plant cells, we investigated a rapidly growing plant cell devoid of known statoliths and without gravitropic behavior, the pollen tube. The effects of hyper-gravity and omnidirectional exposure to gravity on intracellular trafficking and on cell wall assembly were assessed in Camellia pollen tubes, a model system with highly reproducible growth behavior in vitro. Using an epi-fluorescence microscope mounted on the Large Diameter Centrifuge at the European Space Agency, we were able to demonstrate that vesicular trafficking is reduced under hyper-gravity conditions. Immuno-cytochemistry confirmed that both in hyper and omnidirectional gravity conditions, the characteristic spatial profiles of cellulose and callose distribution in the pollen tube wall were altered, in accordance with a dose-dependent effect on pollen tube diameter. Our findings suggest that in response to gravity induced stress, the pollen tube responds by modifying cell wall assembly to compensate for the altered mechanical load. The effect was reversible within few minutes demonstrating that the pollen tube is able to quickly adapt to changing stress conditions.

  10. Fabrication of Nonvolatile Memory Effects in High-k Dielectric Thin Films Using Electron Irradiation

    International Nuclear Information System (INIS)

    Park, Chanrock; Cho, Daehee; Kim, Jeongeun; Hwang, Jinha

    2010-01-01

    Electron Irradiation can be applied towards nano-floating gate memories which are recognized as one of the next-generation nonvolatile memory semiconductors. NFGMs can overcome the preexisting limitations encountered in Dynamic Random Access Memories and Flash memories with the excellent advantages, i. e. high-density information storage, high response speed, high compactness, etc. The traditional nano-floating gate memories are fabricated through multi-layered nano structures of the dissimilar materials where the charge-trapping portions are sandwiched into the high-k dielectrics. However, this work reports the unique nonvolatile responses in single-layered high-k dielectric thin films if irradiated with highly accelerated electron beams. The implications of the electron irradiation will be discussed towards high-performance nano-floating gate memories

  11. Dielectric effect on electric fields in the vicinity of the metal–vacuum–dielectric junction

    International Nuclear Information System (INIS)

    Chung, M.S.; Mayer, A.; Miskovsky, N.M.; Weiss, B.L.; Cutler, P.H.

    2013-01-01

    The dielectric effect was theoretically investigated in order to describe the electric field in the vicinity of a junction of a metal, dielectric, and vacuum. The assumption of two-dimensional symmetry of the junction leads to a simple analytic form and to a systematic numerical calculation for the field. The electric field obtained for the triple junction was found to be enhanced or reduced according to a certain criterion determined by the contact angles and dielectric constant. Further numerical calculations of the dielectric effect show that an electric field can experience a larger enhancement or reduction for a quadruple junction than that achieved for the triple junction. It was also found that even though it changes slowly in comparison with the shape effect, the dielectric effect was noticeably large over the entire range of the shape change. - Highlights: ► This work explains how a very strong electric field can be produced due to the dielectric in the vicinity of metal–dielectric contact. ► This work deals with configurations which enhance electric fields using the dielectric effect. The configuration is a type of junction at which metal, vacuum and dielectric meet. ► This work suggests the criterion to determine whether field enhancement occurs or not in the triple junction of metal, vacuum and dielectric. ► This work suggests that a quadruple junction is more effective in enhancing the electric field than a triple junction. The quadruple junction is formed by an additional vacuum portion to the triple junction. ► This work suggests that a triple junction can be a breakthrough candidate for a cold electron source

  12. Interconnect Between a Waveguide and a Dielectric Waveguide Comprising an Impedance Matched Dielectric Lens

    Science.gov (United States)

    Decrossas, Emmanuel (Inventor); Chattopadhyay, Goutam (Inventor); Chahat, Nacer (Inventor); Tang, Adrian J. (Inventor)

    2016-01-01

    A lens for interconnecting a metallic waveguide with a dielectric waveguide is provided. The lens may be coupled a metallic waveguide and a dielectric waveguide, and minimize a signal loss between the metallic waveguide and the dielectric waveguide.

  13. New initiatives for producing high current electron accelerators

    International Nuclear Information System (INIS)

    Faehl, R.J.; Keinigs, R.K.; Pogue, E.W.

    1996-01-01

    New classes of compact electron accelerators able to deliver multi-kiloamperes of pulsed 10-50 MeV electron beams are being studied. One class is based upon rf linac technology with dielectric-filled cavities. For materials with ε/ε o >>1, the greatly increased energy storage permits high current operation. The second type is a high energy injected betatron. Circulating current limits scale as Β 2 γ 3

  14. Dependences of the van der Waals atom-wall interaction on atomic and material properties

    International Nuclear Information System (INIS)

    Caride, A.O.; Klimchitskaya, G.L.; Mostepanenko, V.M.; Zanette, S.I.

    2005-01-01

    The 1%-accurate calculations of the van der Waals interaction between an atom and a cavity wall are performed in the separation region from 3 nm to 150 nm. The cases of metastable He * and Na atoms near metal, semiconductor, and dielectric walls are considered. Different approximations to the description of wall material and atomic dynamic polarizability are carefully compared. The smooth transition to the Casimir-Polder interaction is verified. It is shown that to obtain accurate results for the atom-wall van der Waals interaction at short separations with an error less than 1% one should use the complete optical-tabulated data for the complex refractive index of the wall material and the accurate dynamic polarizability of an atom. The obtained results may be useful for the theoretical interpretation of recent experiments on quantum reflection and Bose-Einstein condensation of ultracold atoms on or near surfaces of different kinds

  15. Optimal Super Dielectric Material

    Science.gov (United States)

    2015-09-01

    plate capacitor will reduce the net field to an unprecedented extent. This family of materials can form materials with dielectric values orders of... Capacitor -Increase Area (A)............8 b. Multi-layer Ceramic Capacitor -Decrease Thickness (d) .......10 c. Super Dielectric Material-Increase...circuit modeling, from [44], and B) SDM capacitor charge and discharge ...................................................22 Figure 15. Dielectric

  16. Clustering Of Left Ventricular Wall Motion Patterns

    Science.gov (United States)

    Bjelogrlic, Z.; Jakopin, J.; Gyergyek, L.

    1982-11-01

    A method for detection of wall regions with similar motion was presented. A model based on local direction information was used to measure the left ventricular wall motion from cineangiographic sequence. Three time functions were used to define segmental motion patterns: distance of a ventricular contour segment from the mean contour, the velocity of a segment and its acceleration. Motion patterns were clustered by the UPGMA algorithm and by an algorithm based on K-nearest neighboor classification rule.

  17. Development of a dielectric ceramic based on diatomite-titania part two: dielectric properties characterization

    Directory of Open Access Journals (Sweden)

    Medeiros Jamilson Pinto

    1998-01-01

    Full Text Available Dielectric properties of sintered diatomite-titania ceramics are presented. Specific capacitance, dissipation factor, quality factor and dielectric constant were determined as a function of sintering temperature, titania content and frequency; the temperature coefficient of capacitance was measured as a function of frequency. Besides leakage current, the dependence of the insulation resistance and the dielectric strength on the applied dc voltage were studied. The results show that diatomite-titania compositions can be used as an alternative dielectric.

  18. Piezoelectric and dielectric characterization of corona and contact poled PZT-epoxy-MWCNT bulk composites

    Science.gov (United States)

    Banerjee, S.; Cook-Chennault, K. A.; Du, W.; Sundar, U.; Halim, H.; Tang, A.

    2016-11-01

    Three-phase lead zirconate titanate (PZT, PbZr0.52Ti0.48O3)-epoxy-multi-walled carbon nanotube (MWCNT) bulk composites were prepared, where the volume fraction of PZT was held constant at 30%, while the volume fraction of the MWCNTs was varied from 1.0%-10%. The samples were poled using either a parallel plate contact or contactless (corona) poling technique. The piezoelectric strain coefficient (d33), dielectric constant (ɛ), and dielectric loss tangent (tan δ) of the samples were measured at 110 Hz, and compared as a function of poling technique and volume fraction of MWCNTs. The highest values for dielectric constant and piezoelectric strain coefficients were 465.82 and 18.87 pC/N for MWCNT volume fractions of 10% and 6%, respectively. These values were obtained for samples that were poled using the corona contactless method. The impedance and dielectric spectra of the composites were recorded over a frequency range of 100 Hz-20 MHz. The impedance values observed for parallel-plate contact poled samples are higher than that of corona poled composites. The fractured surface morphology and distribution of the PZT particles and MWCNTs were observed with the aid of electron dispersion spectroscopy and a scanning electron microscope. The surface morphology of the MWCNTs was observed with the aid of a field emission transmission electron microscope.

  19. Performance of the Argonne Wakefield Accelerator facility and initial experimental results

    International Nuclear Information System (INIS)

    Gai, W.; Conde, M.; Cox, G.; Konecny, R.; Power, J.; Schoessow, P.; Simpson, J.; Barov, N.

    1996-01-01

    The Argonne Wakefield Accelerator (AWA) facility has begun its experimental program. This unique facility is designed to address advanced acceleration research which requires very short, intense electron bunches. The facility incorporates two photo-cathode based electron sources. One produces up to 100 nC, multi-kiloamp 'drive' bunches which are used to excite wakefields in dielectric loaded structures and in plasma. The second source produces much lower intensity 'witness' pulses which are used to probe the fields produced by the drive. The drive and witness pulses can be precisely timed as well as laterally positioned with respect to each other. We discuss commissioning, initial experiments, and outline plans for a proposed 1 GeV demonstration accelerator. (author)

  20. High dielectric permittivity and improved mechanical and thermal properties of poly(vinylidene fluoride) composites with low carbon nanotube content: effect of composite processing on phase behavior and dielectric properties.

    Science.gov (United States)

    Kumar, G Sudheer; Vishnupriya, D; Chary, K Suresh; Patro, T Umasankar

    2016-09-23

    The composite processing technique and nanofiller concentration and its functionalization significantly alter the properties of polymer nanocomposites. To realize this, multi-walled carbon nanotubes (CNT) were dispersed in a poly(vinylidene fluoride) (PVDF) matrix at carefully selected CNT concentrations by two illustrious methods, such as solution-cast and melt-mixing. Notwithstanding the processing method, CNTs induced predominantly the γ-phase in PVDF, instead of the commonly obtained β-phase upon nanofiller incorporation, and imparted significant improvements in dielectric properties. Acid-treatment of CNT improved its dispersion and interfacial adhesion significantly with PVDF, and induced a higher γ-phase content and better dielectric properties in PVDF as compared to pristine CNT. Further, the γ-phase content was found to be higher in solution-cast composites than that in melt-mixed counterparts, most likely due to solvent-induced crystallization in a controlled environment and slow solvent evaporation in the former case. However, interestingly, the melt-mixed composites showed a significantly higher dielectric constant at the onset of the CNT networked-structure as compared to the solution-cast composites. This suggests the possible role of CNT breakage during melt-mixing, which might lead to higher space-charge polarization at the polymer-CNT interface, and in turn an increased number of pseudo-microcapacitors in these composites than the solution-cast counterparts. Notably, PVDF with 0.13 vol% (volume fraction, f c  = 0.0013) of acid-treated CNTs, prepared by melt-mixing, displayed the relative permittivity of ∼217 and capacitance of ∼5430 pF, loss tangent of ∼0.4 at 1 kHz and an unprecedented figure of merit of ∼10(5). We suggest a simple hypothesis for the γ-phase formation and evolution of the high dielectric constant in these composites. Further, the high-dielectric composite film showed marked improvements in mechanical and thermal

  1. 5 MeV 300 kW electron accelerator project

    International Nuclear Information System (INIS)

    Auslender, V.L.; Cheskidov, V.G.; Gornakov, I.V.

    2004-01-01

    The paper presents a project of a high power linear accelerator for industrial applications. The accelerator has a modular structure and consists of the chain of accelerating cavities connected by the axis-located coupling cavities with coupling slots in the common walls. Main parameters of the accelerator are: operating frequency of 176 MHz, electron energy of up to 5 MeV, average beam power of 300 kW. The required RF pulse power can be supplied by the TH628 diacrode

  2. Acceleration of particles in plasmas

    CERN Multimedia

    CERN. Geneva

    2007-01-01

    The accelerating fields in radio-frequency accelerators are limited to roughly 100 MV/m due to material breakdown which occurs on the walls of the structure. In contrast, a plasma, being already ionized, can support electric fields in excess of 100 GV/m. Such high accelerating gradients hold the promise of compact particle accelerators. Plasma acceleration has been an emerging and fast growing field of research in the past two decades. In this series of lectures, we will review the principles of plasma acceleration. We will see how relativistic plasma waves can be excited using an ultra-intense laser or using a particle beam. We will see how these plasma waves can be used to accelerate electrons to high energy in short distances. Throughout the lectures, we will also review recent experimental results. Current laser-plasma experiments throughout the world have shown that monoenergetic electron beams from 100 MeV to 1 GeV can be obtained in distances ranging from the millimetre to the centimetre. Experiments a...

  3. Dielectric Behavior of Low Microwave Loss Unit Cell for All Dielectric Metamaterial

    Directory of Open Access Journals (Sweden)

    Tianhuan Luo

    2015-01-01

    Full Text Available With a deep study of the metamaterial, its unit cells have been widely extended from metals to dielectrics. The dielectric based unit cells attract much attention because of the advantage of easy preparation, tunability, and higher frequency response, and so forth. Using the conventional solid state method, we prepared a kind of incipient ferroelectrics (calcium titanate, CaTiO3 with higher microwave permittivity and lower loss, which can be successfully used to construct metamaterials. The temperature and frequency dependence of dielectric constant are also measured under different sintering temperatures. The dielectric spectra showed a slight permittivity decrease with the increase of temperature and exhibited a loss of 0.0005, combined with a higher microwave dielectric constant of ~167 and quality factor Q of 2049. Therefore, CaTiO3 is a kind of versatile and potential metamaterial unit cell. The permittivity of CaTiO3 at higher microwave frequency was also examined in the rectangular waveguide and we got the permittivity of 165, creating a new method to test permittivity at higher microwave frequency.

  4. Influence of grid resolution in fluid-model simulation of nanosecond dielectric barrier discharge plasma actuator

    Science.gov (United States)

    Hua, Weizhuo; Fukagata, Koji

    2018-04-01

    Two-dimensional numerical simulation of a surface dielectric barrier discharge (SDBD) plasma actuator, driven by a nanosecond voltage pulse, is conducted. A special focus is laid upon the influence of grid resolution on the computational result. It is found that the computational result is not very sensitive to the streamwise grid spacing, whereas the wall-normal grid spacing has a critical influence. In particular, the computed propagation velocity changes discontinuously around the wall-normal grid spacing about 2 μm due to a qualitative change of discharge structure. The present result suggests that a computational grid finer than that was used in most of previous studies is required to correctly capture the structure and dynamics of streamer: when a positive nanosecond voltage pulse is applied to the upper electrode, a streamer forms in the vicinity of upper electrode and propagates along the dielectric surface with a maximum propagation velocity of 2 × 108 cm/s, and a gap with low electron and ion density (i.e., plasma sheath) exists between the streamer and dielectric surface. Difference between the results obtained using the finer and the coarser grid is discussed in detail in terms of the electron transport at a position near the surface. When the finer grid is used, the low electron density near the surface is caused by the absence of ionization avalanche: in that region, the electrons generated by ionization is compensated by drift-diffusion flux. In contrast, when the coarser grid is used, underestimated drift-diffusion flux cannot compensate the electrons generated by ionization, and it leads to an incorrect increase of electron density.

  5. Silicone elastomers with high dielectric permittivity and high dielectric breakdown strength based on tunable functionalized copolymers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Daugaard, Anders Egede

    2015-01-01

    system, with respect to functionalization, is achieved. It is investigated how the different functionalization variables affect essential DE properties, including dielectric permittivity, dielectric loss, elastic modulus and dielectric breakdown strength, and the optimal degree of chemical......%) was obtained without compromising other vital DE properties such as elastic modulus, gel fraction, dielectric and viscous loss and electrical breakdown strength....

  6. Electric-field control of magnetic domain-wall velocity in ultrathin cobalt with perpendicular magnetization.

    Science.gov (United States)

    Chiba, D; Kawaguchi, M; Fukami, S; Ishiwata, N; Shimamura, K; Kobayashi, K; Ono, T

    2012-06-06

    Controlling the displacement of a magnetic domain wall is potentially useful for information processing in magnetic non-volatile memories and logic devices. A magnetic domain wall can be moved by applying an external magnetic field and/or electric current, and its velocity depends on their magnitudes. Here we show that the applying an electric field can change the velocity of a magnetic domain wall significantly. A field-effect device, consisting of a top-gate electrode, a dielectric insulator layer, and a wire-shaped ferromagnetic Co/Pt thin layer with perpendicular anisotropy, was used to observe it in a finite magnetic field. We found that the application of the electric fields in the range of ± 2-3 MV cm(-1) can change the magnetic domain wall velocity in its creep regime (10(6)-10(3) m s(-1)) by more than an order of magnitude. This significant change is due to electrical modulation of the energy barrier for the magnetic domain wall motion.

  7. Advanced Accelerator Development Strategy Report: DOE Advanced Accelerator Concepts Research Roadmap Workshop

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2016-02-03

    Over a full two day period, February 2–3, 2016, the Office of High Energy Physics convened a workshop in Gaithersburg, MD to seek community input on development of an Advanced Accelerator Concepts (AAC) research roadmap. The workshop was in response to a recommendation by the HEPAP Accelerator R&D Subpanel [1] [2] to “convene the university and laboratory proponents of advanced acceleration concepts to develop R&D roadmaps with a series of milestones and common down selection criteria towards the goal for constructing a multi-TeV e+e– collider” (the charge to the workshop can be found in Appendix A). During the workshop, proponents of laser-driven plasma wakefield acceleration (LWFA), particle-beam-driven plasma wakefield acceleration (PWFA), and dielectric wakefield acceleration (DWFA), along with a limited number of invited university and laboratory experts, presented and critically discussed individual concept roadmaps. The roadmap workshop was preceded by several preparatory workshops. The first day of the workshop featured presentation of three initial individual roadmaps with ample time for discussion. The individual roadmaps covered a time period extending until roughly 2040, with the end date assumed to be roughly appropriate for initial operation of a multi-TeV e+e– collider. The second day of the workshop comprised talks on synergies between the roadmaps and with global efforts, potential early applications, diagnostics needs, simulation needs, and beam issues and challenges related to a collider. During the last half of the day the roadmaps were revisited but with emphasis on the next five to ten years (as specifically requested in the charge) and on common challenges. The workshop concluded with critical and unanimous endorsement of the individual roadmaps and an extended discussion on the characteristics of the common challenges. (For the agenda and list of participants see Appendix B.)

  8. The Experimental Stand for Research of Wakefield Method of Charged Particles Acceleration

    International Nuclear Information System (INIS)

    Kiselev, V.A.; Linnik, A.F.; Onishchenko, I.N.; Onishchenko, N.I.; Sotnikov, G.V.; Uskov, V.V.

    2006-01-01

    The experimental installation and diagnostic equipment with motivation to use for various researches of wakefield method of charged particles acceleration both in plasma and in dielectric structure has been described. The main parameters of a sequence of short relativistic electron bunch and values of physical characteristics of slow-down structures have been presented

  9. Silicone elastomers with high dielectric permittivity and high dielectric breakdown strength based on dipolar copolymers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Daugaard, Anders Egede

    2014-01-01

    Dielectric elastomers (DES) are a promising new transducer technology, but high driving voltages limit their current commercial potential. One method used to lower driving voltage is to increase dielectric permittivity of the elastomer. A novel silicone elastomer system with high dielectric...

  10. Many-particle hydrodynamic interactions in parallel-wall geometry: Cartesian-representation method

    International Nuclear Information System (INIS)

    Blawzdziewicz, J.; Wajnryb, E.; Bhattacharya, S.

    2005-01-01

    This talk will describe the results of our theoretical and numerical studies of hydrodynamic interactions in a suspension of spherical particles confined between two parallel planar walls, under creeping-flow conditions. We propose an efficient algorithm for evaluating many-particle friction matrix in this system-no Stokesian-dynamics algorithm of this kind has been available so far. Our approach involves expanding the fluid velocity field in the wall-bounded suspension into spherical and Cartesian fundamental sets of Stokes flows. The spherical set is used to describe the interaction of the fluid with the particles and the Cartesian set to describe the interaction with the walls. At the core of our method are transformation relations between the spherical and Cartesian fundamental sets. Using the transformation formulas, we derive a system of linear equations for the force multipoles induced on the particle surfaces; the coefficients in these equations are given in terms of lateral Fourier integrals corresponding to the directions parallel to the walls. The force-multipole equations have been implemented in a numerical algorithm for the evaluation of the multiparticle friction matrix in the wall-bounded system. The algorithm involves subtraction of the particle-wall and particle-particle lubrication contributions to accelerate the convergence of the results with the spherical-harmonics order, and a subtraction of the single-wall contributions to accelerate the convergence of the Fourier integrals. (author)

  11. Super Dielectric Materials.

    Science.gov (United States)

    Fromille, Samuel; Phillips, Jonathan

    2014-12-22

    Evidence is provided here that a class of materials with dielectric constants greater than 10⁵ at low frequency (dielectric materials (SDM), can be generated readily from common, inexpensive materials. Specifically it is demonstrated that high surface area alumina powders, loaded to the incipient wetness point with a solution of boric acid dissolved in water, have dielectric constants, near 0 Hz, greater than 4 × 10⁸ in all cases, a remarkable increase over the best dielectric constants previously measured for energy storage capabilities, ca. 1 × 10⁴. It is postulated that any porous, electrically insulating material (e.g., high surface area powders of silica, titania, etc. ), filled with a liquid containing a high concentration of ionic species will potentially be an SDM. Capacitors created with the first generated SDM dielectrics (alumina with boric acid solution), herein called New Paradigm Super (NPS) capacitors display typical electrostatic capacitive behavior, such as increasing capacitance with decreasing thickness, and can be cycled, but are limited to a maximum effective operating voltage of about 0.8 V. A simple theory is presented: Water containing relatively high concentrations of dissolved ions saturates all, or virtually all, the pores (average diameter 500 Å) of the alumina. In an applied field the positive ionic species migrate to the cathode end, and the negative ions to the anode end of each drop. This creates giant dipoles with high charge, hence leading to high dielectric constant behavior. At about 0.8 V, water begins to break down, creating enough ionic species to "short" the individual water droplets. Potentially NPS capacitor stacks can surpass "supercapacitors" in volumetric energy density.

  12. Magneto-optical study of domain wall dynamics and giant Barkhausen jump in magnetic microwires

    International Nuclear Information System (INIS)

    Chizhik, A.; Zhukov, A.; Blanco, J.M.; Gonzalez, J.

    2012-01-01

    Investigation of surface domain walls motion in Co-rich magnetic microwires has been performed in circular and axial magnetic fields. The dc axial magnetic field acceleration of the domain wall motion related to the influence of the axial field on the structure of the moving domain wall has been discovered. Pulsed axial magnetic field induced unidirectional motion of surface domain wall also has been found.

  13. Contemporary dielectric materials

    CERN Document Server

    Saravanan, R

    2016-01-01

    This book deals with experimental results of the physical characterization of several important, dielectric materials of great current interest. The experimental tools used for the analysis of these materials include X-ray diffraction, dielectric measurements, magnetic measurements using a vibrating sample magnetometer, optical measurements using a UV-Visible spectrometer etc.

  14. Excitation of THz hybrid modes in an elliptical dielectric rod waveguide with a cold collisionless unmagnetized plasma column by an annular electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Rahmani, Z., E-mail: z.rahmani@kashanu.ac.ir; Safari, S. [Department of Laser and Photonics, Faculty of Physics, University of Kashan, Kashan, Islamic Republic of Iran (Iran, Islamic Republic of); Heidari-Semiromi, E. [Department of Condense Matter, Faculty of Physics, University of Kashan, Kashan, Islamic Republic of Iran (Iran, Islamic Republic of)

    2016-06-15

    The dispersion relation of electromagnetic waves propagating in an elliptical plasma waveguide with a cold collisionless unmagnetized plasma column and a dielectric rod is studied analytically. The frequency spectrum of the hybrid waves and the growth rate for excitation of the waves by a thin annular relativistic elliptical electron beam (TAREEB) is obtained. The effects of relative permittivity constant of dielectric rod, geometrical dimensions, plasma frequency, accelerating voltage, and current density of TAREEB on the growth rate and frequency spectra of the waveguide will be investigated.

  15. Special radiation protection aspects of medical accelerators

    CERN Document Server

    Silari, Marco

    2001-01-01

    Radiation protection aspects relevant to medical accelerators are discussed. An overview is first given of general safety requirements. Next. shielding and labyrinth design are discussed in some detail for the various types of accelerators, devoting more attention to hadron machines as they are far less conventional than electron linear accelerators. Some specific aspects related to patient protection are also addressed. Finally, induced radioactivity in accelerator components and shielding walls is briefly discussed. Three classes of machines are considered: (1) medical electron linacs for 'conventional' radiation therapy. (2) low energy cyclotrons for production of radionuclides mainly for medical diagnostics and (3) medium energy cyclotrons and synchrotrons for advanced radiation therapy with protons or light ion beams (hadron therapy). (51 refs).

  16. The Effects of Single-Wall Carbon Nanotubes on the Shear Piezoelectricity of Biopolymers

    Science.gov (United States)

    Lovell, Conrad; Fitz-Gerald, James M.; Harrison, Joycelyn S.; Park, Cheol

    2008-01-01

    Shear piezoelectricity was investigated in a series of composites consisting of increased loadings of single-wall carbon nanotubes (SWCNTs) in poly (gamma-benzyl-L-glutamate), or PBLG. The effects of the SWCNTs on this material property in PBLG will be discussed. Their influence on the morphology of the polymer (degree of orientation and crystallinity), and electrical and dielectric properties of the composite will be reported

  17. Finite-size resonance dielectric cylinder in a rectangular waveguide

    International Nuclear Information System (INIS)

    Chuprina, V.N.; Khizhnyak, N.A.

    1988-01-01

    The problem on resonance spread of an electromagnetic wave by a dielectric circular cylinder of finite size in a rectangular waveguide is solved by a numerical-analytical method. The cylinder axes are parallel. The cylinder can be used as a resonance tuning element in accelerating SHF-sections. Problems on cutting off linear algebraic equation systems, to which relations of macroscopic electrodynamics in the integral differential form written for the concrete problem considered here are reduced by analytical transformations, are investigated in the stage of numerical analysis. Theoretical dependences of the insertion of the voltage standing wave coefficient on the generator wave length calculated for different values of problem parameters are constracted

  18. Super Dielectric Materials

    Directory of Open Access Journals (Sweden)

    Samuel Fromille

    2014-12-01

    Full Text Available Evidence is provided here that a class of materials with dielectric constants greater than 105 at low frequency (<10−2 Hz, herein called super dielectric materials (SDM, can be generated readily from common, inexpensive materials. Specifically it is demonstrated that high surface area alumina powders, loaded to the incipient wetness point with a solution of boric acid dissolved in water, have dielectric constants, near 0 Hz, greater than 4 × 108 in all cases, a remarkable increase over the best dielectric constants previously measured for energy storage capabilities, ca. 1 × 104. It is postulated that any porous, electrically insulating material (e.g., high surface area powders of silica, titania, etc., filled with a liquid containing a high concentration of ionic species will potentially be an SDM. Capacitors created with the first generated SDM dielectrics (alumina with boric acid solution, herein called New Paradigm Super (NPS capacitors display typical electrostatic capacitive behavior, such as increasing capacitance with decreasing thickness, and can be cycled, but are limited to a maximum effective operating voltage of about 0.8 V. A simple theory is presented: Water containing relatively high concentrations of dissolved ions saturates all, or virtually all, the pores (average diameter 500 Å of the alumina. In an applied field the positive ionic species migrate to the cathode end, and the negative ions to the anode end of each drop. This creates giant dipoles with high charge, hence leading to high dielectric constant behavior. At about 0.8 V, water begins to break down, creating enough ionic species to “short” the individual water droplets. Potentially NPS capacitor stacks can surpass “supercapacitors” in volumetric energy density.

  19. Effect of Wall Friction and Vortex Generation on Radial Void Distribution The Wall - Vortex Effect

    Energy Technology Data Exchange (ETDEWEB)

    Rouhani, Zia

    1974-09-15

    Arguments are presented to prove the existence of rolling vortices in two-phase flow. In liquid phase they will appear in a boundary layer near the walls while in the continuous vapor phase they will occur near the interface with a liquid film. The intensity and size of these vortices are expected to depend on the local velocity gradients normal to the walls. A discussion is given of the interaction between the rotational field associated with such vortices and bubbles in liquid flow or droplets in vapor-flow. This interaction is called the wall-vortex effect. It appears that several, apparently unrelated, phenomena observed in two-phase flow systems may be interpreted in terms of this mechanism. Among these are: Radial void peaking near the walls; Slip ratios less than unity observed even in vertical upward flow; Reduced droplet diffusion near the liquid film; Reduced vapor mixing between subchannels at low steam qualities; and Accelerated flashing process in flow of depressurized liquid. Finally, a comparison with the well-known Magnus effect is also included

  20. Post-breakdown secondary discharges at the electrode/dielectric interface of a cylindrical barrier discharge

    Science.gov (United States)

    Carman, Robert; Ward, Barry; Kane, Deborah

    2011-10-01

    The electrical breakdown characteristics of a double-walled cylindrical dielectric barrier discharge (DBD) lamp with a neon buffer gas under pulsed voltage excitation have been investigated. Following the formation of plasma in the main discharge gap, we have observed secondary breakdown phenomena at the inner and outer mesh electrode/dielectric interfaces under specific operating conditions. Plasma formation at these interfaces is investigated by monitoring the Ozone production rate in controlled flows of ultra high purity oxygen together with the overall electrical voltage-charge characteristics of the lamp. The results show that this secondary breakdown only occurs after the main discharge plasma has been established, and that significant electrical power may be dissipated in generating these spurious secondary plasmas. The results are important with regards to optimising the design and identifying efficient operating regimes of DBD based devices that employ mesh-type or wire/strip electrodes.

  1. Terahertz-frequency dielectric response of liquids

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd; Møller, Uffe; Cooke, David

    The dielectric response of liquids spans many decades in frequency. The dielectric response of a polar liquid is typically determined by relaxational dynamics of the dipolar moments of the liquid. In contrast, the dielectric response of a nonpolar liquid is determined by much weaker collision......-induced dipole moments. In the polar liquid water the fastest relaxational dynamics is found at terahertz frequencies, just below the first intermolecular vibrational and librational modes. In this presentation we will discuss optical terahertz spectroscopic techniques for measurement of the full dielectric...... function of liquids at terahertz frequencies. We will review the current understanding of the high-frequency dielectric spectrum of water, and discuss the relation between the dielectric spectrum and the thermodynamic properties of certain aqueous solutions....

  2. Silicone-based Dielectric Elastomers

    DEFF Research Database (Denmark)

    Skov, Anne Ladegaard

    Efficient conversion of energy from one form to another (transduction) is an important topic in our daily day, and it is a necessity in moving away from the fossil based society. Dielectric elastomers hold great promise as soft transducers, since they are compliant and light-weight amongst many...... energy efficient solutions are highly sought. These properties allow for interesting products ranging very broadly, e.g. from eye implants over artificial skins over soft robotics to huge wave energy harvesting plants. All these products utilize the inherent softness and compliance of the dielectric...... elastomer transducers. The subject of this thesis is improvement of properties of silicone-based dielectric elastomers with special focus on design guides towards electrically, mechanically, and electromechanically reliable elastomers. Strategies for improving dielectric elastomer performance are widely...

  3. Wake-field studies on photonic band gap accelerator cavities

    International Nuclear Information System (INIS)

    Li, D.; Kroll, N.; Stanford Linear Accelerator Center, M/S 26, P.O. Box 4349, Stanford, California; Smith, D.R.; Schultz, S.

    1997-01-01

    We have studied the wake-field of several metal Photonic Band Gap (PBG) cavities which consist of either a square or a hexagonal array of metal cylinders, bounded on top and bottom by conducting or superconducting sheets, surrounded by placing microwave absorber at the periphery or by replacing outer rows of metal cylinders with lossy dielectric ones, or by metallic walls. A removed cylinder from the center of the array constitutes a site defect where a localized electromagnetic mode can occur. While both monopole and dipole wake-fields have been studied, we confine our attention here mainly to the dipole case. The dipole wake-field is produced by modes in the propagation bands which tend to fill the entire cavity more or less uniformly and are thus easy to damp selectively. MAFIA time domain simulation of the transverse wake-field has been compared with that of a cylindrical pill-box comparison cavity. Even without damping the wake-field of the metal PBG cavity is substantially smaller than that of the pill-box cavity and may be further reduced by increasing the size of the lattice. By introducing lossy material at the periphery we have been able to produce Q factors for the dipole modes in the 40 to 120 range without significantly degrading the accelerating mode. copyright 1997 American Institute of Physics

  4. Life estimation and analysis of dielectric strength, hydrocarbon backbone and oxidation of high voltage multi stressed EPDM composites

    Science.gov (United States)

    Khattak, Abraiz; Amin, Muhammad; Iqbal, Muhammad; Abbas, Naveed

    2018-02-01

    Micro and nanocomposites of ethylene propylene diene monomer (EPDM) are recently studied for different characteristics. Study on life estimation and effects of multiple stresses on its dielectric strength and backbone scission and oxidation is also vital for endorsement of these composites for high voltage insulation and other outdoor applications. In order to achieve these goals, unfilled EPDM and its micro and nanocomposites are prepared at 23 phr micro silica and 6 phr nanosilica loadings respectively. Prepared samples are energized at 2.5 kV AC voltage and subjected for a long time to heat, ultraviolet radiation, acid rain, humidity and salt fog in accelerated manner in laboratory. Dielectric strength, leakage current and intensity of saturated backbone and carbonyl group are periodically measured. Loss in dielectric strength, increase in leakage current and backbone degradation and oxidation were observed in all samples. These effects were least in the case of EPDM nanocomposite. The nanocomposite sample also demonstrated longest shelf life.

  5. Temporal symmetry of individual filaments in different spatial symmetry filaments pattern in a dielectric barrier discharge

    International Nuclear Information System (INIS)

    Dong, L. F.; Xiao, H.; Fan, W. L.; Yin, Z. Q.; Zhao, H. T.

    2010-01-01

    The temporal behavior of individual filament in different spatial symmetry filaments patterns in dielectric barrier discharge is investigated by using an optical method. A series of return maps of the discharge moments of individual filaments is given. It is found that the temporal symmetry of individual filament changes with the change of the spatial symmetry of filaments pattern as the applied voltage increases. The role of wall charges for this phenomenon is analyzed.

  6. Theory of factors limiting high gradient operation of warm accelerating structures

    Energy Technology Data Exchange (ETDEWEB)

    Nusinovich, Gregory S. [University of Maryland; Antonsen, Thomas M. [University of Maryland; Kishek, Rami [University of Maryland

    2014-07-25

    This final report summarizes the research performed during the time period from 8/1/2010 to 7/31/2013. It consists of two parts describing our studies in two directions: (a) analysis of factors limiting operation of dielectric-loaded accelerating (DLA) structures where the main problem is the occurrence of multipactor on dielectric surfaces, and (b) studies of effects associated with either RF magnetic or RF electric fields which may cause the RF breakdown in high-gradient metallic accelerating structures. In the studies of DLA structures, at least, two accomplishments should be mentioned: the development of a 3D non-stationary, self-consistent code describing the multipactor phenomena and yielding very good agreement with some experimental data obtained in joint ANL/NRL experiments. In the metallic structures, such phenomena as the heating and melting of micro-particles (metallic dust) by RF electric and magnetic fields in single-shot and rep-rate regimes is analyzed. Also, such processes in micro-protrusions on the structure surfaces as heating and melting due to the field emitted current and the Nottingham effect are thoroughly investigated with the account for space charge of emitted current on the field emission from the tip.

  7. Optics of dielectric microstructures

    DEFF Research Database (Denmark)

    Søndergaard, Thomas

    2002-01-01

    From the work carried out within the ph.d. project two topics have been selected for this thesis, namely emission of radiation by sources in dielectric microstructures, and planar photonic crystal waveguides. The work done within the first topic, emission of radiation by sources in dielectric...... microstructures, will be presented in the part I of this thesis consisting of the chapters 2-5. An introductions is given in chapter 2. In part I three methods are presented for calculating spontaneous and classical emission from sources in dielectric microstructures. The first method presented in chapter 3...... is based on the Fermi Golden Rule, and spontaneous emission from emitters in a passive dielectric microstructure is calculated by summing over the emission into each electromagnetic mode of the radiation field. This method is applied to investigate spontaneous emission in a two-dimensional photonic crystal...

  8. Thermal dielectric function

    International Nuclear Information System (INIS)

    Moneta, M.

    1999-01-01

    Thermal dielectric functions ε(k,ω) for homogeneous electron gas were determined and discussed. The ground state of the gas is described by the Fermi-Dirac momentum distribution. The low and high temperature limits of ε(k,ω) were related to the Lindhard dielectric function and to ε(k, omega) derived for Boltzmann and for classical momentum distributions, respectively. (author)

  9. Several problems in accelerator shielding study

    International Nuclear Information System (INIS)

    Nakamura, Takashi; Hirayama, Hideo; Ban, Shuichi.

    1980-01-01

    Recently, the utilization of accelerators has increased rapidly, and the increase of accelerating energy and beam intensity is also remarkable. The studies on accelerator shielding have become important, because the amount of radiation emitted from accelerators increased, the regulation of the dose of environmental radiation was tightened, and the cost of constructing shielding rose. As the plans of constructing large accelerators have been made successively, the survey on the present state and the problems of the studies on accelerator shielding was carried out. Accelerators are classified into electron accelerators and proton accelerators in view of the studies on shielding. In order to start the studies on accelerator shielding, first, the preparation of the cross section data is indispensable. The cross sections for generating Bremsstrahlung, photonuclear reactions generating neutrons, generation of neutrons by hadrons, nuclear reaction of neutrons and generation of gamma-ray by hadrons are described. The generation of neutrons and gamma-ray as the problems of thick targets is explained. The shielding problems are complex and diversified, but in this paper, the studies on the shielding, by which basic data are obtainable, are taken up, such as beam damping and side wall shielding. As for residual radioactivity, main nuclides and the difference of residual radioactivity according to substances have been studied. (J.P.N.)

  10. On thick domain walls in general relativity

    Science.gov (United States)

    Goetz, Guenter; Noetzold, Dirk

    1989-01-01

    Planar scalar field configurations in general relativity differ considerably from those in flat space. It is shown that static domain walls of finite thickness in curved space-time do not possess a reflection symmetry. At infinity, the space-time tends to the Taub vacuum on one side of the wall and to the Minkowski vacuum (Rindler space-time) on the other. Massive test particles are always accelerated towards the Minkowski side, i.e., domain walls are attractive on the Taub side, but repulsive on the Minkowski side (Taub-vacuum cleaner). It is also proved that the pressure in all directions is always negative. Finally, a brief comment is made concerning the possibility of infinite, i.e., bigger than horizon size, domain walls in our universe. All of the results are independent of the form of the potential V(phi) greater than or equal to 0 of the scalar field phi.

  11. Accelerating universes driven by bulk particles

    International Nuclear Information System (INIS)

    Brito, F.A.; Cruz, F.F.; Oliveira, J.F.N.

    2005-01-01

    We consider our universe as a 3d domain wall embedded in a 5d dimensional Minkowski space-time. We address the problem of inflation and late time acceleration driven by bulk particles colliding with the 3d domain wall. The expansion of our universe is mainly related to these bulk particles. Since our universe tends to be permeated by a large number of isolated structures, as temperature diminishes with the expansion, we model our universe with a 3d domain wall with increasing internal structures. These structures could be unstable 2d domain walls evolving to fermi-balls which are candidates to cold dark matter. The momentum transfer of bulk particles colliding with the 3d domain wall is related to the reflection coefficient. We show a nontrivial dependence of the reflection coefficient with the number of internal dark matter structures inside the 3d domain wall. As the population of such structures increases the velocity of the domain wall expansion also increases. The expansion is exponential at early times and polynomial at late times. We connect this picture with string/M-theory by considering BPS 3d domain walls with structures which can appear through the bosonic sector of a five-dimensional supergravity theory

  12. Friction brake cushions acceleration and vibration loads

    Science.gov (United States)

    Fraser, G. F.; Zawadski, G. Z.

    1966-01-01

    Friction brake cushions an object in a vehicle from axially applied vibration and steady-state acceleration forces. The brake incorporates a doubly tapered piston that applies a controlled radial force to friction brake segments bearing against the walls of a cylinder.

  13. Dielectric Analysis for Torque of a Solute Ion Coulomb Force Monopole Motor

    Science.gov (United States)

    Fresco, Anthony N.

    ASME Technical Paper ES2010-90396 "Solute Ion Coulomb Force Monopole Motor and Solute Ion Linear Alignment Propulsion" by the author describes a motor that is based on an arrangement of solute ion electric field monopoles.[1] That is, through a process called capacitive deionization, sodium and chlorine ions in salt water are captured and confined by an electrically conductive material to form electric field monopoles. At least four of the like charged monopoles (all negative or all positive) can be arranged on a disc. At least one stationary monopole of the same charge is placed adjacent to the disc and positioned so that a repulsive electric field is formed between the stationary monopole and at least one of the monopoles positioned on the disc so that the disc is then forced to rotate a shaft at the center of the disc. This paper analyzes the behavior of the dielectric materials forming part of the monopoles to show that the net torque on the motor is greater than zero and also illustrates a novel effect of polarization of a dielectric material positioned between two like-charged monopoles as occurs in the configuration of the monopole motor and a deficiency in the conventional closed path analysis for work performed during movement of electric charges that emit electrostatic fields by failing to consider the effects of dielectric materials in shielding the electrostatic fields. The monopole motor connected to an to electrical generator can provide continuous on-board electrical power to electrical loads for local and deep space applications including power to electrode assemblies designed for linear alignment of like-charged solute ions as a means of propulsion and particle acceleration as described in the ES2010-90396 paper. Details of the monopole motor and the propulsion are available in WO 2008/024927 A2 (and US2010/0199632 A1) "Solute Ion Coulomb Force Acceleration and Electric Field Monopole Passive Voltage Source" by the author Ref.[2].

  14. Effects of the gate dielectric on the subthreshold transport of carbon nanotube network transistors grown by using plasma-enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Jeong, Seung Geun; Park, Wan Jun

    2010-01-01

    In this study, we investigated the subthreshold slope of random network carbon nanotube transistors with different geometries and passivations. Single-wall carbon nanotubes with lengths of 1-2 m were grown by using plasma-enhanced chemical vapor deposition to form the transistor channels. A critical channel length, where the subthreshold slope was saturated, of 7 μm was obtained. This was due to the percolational behavior of the nanotube random networks. With the dielectric passivation, the subthreshold slope was dramatically reduced from 9 V/decade to 0.9 V/decade by reducing interfacial trap sites, which then reduced the interface capacitance between the nanotube network and the gate dielectric.

  15. Structure and performance of dielectric films based on self-assembled nanocrystals with a high dielectric constant.

    Science.gov (United States)

    Huang, Limin; Liu, Shuangyi; Van Tassell, Barry J; Liu, Xiaohua; Byro, Andrew; Zhang, Henan; Leland, Eli S; Akins, Daniel L; Steingart, Daniel A; Li, Jackie; O'Brien, Stephen

    2013-10-18

    Self-assembled films built from nanoparticles with a high dielectric constant are attractive as a foundation for new dielectric media with increased efficiency and range of operation, due to the ability to exploit nanofabrication techniques and emergent electrical properties originating from the nanoscale. However, because the building block is a discrete one-dimensional unit, it becomes a challenge to capture potential enhancements in dielectric performance in two or three dimensions, frequently due to surface effects or the presence of discontinuities. This is a recurring theme in nanoparticle film technology when applied to the realm of thin film semiconductor and device electronics. We present the use of chemically synthesized (Ba,Sr)TiO3 nanocrystals, and a novel deposition-polymerization technique, as a means to fabricate the dielectric layer. The effective dielectric constant of the film is tunable according to nanoparticle size, and effective film dielectric constants of up to 34 are enabled. Wide area and multilayer dielectrics of up to 8 cm(2) and 190 nF are reported, for which the building block is an 8 nm nanocrystal. We describe models for assessing dielectric performance, and distinct methods for improving the dielectric constant of a nanocrystal thin film. The approach relies on evaporatively driven assembly of perovskite nanocrystals with uniform size distributions in a tunable 7-30 nm size range, coupled with the use of low molecular weight monomer/polymer precursor chemistry that can infiltrate the porous nanocrystal thin film network post assembly. The intercrystal void space (low k dielectric volume fraction) is minimized, while simultaneously promoting intercrystal connectivity and maximizing volume fraction of the high k dielectric component. Furfuryl alcohol, which has good affinity to the surface of (Ba,Sr)TiO3 nanocrystals and miscibility with a range of solvents, is demonstrated to be ideal for the production of nanocomposites. The

  16. limit loads for wall-thinning feeder pipes under combined bending and internal pressure

    International Nuclear Information System (INIS)

    Je, Jin Ho; Lee, Kuk Hee; Chung, Ha Joo; Kim, Ju Hee; Han, Jae Jun; Kim, Yun Jae

    2009-01-01

    Flow Accelerated Corrosion (FAC) during inservice conditions produces local wall-thinning in the feeder pipes of CANDU. The Wall-thinning in the feeder pipes is main degradation mechanisms affecting the integrity of piping systems. This paper discusses the integrity assessment of wall-thinned feeder pipes using limit load analysis. Based on finite element limit analyses, this paper compare limit loads for wall-thinning feeder pipes under combined bending and internal pressure with proposed limit loads. The limit loads are determined from limit analyses based on rectangular wall-thinning and elastic-perfectly-plastic materials using the large geometry change.

  17. Light in complex dielectrics

    NARCIS (Netherlands)

    Schuurmans, F.J.P.

    1999-01-01

    In this thesis the properties of light in complex dielectrics are described, with the two general topics of "modification of spontaneous emission" and "Anderson localization of light". The first part focuses on the spontaneous emission rate of an excited atom in a dielectric host with variable

  18. Wall thinning of piping in power plants

    International Nuclear Information System (INIS)

    Ohta, Joji; Inada, Fumio; Morita, Ryo; Kawai, Noboru; Yoneda, Kimitoshi

    2005-01-01

    Major mechanisms causing wall thinning of piping in power plants are flow accelerated corrosion (FAC), cavitation erosion and droplet erosion. Their fundamental aspects are reviewed on the basis of literature data. FAC is chemical process and it is affected by hydrodynamic factors, temperature, pH, dissolved oxygen concentration and chemical composition of materials. On the other hand, cavitation erosion and droplet erosion are mechanical process and they are mainly affected by hydrodynamic factors and mechanical properties of materials. Evaluation codes for FAC and mitigation methods of FAC and the erosion are also described. Wall thinning of piping is one of public concerns after an accident of a pipe failure at Mihama Nuclear Power Plant Unit 3, Kansai Electric Power Co., Inc., in August 2004. This paper gives comprehensive understanding of the wall thinning mechanism. (author)

  19. SOLVING BY PARALLEL COMPUTATION THE POISSON PROBLEM FOR HIGH INTENSITY BEAMS IN CIRCULAR ACCELERATORS

    International Nuclear Information System (INIS)

    LUCCIO, A.U.; DIMPERIO, N.L.; SAMULYAK, R.; BEEB-WANG, J.

    2001-01-01

    Simulation of high intensity accelerators leads to the solution of the Poisson Equation, to calculate space charge forces in the presence of acceleration chamber walls. We reduced the problem to ''two-and-a-half'' dimensions for long particle bunches, characteristic of large circular accelerators, and applied the results to the tracking code Orbit

  20. Magnesium diboride coated bulk niobium: a new approach to higher acceleration gradient

    Science.gov (United States)

    Civale, Leonardo; Tan, Teng; Wolak, M.; Xi, Xiaoxing; Tajima, Tsuyoshi

    Bulk niobium Superconducting Radio-Frequency cavities are a leading accelerator technology. Their performance is limited by the cavity loss and maximum acceleration gradient, which are negatively affected by vortex penetration into the superconductor when the peak magnetic field at the cavity wall surface exceeds the vortex penetration field (Hvp). It has been proposed that coating the inner wall of an SRF cavity with superconducting thin films increases Hvp. In this work, we utilized Nb ellipsoids to simulate an inverse SRF cavity and investigate the effect of coating it with magnesium diboride layer on the vortex penetration field. A significant enhancement of Hvp was observed. At 2.8 K, Hvp increased from 2100 Oe for an uncoated Nb ellipsoid to 2700 Oe for a Nb ellipsoid coated with 200 nm thick MgB2 thin film. This finding creates a new route towards achieving higher acceleration gradient in SRF cavity accelerator beyond the theoretical limit of bulk Nb.

  1. Experimental results in superconducting niobium resonators for high-brightness ion beam acceleration

    International Nuclear Information System (INIS)

    Delayen, J.R.; Bohn, C.L.; Roche, C.T.

    1991-01-01

    Two niobium resonant cavities for high-brightness ion beam acceleration have been constructed and tested. The first was based on a coaxial quarter-wave geometry and was optimized for phase velocity β O = O.15. This cavity, which resonates at 400 MHz in the fundamental mode, operated at an average (wall-to-wall) accelerating gradient of 12.9 MV/m under continuous-wave (cw) fields. At this gradient, a cavity Q of 1.4x10 8 was measured. The second was based on a coaxial half-wave geometry and was optimized for β O = 0.12. This cavity, which resonates at 355 MHz in the fundamental mode, operated at an average accelerating gradient of 18.0 MV/m under cw fields. This is the highest average accelerating gradient achieved to date in low-velocity structures designed for cw operation. At this gradient, a cavity Q of 1.2 x 10 8 was measured

  2. Dielectric Modulated FET (DMFET)

    Indian Academy of Sciences (India)

    First page Back Continue Last page Graphics. Working Principle: Change in Dielectric constant due to immobilization of biomolecules in the nanogap cavity leads to change in effective gate capacitance and thus gate bias for FET. Working Principle: Change in Dielectric constant due to immobilization of biomolecules in the ...

  3. Analytical solutions of nonlocal Poisson dielectric models with multiple point charges inside a dielectric sphere

    Science.gov (United States)

    Xie, Dexuan; Volkmer, Hans W.; Ying, Jinyong

    2016-04-01

    The nonlocal dielectric approach has led to new models and solvers for predicting electrostatics of proteins (or other biomolecules), but how to validate and compare them remains a challenge. To promote such a study, in this paper, two typical nonlocal dielectric models are revisited. Their analytical solutions are then found in the expressions of simple series for a dielectric sphere containing any number of point charges. As a special case, the analytical solution of the corresponding Poisson dielectric model is also derived in simple series, which significantly improves the well known Kirkwood's double series expansion. Furthermore, a convolution of one nonlocal dielectric solution with a commonly used nonlocal kernel function is obtained, along with the reaction parts of these local and nonlocal solutions. To turn these new series solutions into a valuable research tool, they are programed as a free fortran software package, which can input point charge data directly from a protein data bank file. Consequently, different validation tests can be quickly done on different proteins. Finally, a test example for a protein with 488 atomic charges is reported to demonstrate the differences between the local and nonlocal models as well as the importance of using the reaction parts to develop local and nonlocal dielectric solvers.

  4. Dielectric properties of binary solutions a data handbook

    CERN Document Server

    Akhadov, Y Y

    1980-01-01

    Dielectric Properties of Binary Solutions focuses on the investigation of the dielectric properties of solutions, as well as the molecular interactions and mechanisms of molecular processes that occur in liquids. The book first discusses the fundamental formulas describing the dielectric properties of liquids and dielectric data for binary systems of non-aqueous solutions. Topics include permittivity and dielectric dispersion parameters of non-aqueous solutions of organic and inorganic compounds. The text also tackles dielectric data for binary systems of aqueous solutions, including permittiv

  5. Observations on out-of-plane behaviour of URM walls in buildings with RC slabs

    OpenAIRE

    Tondelli, Marco; Beyer, Katrin

    2014-01-01

    In Switzerland many new residential buildings are constructed as unreinforced masonry (URM) structures or as mixed structures where URM walls are coupled with reinforced concrete (RC) walls by RC slabs. At present the boundary conditions of URM walls subjected to out-of-plane accelerations are still not well quantified. In the framework of a large research activity on RC-URM wall structures a shake-table test on a four-storey mixed structure was performed. The test specimen, which was built a...

  6. Silver Nanowire/MnO2 Nanowire Hybrid Polymer Nanocomposites: Materials with High Dielectric Permittivity and Low Dielectric Loss.

    Science.gov (United States)

    Zeraati, Ali Shayesteh; Arjmand, Mohammad; Sundararaj, Uttandaraman

    2017-04-26

    This study reports the fabrication of hybrid nanocomposites based on silver nanowire/manganese dioxide nanowire/poly(methyl methacrylate) (AgNW/MnO 2 NW/PMMA), using a solution casting technique, with outstanding dielectric permittivity and low dielectric loss. AgNW was synthesized using the hard-template technique, and MnO 2 NW was synthesized employing a hydrothermal method. The prepared AgNW:MnO 2 NW (2.0:1.0 vol %) hybrid nanocomposite showed a high dielectric permittivity (64 at 8.2 GHz) and low dielectric loss (0.31 at 8.2 GHz), which are among the best reported values in the literature in the X-band frequency range (8.2-12.4 GHz). The superior dielectric properties of the hybrid nanocomposites were attributed to (i) dimensionality match between the nanofillers, which increased their synergy, (ii) better dispersion state of AgNW in the presence of MnO 2 NW, (iii) positioning of ferroelectric MnO 2 NW in between AgNWs, which increased the dielectric permittivity of nanodielectrics, thereby increasing dielectric permittivity of the hybrid nanocomposites, (iv) barrier role of MnO 2 NW, i.e., cutting off the contact spots of AgNWs and leading to lower dielectric loss, and (v) AgNW aligned structure, which increased the effective surface area of AgNWs, as nanoelectrodes. Comparison of the dielectric properties of the developed hybrid nanocomposites with the literature highlights their great potential for flexible capacitors.

  7. Dielectric spectroscopy of Ag-starch nanocomposite films

    Science.gov (United States)

    Meena; Sharma, Annu

    2018-04-01

    In the present work Ag-starch nanocomposite films were fabricated via chemical reduction route. The formation of Ag nanoparticles was confirmed using transmission electron microscopy (TEM). Further the effect of varying concentration of Ag nanoparticles on the dielectric properties of starch has been studied. The frequency response of dielectric constant (ε‧), dielectric loss (ε″) and dissipation factor tan(δ) has been studied in the frequency range of 100 Hz to 1 MHz. Dielectric data was further analysed using Cole-Cole plots. The dielectric constant of starch was found to be 4.4 which decreased to 2.35 in Ag-starch nanocomposite film containing 0.50 wt% of Ag nanoparticles. Such nanocomposites with low dielectric constant have potential applications in microelectronic technologies.

  8. Dielectric properties of lunar surface

    Science.gov (United States)

    Yushkova, O. V.; Kibardina, I. N.

    2017-03-01

    Measurements of the dielectric characteristics of lunar soil samples are analyzed in the context of dielectric theory. It has been shown that the real component of the dielectric permittivity and the loss tangent of rocks greatly depend on the frequency of the interacting electromagnetic field and the soil temperature. It follows from the analysis that one should take into account diurnal variations in the lunar surface temperature when interpreting the radar-sounding results, especially for the gigahertz radio range.

  9. Dielectric relaxation and ac conduction in γ-irradiated UHMWPE/MWCNTs nano composites: Impedance spectroscopy analysis

    International Nuclear Information System (INIS)

    Maqbool, Syed Asad; Mehmood, Malik Sajjad; Mukhtar, Saqlain Saqib; Baluch, Mansoor A.; Khan, Shamim; Yasin, Tariq; Khan, Yaqoob

    2017-01-01

    The dielectric behavior of γ-irradiated ultra-high molecular weight polyethylene (UHMWPE) and its nano composites (NCs) with γ-ray modified multi wall carbon nano tubes (γ-MWCNTs) and MWCNTs had been studied using impedance spectroscopy. The study had been carried out in the frequency range of 20–2 MHz at room temperature. All samples (pure and NCs) were prepared in the form of sheets and irradiated with γ-dose of 50 kGy and 100 kGy, respectively. The comprehensive analysis of results revealed that resistivity of UHMWPE for conduction decreased on irradiation and incorporation of MWCNTs (whether γ ray modified or un-modified) due to the radiation induced damage and conductive networks induced by MWCNTs. At low frequency range a significant increase in the dielectric constant had been observed because of irradiation and addition of MWNCTs. The trend of loss tangent and ac conductivity for each investigated sample depended on resistivity offered and had a decreasing trend as a function of frequency. Moreover, dissipation factor increased with the incorporation of MWNCTs and irradiation from 0.12 to 0.22. In addition to this, non-frequency dependent static dielectric constant was also found to increase with irradiation and incorporation of MWCNTs. The relaxation time was found to increase from 1.2 to 4.3 ms due to hindrance offered by radiation induced mutual cross linking of PE chains and polymer-MWNCTs bindings. - Highlights: • The resistivity for conduction in pristine UHMWPE is decreased with γ-irradiation. • Conduction in PE/MWCNTs nanocomposites increased due to MWCNTs addition. • Static dielectric constant of UHMWPE increased with γ-irradiation. • Static dielectric constant of UHMWPE increased due to MWCNTs incorporation.

  10. Numerical investigation of dielectric barrier discharges

    Science.gov (United States)

    Li, Jing

    1997-12-01

    A dielectric barrier discharge (DBD) is a transient discharge occurring between two electrodes in coaxial or planar arrangements separated by one or two layers of dielectric material. The charge accumulated on the dielectric barrier generates a field in a direction opposite to the applied field. The discharge is quenched before an arc is formed. It is one of the few non-thermal discharges that operates at atmospheric pressure and has the potential for use in pollution control. In this work, a numerical model of the dielectric barrier discharge is developed, along with the numerical approach. Adaptive grids based on the charge distribution is used. A self-consistent method is used to solve for the electric field and charge densities. The Successive Overrelaxation (SOR) method in a non-uniform grid spacing is used to solve the Poisson's equation in the cylindrically-symmetric coordinate. The Flux Corrected Transport (FCT) method is modified to solve the continuity equations in the non-uniform grid spacing. Parametric studies of dielectric barrier discharges are conducted. General characteristics of dielectric barrier discharges in both anode-directed and cathode-directed streamer are studied. Effects of the dielectric capacitance, the applied field, the resistance in external circuit and the type of gases (O2, air, N2) are investigated. We conclude that the SOR method in an adaptive grid spacing for the solution of the Poisson's equation in the cylindrically-symmetric coordinate is convergent and effective. The dielectric capacitance has little effect on the g-factor of radical production, but it determines the strength of the dielectric barrier discharge. The applied field and the type of gases used have a significant role on the current peak, current pulse duration and radical generation efficiency, discharge strength, and microstreamer radius, whereas the external series resistance has very little effect on the streamer properties. The results are helpful in

  11. Optimisation of Silicone-based Dielectric Elastomer Transducers by Means of Block Copolymers - Synthesis and Compounding

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam

    through the use of a multi-walled carbon nanotube (MWCNT) in a PDMS-PEG matrix as a compliant electrode of dielectric elastomers. The conductive PDMS-PEG copolymer was incorporated with surface-treated MWCNT, in order to obtain highly conductive elastomer. The prepared sample with 4 parts per hundred...... enhancing the electrical breakdown strength of silicone by using an aromatic voltage stabiliser. Here, polyphenylmethylsiloxane (PPMS), which contained aromatic voltage stabilisers, was bonded covalently to PDMS through a hydrosilylation reaction obtaining PDMS-PPMS copolymers. The synthesised copolymers...

  12. Spin-orbit coupling and the static polarizability of single-wall carbon nanotubes

    International Nuclear Information System (INIS)

    Diniz, Ginetom S.; Ulloa, Sergio E.

    2014-01-01

    We calculate the static longitudinal polarizability of single-wall carbon tubes in the long wavelength limit taking into account spin-orbit effects. We use a four-orbital orthogonal tight-binding formalism to describe the electronic states and the random phase approximation to calculate the dielectric function. We study the role of both the Rashba as well as the intrinsic spin-orbit interactions on the longitudinal dielectric response, i.e., when the probing electric field is parallel to the nanotube axis. The spin-orbit interaction modifies the nanotube electronic band dispersions, which may especially result in a small gap opening in otherwise metallic tubes. The bandgap size and state features, the result of competition between Rashba and intrinsic spin-orbit interactions, result in drastic changes in the longitudinal static polarizability of the system. We discuss results for different nanotube types and the dependence on nanotube radius and spin-orbit couplings.

  13. Spin-orbit coupling and the static polarizability of single-wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Diniz, Ginetom S., E-mail: ginetom@gmail.com; Ulloa, Sergio E. [Department of Physics and Astronomy and Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701-2979 (United States)

    2014-07-14

    We calculate the static longitudinal polarizability of single-wall carbon tubes in the long wavelength limit taking into account spin-orbit effects. We use a four-orbital orthogonal tight-binding formalism to describe the electronic states and the random phase approximation to calculate the dielectric function. We study the role of both the Rashba as well as the intrinsic spin-orbit interactions on the longitudinal dielectric response, i.e., when the probing electric field is parallel to the nanotube axis. The spin-orbit interaction modifies the nanotube electronic band dispersions, which may especially result in a small gap opening in otherwise metallic tubes. The bandgap size and state features, the result of competition between Rashba and intrinsic spin-orbit interactions, result in drastic changes in the longitudinal static polarizability of the system. We discuss results for different nanotube types and the dependence on nanotube radius and spin-orbit couplings.

  14. Oblique surface waves at an interface between a metal-dielectric superlattice and an isotropic dielectric

    International Nuclear Information System (INIS)

    Vuković, Slobodan M; Miret, Juan J; Zapata-Rodriguez, Carlos J; Jakšić, Zoran

    2012-01-01

    We investigate the existence and dispersion characteristics of surface waves that propagate at an interface between a metal-dielectric superlattice and an isotropic dielectric. Within the long-wavelength limit, when the effective-medium (EM) approximation is valid, the superlattice behaves like a uniaxial plasmonic crystal with the main optical axes perpendicular to the metal-dielectric interfaces. We demonstrate that if such a semi-infinite plasmonic crystal is cut normally to the layer interfaces and brought into contact with a semi-infinite dielectric, a new type of surface mode can appear. Such modes can propagate obliquely to the optical axes if favorable conditions regarding the thickness of the layers and the dielectric permittivities of the constituent materials are met. We show that losses within the metallic layers can be substantially reduced by making the layers sufficiently thin. At the same time, a dramatic enlargement of the range of angles for oblique propagation of the new surface modes is observed. This can lead, however, to field non-locality and consequently to failure of the EM approximation.

  15. Cellulose Triacetate Dielectric Films For Capacitors

    Science.gov (United States)

    Yen, Shiao-Ping S.; Jow, T. Richard

    1994-01-01

    Cellulose triacetate investigated for use as dielectric material in high-energy-density capacitors for pulsed-electrical-power systems. Films of cellulose triacetate metalized on one or both sides for use as substrates for electrodes and/or as dielectrics between electrodes in capacitors. Used without metalization as simple dielectric films. Advantages include high breakdown strength and self-healing capability.

  16. Beam energy reduction in an acceleration gap

    International Nuclear Information System (INIS)

    Rhee, M.J.

    1990-01-01

    The subject of high-current accelerators has recently attracted considerable attention. The high-current beam accompanies a substantial amount of field energy in the space between the beam and the drift tube wall, as it propagates through a conducting drift tube of accelerator system. While such a beam is being accelerated in a gap, this field energy is subject to leak through the opening of the gap. The amount of energy lost in the gap is replenished by the beam at the expense of its kinetic energy. In this paper, the authors present a simple analysis of field energy loss in an acceleration gap for a relativistic beam for which beam particle velocity equals to c. It is found that the energy loss, which in turn reduces the beam kinetic energy, is ΔV = IZ 0 : the beam current times the characteristic impedance of the acceleration gap. As a result, the apparent acceleration voltage of the gap is reduced from the applied voltage by ΔV. This effect, especially for generation of high-current beam accelerated by a multigap accelerator, appears to be an important design consideration. The energy reduction mechanism and a few examples are presented

  17. Theoretical and Experimental Studies in Accelerator Physics

    Energy Technology Data Exchange (ETDEWEB)

    Rosenzweig, James [Univ. of California, Los Angeles, CA (United States). Dept. of Physics and Astronomy

    2017-03-08

    . We note also that PBPL graduates remain as close elaborators for the program after leaving UCLA. The UCLA PBPL program is a foremost developer of on-campus facilities, such as the Neptune and Pegasus Laboratories, providing a uniquely strong environment for student-based research. In addition, the PBPL is a strong user of off-campus national lab facilities, such as SLAC FACET and NLCTA, and the BNL ATF. UCLA has also vigorously participated in the development of these facilities. The dual emphases on off- and on-campus opportunities permit the PBPL to address in an agile way a wide selection of cutting-edge research topics. The topics embraced by this proposal illustrate this program aspect well. These include: GV/m dielectric wakefield acceleration/coherent Cerenkov radiation experiments at FACET (E-201) and the ATF; synergistic laser-excited dielectric accelerator and light source development; plasma wakefield (PWFA) experiments on “Trojan horse” ionization injection (FACET E-210), quasi-nonlinear PWFA at BNL and the production at Neptune high transformer ratio plasma wakes; the inauguration of a new type of RF photoinjector termed “hybrid” at UCLA, and application to PWFA; space-charge dominated beam and cathode/near cathode physics; the study of advanced IFEL systems, for very high energy gain and utilization of novel OAM modes; the physcis of inverse Compton scattering (ICS), with applications to e+ production and γγ colliders; electron diffraction; and advanced beam diagnostics using coherent imaging techniques. These subjects are addressed under the leadership of PBPL director Prof. James Rosenzweig in Task A, and Prof. Pietro Musumeci in Task J, which was initiated following his OHEP Outstanding Junior Investigator award.

  18. Direct measurement of wall shear stress in a reattaching flow with a photonic sensor

    International Nuclear Information System (INIS)

    Ayaz, U K; Ioppolo, T; Ötügen, M V

    2013-01-01

    Wall shear stress measurements are carried out in a planar backward-facing step flow using a micro-optical sensor. The sensor is essentially a floating element system and measures the shear stress directly. The transduction method to measure the floating element deflection is based on the whispering gallery optical mode (WGM) shifts of a dielectric microsphere. This method is capable of measuring floating element displacements of the order of a nanometer. The floating element surface is circular with a diameter of ∼960 µm, which is part of a beam that is in contact with the dielectric microsphere. The sensor is calibrated for shear stress as well as pressure sensitivity yielding 7.3 pm Pa −1 and 0.0236 pm Pa −1 for shear stress and pressure sensitivity, respectively. Hence, the contribution by the wall pressure is less than two orders of magnitude smaller than that of shear stress. Measurements are made for a Reynolds number range of 2000–5000 extending to 18 step heights from the step face. The results are in good agreement with those of earlier reports. An analysis is also carried out to evaluate the performance of the WGM sensor including measurement sensitivity and bandwidth. (paper)

  19. Automated qualification and analysis of protective spark gaps for DC accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Srutarshi; Rajan, Rehim N.; Dewangan, S.; Sharma, D.K.; Patel, Rupesh; Bakhtsingh, R.I.; Gond, Seema; Waghmare, Abhay; Thakur, Nitin; Mittal, K.C. [Accelerator and Pulse Power Division, Bhabha Atomic Research Centre, Mumbai (India)

    2014-07-01

    Protective spark gaps are used in the high voltage multiplier column of a 3 MeV DC Accelerator to prevent excessive voltage build-ups. Precise gap of 5 mm is maintained between the electrodes in these spark gaps for obtaining 120 kV± 5 kV in 6 kg/cm{sup 2} SF{sub 6} environment which is the dielectric medium. There are 74 such spark gaps used in the multiplier. Each spark gap has to be qualified for electrical performance before fitting in the accelerator to ensure reliable operation. As the breakdown voltage stabilizes after a large number of sparks between the electrodes, the qualification process becomes time consuming and cumbersome. For qualifying large number of spark gaps an automatic breakdown analysis setup has been developed. This setup operates in air, a dielectric medium. The setup consists of a flyback topology based high voltage power supply with maximum rating of 25 kV. This setup works in conjunction with spark detection and automated shutdown circuit. The breakdown voltage is sensed using a peak detector circuit. The voltage breakdown data is recorded and statistical distribution of the breakdown voltage has been analyzed. This paper describes details of the diagnostics and the spark gap qualification process based on the experimental data. (author)

  20. Using Piezoelectric Devices to Transmit Power through Walls

    Science.gov (United States)

    Sherrit, Stewart; Bar-Cohen, Yoseph; Bao, Xiaoqi

    2008-01-01

    A method denoted wireless acoustic-electric feed-through (WAEF) has been conceived for transmitting power and/or data signals through walls or other solid objects made of a variety of elastic materials that could be electrically conductive or nonconductive. WAEF would make it unnecessary to use wires, optical fibers, tubes, or other discrete wall-penetrating signal-transmitting components, thereby eliminating the potential for structural weakening or leakage at such penetrations. Avoidance of such penetrations could be essential in some applications in which maintenance of pressure, vacuum, or chemical or biological isolation is required. In a basic WAEF setup, a transmitting piezoelectric transducer on one side of a wall would be driven at resonance to excite ultrasonic vibrations in the wall. A receiving piezoelectric transducer on the opposite side of the wall would convert the vibrations back to an ultrasonic AC electric signal, which would then be detected and otherwise processed in a manner that would depend on the modulation (if any) applied to the signal and whether the signal was used to transmit power, data, or both. An electromechanical-network model has been derived as a computationally efficient means of analyzing and designing a WAEF system. This model is a variant of a prior model, known in the piezoelectric-transducer art as Mason's equivalent-circuit model, in which the electrical and mechanical dynamics, including electromechanical couplings, are expressed as electrical circuit elements that can include inductors, capacitors, and lumped-parameter complex impedances. The real parts of the complex impedances are used to account for dielectric, mechanical, and coupling losses in all components (including all piezoelectric-transducer, wall, and intermediate material layers). In an application to a three-layer piezoelectric structure, this model was shown to yield the same results as do solutions of the wave equations of piezoelectricity and acoustic

  1. Electric field simulation and measurement of a pulse line ion accelerator

    International Nuclear Information System (INIS)

    Shen Xiaokang; Zhang Zimin; Cao Shuchun; Zhao Hongwei; Zhao Quantang; Liu Ming; Jing Yi; Wang Bo; Shen Xiaoli

    2012-01-01

    An oil dielectric helical pulse line to demonstrate the principles of a Pulse Line Ion Accelerator (PLIA) has been designed and fabricated. The simulation of the axial electric field of an accelerator with CST code has been completed and the simulation results show complete agreement with the theoretical calculations. To fully understand the real value of the electric field excited from the helical line in PLIA, an optical electric integrated electric field measurement system was adopted. The measurement result shows that the real magnitude of axial electric field is smaller than that calculated, probably due to the actual pitch of the resister column which is much less than that of helix. (authors)

  2. Bioactive surface modifications on inner walls of poly-tetra-fluoro-ethylene tubes using dielectric barrier discharge

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Yong Ki [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Heat Treatment and Surface Engineering R and D Group, Korea Institute of Industrial Technology, Incheon 406-840 (Korea, Republic of); Park, Daewon; Kim, Hoonbae [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Lee, Hyerim; Park, Heonyong [Department of Molecular Biology, Dankook University, Yongin 448-701 (Korea, Republic of); Kim, Hong Ja [Department of Internal Medicine, Dankook University, Cheonan 330-714 (Korea, Republic of); Jung, Donggeun, E-mail: djung@skku.ac.kr [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2014-03-01

    Graphical abstract: - Highlights: • The surface modification of the inner walls of poly-tetra-fluoro-ethylene (PTFE) tubing was carried out to improve vascular grafts. • Focus was centered on the cell attachment of the inner wall of the PTFE by sequential processes of hydrogen plasma treatment, hydrocarbon deposition, and reactive plasma treatment using micro plasma discharge. - Abstract: Bioactive surface modification can be used in a variety of medical polymeric materials in the fields of biochips and biosensors, artificial membranes, and vascular grafts. In this study, the surface modification of the inner walls of poly-tetra-fluoro-ethylene (PTFE) tubing was carried out to improve vascular grafts, which are made of biocompatible material for the human body in the medical field. Focus was centered on the cell attachment of the inner wall of the PTFE by sequential processes of hydrogen plasma treatment, hydrocarbon deposition, and reactive plasma treatment on the PFTE surface using micro plasma discharge. Micro plasma was generated by a medium-frequency alternating current high-voltage generator. The preliminary modification of PTFE was conducted by a plasma of hydrogen and argon gases. The hydrocarbon thin film was deposited on modified PTFE with a mixture of acetylene and argon gases. The reactive plasma treatment using oxygen plasma was done to give biocompatible functionality to the inner wall surface. The hydrophobic surface of bare PTFE is made hydrophilic by the reactive plasma treatment due to the formation of carbonyl groups on the surface. The reactive treatment could lead to improved attachment of smooth muscle cells (SMCs) on the modified PTFE tubing. Fourier transform infrared absorption spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and water contact angle measurement were used for the analysis of the surface modification. The SMC-attached PTFE tube developed will be applicable to in vitro human vasculature

  3. Bioactive surface modifications on inner walls of poly-tetra-fluoro-ethylene tubes using dielectric barrier discharge

    International Nuclear Information System (INIS)

    Cho, Yong Ki; Park, Daewon; Kim, Hoonbae; Lee, Hyerim; Park, Heonyong; Kim, Hong Ja; Jung, Donggeun

    2014-01-01

    Graphical abstract: - Highlights: • The surface modification of the inner walls of poly-tetra-fluoro-ethylene (PTFE) tubing was carried out to improve vascular grafts. • Focus was centered on the cell attachment of the inner wall of the PTFE by sequential processes of hydrogen plasma treatment, hydrocarbon deposition, and reactive plasma treatment using micro plasma discharge. - Abstract: Bioactive surface modification can be used in a variety of medical polymeric materials in the fields of biochips and biosensors, artificial membranes, and vascular grafts. In this study, the surface modification of the inner walls of poly-tetra-fluoro-ethylene (PTFE) tubing was carried out to improve vascular grafts, which are made of biocompatible material for the human body in the medical field. Focus was centered on the cell attachment of the inner wall of the PTFE by sequential processes of hydrogen plasma treatment, hydrocarbon deposition, and reactive plasma treatment on the PFTE surface using micro plasma discharge. Micro plasma was generated by a medium-frequency alternating current high-voltage generator. The preliminary modification of PTFE was conducted by a plasma of hydrogen and argon gases. The hydrocarbon thin film was deposited on modified PTFE with a mixture of acetylene and argon gases. The reactive plasma treatment using oxygen plasma was done to give biocompatible functionality to the inner wall surface. The hydrophobic surface of bare PTFE is made hydrophilic by the reactive plasma treatment due to the formation of carbonyl groups on the surface. The reactive treatment could lead to improved attachment of smooth muscle cells (SMCs) on the modified PTFE tubing. Fourier transform infrared absorption spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and water contact angle measurement were used for the analysis of the surface modification. The SMC-attached PTFE tube developed will be applicable to in vitro human vasculature

  4. Effects of reactive oxygen species on cellular wall disassembly of banana fruit during ripening.

    Science.gov (United States)

    Cheng, Guiping; Duan, Xuewu; Shi, John; Lu, Wangjin; Luo, Yunbo; Jiang, Weibo; Jiang, Yueming

    2008-07-15

    Fruit softening is generally attributed to cell wall disassembly. Experiments were conducted to investigate effects of various reactive oxygen species (ROS) on in vitro cellular wall disassembly of harvested banana fruit. The alcohol-extracted insoluble residue (AEIR) was obtained from the pulp tissues of banana fruit at various ripening stages and then used to examine the disassembly of cellular wall polysaccharides in the presence of superoxide anion (O2(-)), hydrogen peroxide (H2O2) or hydroxyl radical (OH) and their scavengers. The presence of OH accelerated significantly disassembly of cellular wall polysaccharides in terms of the increase in contents of total sugars released and uronic acid, and the decrease in molecular mass of soluble polysaccharides, using gel permeation chromatography. However, the treatment with H2O2 or O2(-) showed no significant effect on the disassembly of cellular wall polysaccharides. Furthermore, the degradation of the de-esterified AEIR was more susceptible to OH attack than the esterified AEIR. In addition, the effect of OH could be inhibited in the presence of OH scavenger. This study suggests that disassembly of cellular wall polysaccharides could be initiated by OH as the solublisation of the polysaccharides increased, which, in turn, accelerated fruit softening. Copyright © 2008 Elsevier Ltd. All rights reserved.

  5. Investigation of the dielectric properties of shale

    International Nuclear Information System (INIS)

    Martemyanov, Sergey M.

    2011-01-01

    The article is dedicated to investigation of the dielectric properties of oil shale. Investigations for samples prepared from shale mined at the deposit in Jilin Province in China were done. The temperature and frequency dependences of rock characteristics needed to calculate the processes of their thermal processing are investigated. Frequency dependences for the relative dielectric constant and dissipation factor of rock in the frequency range from 0,1 Hz to 1 MHz are investigated. The temperature dependences for rock resistance, dielectric capacitance and dissipation factor in the temperature range from 20 to 600°C are studied. Key words: shale, dielectric properties, relative dielectric constant, dissipation factor, temperature dependence, frequency dependence

  6. Substrate clamping effects on irreversible domain wall dynamics in lead zirconate titanate thin films.

    Science.gov (United States)

    Griggio, F; Jesse, S; Kumar, A; Ovchinnikov, O; Kim, H; Jackson, T N; Damjanovic, D; Kalinin, S V; Trolier-McKinstry, S

    2012-04-13

    The role of long-range strain interactions on domain wall dynamics is explored through macroscopic and local measurements of nonlinear behavior in mechanically clamped and released polycrystalline lead zirconate-titanate (PZT) films. Released films show a dramatic change in the global dielectric nonlinearity and its frequency dependence as a function of mechanical clamping. Furthermore, we observe a transition from strong clustering of the nonlinear response for the clamped case to almost uniform nonlinearity for the released film. This behavior is ascribed to increased mobility of domain walls. These results suggest the dominant role of collective strain interactions mediated by the local and global mechanical boundary conditions on the domain wall dynamics. The work presented in this Letter demonstrates that measurements on clamped films may considerably underestimate the piezoelectric coefficients and coupling constants of released structures used in microelectromechanical systems, energy harvesting systems, and microrobots.

  7. Dielectric inspection of erythrocyte morphology

    International Nuclear Information System (INIS)

    Hayashi, Yoshihito; Oshige, Ikuya; Katsumoto, Yoichi; Omori, Shinji; Yasuda, Akio; Asami, Koji

    2008-01-01

    We performed a systematic study of the sensitivity of dielectric spectroscopy to erythrocyte morphology. Namely, rabbit erythrocytes of four different shapes were prepared by precisely controlling the pH of the suspending medium, and their complex permittivities over the frequency range from 0.1 to 110 MHz were measured and analyzed. Their quantitative analysis shows that the characteristic frequency and the broadening parameter of the dielectric relaxation of interfacial polarization are highly specific to the erythrocyte shape, while they are insensitive to the cell volume fraction. Therefore, these two dielectric parameters can be used to differentiate erythrocytes of different shapes, if dielectric spectroscopy is applied to flow-cytometric inspection of single blood cells. In addition, we revealed the applicability and limitations of the analytical theory of interfacial polarization to explain the experimental permittivities of non-spherical erythrocytes

  8. Dielectric inspection of erythrocyte morphology

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Yoshihito; Oshige, Ikuya; Katsumoto, Yoichi; Omori, Shinji; Yasuda, Akio [Life Science Laboratory, Materials Laboratories, Sony Corporation, Sony Bioinformatics Center, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510 (Japan); Asami, Koji [Laboratory of Molecular Aggregation Analysis, Division of Multidisciplinary Chemistry, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan)], E-mail: Yoshihito.Hayashi@jp.sony.com

    2008-05-21

    We performed a systematic study of the sensitivity of dielectric spectroscopy to erythrocyte morphology. Namely, rabbit erythrocytes of four different shapes were prepared by precisely controlling the pH of the suspending medium, and their complex permittivities over the frequency range from 0.1 to 110 MHz were measured and analyzed. Their quantitative analysis shows that the characteristic frequency and the broadening parameter of the dielectric relaxation of interfacial polarization are highly specific to the erythrocyte shape, while they are insensitive to the cell volume fraction. Therefore, these two dielectric parameters can be used to differentiate erythrocytes of different shapes, if dielectric spectroscopy is applied to flow-cytometric inspection of single blood cells. In addition, we revealed the applicability and limitations of the analytical theory of interfacial polarization to explain the experimental permittivities of non-spherical erythrocytes.

  9. Laser amplification in excited dielectrics

    DEFF Research Database (Denmark)

    Winkler, Thomas; Haahr-Lillevang, Lasse; Sarpe, Cristian

    2018-01-01

    Wide-bandgap dielectrics such as glasses or water are transparent at visible and infrared wavelengths. This changes when they are exposed to ultrashort and highly intense laser pulses. Different interaction mechanisms lead to the appearance of various transient nonlinear optical phenomena. Using...... these, the optical properties of dielectrics can be controlled from the transparent to the metal-like state. Here we expand this range by a yet unexplored mechanism in excited dielectrics: amplification. In a two-colour pump-probe experiment, we show that a 400nm femtosecond laser pulse is coherently...

  10. Electrical breakdown phenomena of dielectric elastomers

    DEFF Research Database (Denmark)

    Mateiu, Ramona Valentina; Yu, Liyun; Skov, Anne Ladegaard

    2017-01-01

    Silicone elastomers have been heavily investigated as candidates for dielectric elastomers and are as such almost ideal candidates with their inherent softness and compliance but they suffer from low dielectric permittivity. This shortcoming has been sought optimized by many means during recent...... years. However, optimization with respect to the dielectric permittivity solely may lead to other problematic phenomena such as premature electrical breakdown. In this work, we investigate the electrical breakdown phenomena of various types of permittivity-enhanced silicone elastomers. Two types...... of silicone elastomers are investigated and different types of breakdown are discussed. Furthermore the use of voltage stabilizers in silicone-based dielectric elastomers is investigated and discussed....

  11. Applicability of point-dipoles approximation to all-dielectric metamaterials

    DEFF Research Database (Denmark)

    Kuznetsova, S. M.; Andryieuski, Andrei; Lavrinenko, Andrei

    2015-01-01

    All-dielectric metamaterials consisting of high-dielectric inclusions in a low-dielectric matrix are considered as a low-loss alternative to resonant metal-based metamaterials. In this paper we investigate the applicability of the point electric and magnetic dipoles approximation to dielectric meta......-atoms on the example of a dielectric ring metamaterial. Despite the large electrical size of high-dielectric meta-atoms, the dipole approximation allows for accurate prediction of the metamaterials properties for the rings with diameters up to approximate to 0.8 of the lattice constant. The results provide important...... guidelines for design and optimization of all-dielectric metamaterials....

  12. The color dielectric model of QCD

    International Nuclear Information System (INIS)

    Pirner, H.-J.; Massachusetts Inst. of Tech., Cambridge, MA; Massachusetts Inst. of Tech., Cambridge, MA

    1992-01-01

    This paper demonstrates the emergence of valence gluons and their bound states, the glueballs from perturbative quantum chromodynamics (QCD). We discuss the phenomenological constraints and theoretical method needed to generate effective glueballs actions. We show how color dielectric confinement works naively and in the lattice model of color dielectrics. This lattice model is derived for SU(2) color by a blockspinning Monte Carlo renormalization group procedure. We interpret the resulting long-distance as a strongly interacting lattice string theory where the valence link gluon fields randomize in the color dielectric background which mimics the integrated out high-frequency gluon modes in the vacuum. The fluctuations of the color dielectric fields are related to color neutral glueballs modes. We give the extension of this color dielectric SU(2) theory for general SU(N) with quarks and address the problems associated with combining confinement and chiral symmetry breaking. Finally we prove the efficiency of the effective theory in applications to the heavy quark system, the the baryon, to the nucleon-nucleon interaction, to baryon models and the gluon plasma transition. In all those cases the behavior of the higher energy gluons can be monitored via the color dielectric fields. An increase in the energy density from ''deconfining'' the higher frequency modes inside the flux tube or in thermally excited matter shows up as an increase in the value of the color dielectric field and its associated energy density. (Author)

  13. Analysis of electron interactions in dielectric gases

    International Nuclear Information System (INIS)

    Olivet, Aurelio; Duque, Daniel; Vega, Lourdes F.

    2007-01-01

    We present and discuss results concerning electron interactions processes of dielectric gases and their relationship with the macroscopic behavior of these gases, in particular, with their dielectric strength. Such analysis is based on calculating energies of reactions for molecular ionization, dissociative ionization, parent negative ion formation, and dissociative electron attachment processes. We hypothesize that the estimation of the required energy for a reduced number of processes that take place in electrically stressed gases could be related to the gas' capability to manage the electron flow during an electrical discharge. All calculations were done with semiempirical quantum chemistry methods, including an initial optimization of molecular geometry and heat of formation of the dielectric gases and all of species that appear during electron interaction reactions. The performance of semiempirical methods Austin model 1 and Parametric model 3 (PM3) was compared for several compounds, PM3 being superior in most cases. Calculations performed for a sample of nine dielectric gases show that electron attachment and detachment processes occur in different energy bands that do not overlap for any value of the dielectric strength. We have also analyzed the relationship between dielectric strength and two physical properties: electron affinity and ionization energy. Calculations performed for 43 dielectric gases show no clear correlation between them, although certain guidelines for the qualitative estimation of dielectric strength can still be assessed

  14. The dipole moment of a wall-charged void in a bulk dielectric

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson

    1993-01-01

    The dipole moment of a wall-charged void is examined with reference to the spatial extent of the surface charge density σ and the distribution of this charge. The salient factors influencing the void dipole moment are also examined. From a study of spherical voids, it is shown that, although the σ......-distribution influences the dipole moment, the spatial extent of σ has a greater influence. This behavior is not unexpected. For a void of fixed dimensions, the smaller the charged surface area, the greater is the charges, and thus the greater the dipole moment...

  15. PREFACE: Dielectrics 2009: Measurement Analysis and Applications

    Science.gov (United States)

    Vaughan, Alun; Williams, Graham

    2009-07-01

    The conference Dielectrics 2009: Measurements, Analysis and Applications represents a significant milestone in the evolution of dielectrics research in the UK. It is reasonable to state that the academic study of dielectrics has led to many fundamental advances and that dielectric materials underpin the modern world in devices ranging from field effect transistors, which operate at extremely high fields, albeit low voltages, to the high voltage plants that provide the energy that powers our economy. The origins of the Dielectrics Group of the Institute of Physics (IOP), which organized this conference, can be traced directly back to the early 1960s, when Professor Mansel Davies was conducting research into the dielectric relaxation behaviour of polar liquids and solids at The Edward Davies Chemical Laboratories of the University College of Wales, Aberystwyth. He was already well-known internationally for his studies of molecular structure and bonding of small molecules, using infra-red-spectroscopy, and of the physical properties of hydrogen-bonded liquids and solids, using thermodynamic methods. Dielectric spectroscopy was a fairly new area for him and he realized that opportunities for scientists in the UK to gather together and discuss their research in this developing area of physical chemistry/chemical physics were very limited. He conceived the idea of forming a Dielectrics Discussion Group (DDG), which would act as a meeting point and provide a platform for dielectrics research in the UK and beyond and, as a result, a two-day Meeting was convened in the spring of 1968 at Gregynog Hall of the University of Wales, near Newtown, Montgomeryshire. It was organized by Mansel Davies, Alun Price and Graham Williams, all physical chemists from the UCW, Aberystwyth. Fifty scientists attended, being a mix of physical chemists, theoretical chemists, physicists, electrical engineers, polymer and materials scientists, all from the UK, except Dr Brendan Scaife of Trinity

  16. Identification of microscopic domain wall motion from temperature dependence of nonlinear dielectric response.

    Czech Academy of Sciences Publication Activity Database

    Mokrý, Pavel; Sluka, T.

    2017-01-01

    Roč. 110, č. 16 (2017), č. článku 162906. ISSN 0003-6951 R&D Projects: GA ČR(CZ) GA14-32228S Institutional support: RVO:61389021 Keywords : microscopic domain wall * electric fields * temperature dependence Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering OBOR OECD: Electrical and electronic engineering Impact factor: 3.411, year: 2016 http://dx.doi.org/10.1063/1.4981874

  17. Charge accumulation in lossy dielectrics: a review

    DEFF Research Database (Denmark)

    Rasmussen, Jørgen Knøster; McAllister, Iain Wilson; Crichton, George C

    1999-01-01

    At present, the phenomenon of charge accumulation in solid dielectrics is under intense experimental study. Using a field theoretical approach, we review the basis for charge accumulation in lossy dielectrics. Thereafter, this macroscopic approach is applied to planar geometries such that the mat......At present, the phenomenon of charge accumulation in solid dielectrics is under intense experimental study. Using a field theoretical approach, we review the basis for charge accumulation in lossy dielectrics. Thereafter, this macroscopic approach is applied to planar geometries...

  18. Slot-coupled CW standing wave accelerating cavity

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shaoheng; Rimmer, Robert; Wang, Haipeng

    2017-05-16

    A slot-coupled CW standing wave multi-cell accelerating cavity. To achieve high efficiency graded beta acceleration, each cell in the multi-cell cavity may include different cell lengths. Alternatively, to achieve high efficiency with acceleration for particles with beta equal to 1, each cell in the multi-cell cavity may include the same cell design. Coupling between the cells is achieved with a plurality of axially aligned kidney-shaped slots on the wall between cells. The slot-coupling method makes the design very compact. The shape of the cell, including the slots and the cone, are optimized to maximize the power efficiency and minimize the peak power density on the surface. The slots are non-resonant, thereby enabling shorter slots and less power loss.

  19. Dielectric Properties of Flocculated Water-in-Oil Emulsions

    Energy Technology Data Exchange (ETDEWEB)

    Skodvin, T.

    1995-12-31

    When an offshore oil field is near completion, water occupies a large fraction of the available pore volume. Thus, in collecting the oil and gas reserves, one has to deal with a high co-production of either formation- or injected water. This doctoral thesis focuses on the effect of water-in-oil emulsions on the dielectric properties, in particular the effect of flocculation. Various dielectric models are applied to obtain methods for qualitative and quantitative characterization of the flocculated state. Permittivity and measurement of dielectric properties are discussed as a basis for the interpretation of the dielectric properties of the emulsions. Various flocculation models are presented. It is concluded that the dielectric properties of water-in-oil emulsions are strongly influenced by continuously ongoing processes in the system. Because of flocculation and sedimentation the traditional dielectric mixture models cannot satisfactorily predict the dielectric behaviour. The experimentally obtained permittivities for the emulsions can be reproduced by including flocculation in the models and treating the floc aggregates as spheroids or subsystems with dielectric properties given by the degree of flocculation. The models discussed have difficulties reproducing the complete frequency behaviour found experimentally. This is probably because the dielectric relaxation may be influenced by processes not included in the models, such as the effects of dipolar or multipolar interactions between the droplets. For further research it is recommended that rheological and dielectric measurements be combined. 227 refs., 61 figs., 16 tabs.

  20. Dielectric Properties of Flocculated Water-in-Oil Emulsions

    Energy Technology Data Exchange (ETDEWEB)

    Skodvin, T

    1996-12-31

    When an offshore oil field is near completion, water occupies a large fraction of the available pore volume. Thus, in collecting the oil and gas reserves, one has to deal with a high co-production of either formation- or injected water. This doctoral thesis focuses on the effect of water-in-oil emulsions on the dielectric properties, in particular the effect of flocculation. Various dielectric models are applied to obtain methods for qualitative and quantitative characterization of the flocculated state. Permittivity and measurement of dielectric properties are discussed as a basis for the interpretation of the dielectric properties of the emulsions. Various flocculation models are presented. It is concluded that the dielectric properties of water-in-oil emulsions are strongly influenced by continuously ongoing processes in the system. Because of flocculation and sedimentation the traditional dielectric mixture models cannot satisfactorily predict the dielectric behaviour. The experimentally obtained permittivities for the emulsions can be reproduced by including flocculation in the models and treating the floc aggregates as spheroids or subsystems with dielectric properties given by the degree of flocculation. The models discussed have difficulties reproducing the complete frequency behaviour found experimentally. This is probably because the dielectric relaxation may be influenced by processes not included in the models, such as the effects of dipolar or multipolar interactions between the droplets. For further research it is recommended that rheological and dielectric measurements be combined. 227 refs., 61 figs., 16 tabs.

  1. High thermal conductivity lossy dielectric using a multi layer configuration

    Science.gov (United States)

    Tiegs, Terry N.; Kiggans, Jr., James O.

    2003-01-01

    Systems and methods are described for loss dielectrics. A loss dielectric includes at least one high dielectric loss layer and at least one high thermal conductivity-electrically insulating layer adjacent the at least one high dielectric loss layer. A method of manufacturing a loss dielectric includes providing at least one high dielectric loss layer and providing at least one high thermal conductivity-electrically insulating layer adjacent the at least one high dielectric loss layer. The systems and methods provide advantages because the loss dielectrics are less costly and more environmentally friendly than the available alternatives.

  2. Electrical actuation of dielectric droplets

    International Nuclear Information System (INIS)

    Kumari, N; Bahadur, V; Garimella, S V

    2008-01-01

    Electrical actuation of liquid droplets at the microscale offers promising applications in the fields of microfluidics and lab-on-a-chip devices. Much prior research has targeted the electrical actuation of electrically conducting liquid droplets; however, the actuation of dielectric droplets has remained relatively unexplored, despite the advantages associated with the use of a dielectric droplet. This paper presents modeling and experimental results on the electrical actuation of dielectric droplets between two flat plates. A first-order analytical model, based on the energy-minimization principle, is developed to estimate the electrical actuation force on a dielectric droplet as it moves between two flat plates. Two versions of this analytical model are benchmarked for their suitability and accuracy against a detailed numerical model. The actuation force prediction is then combined with available semi-analytical expressions for predicting the forces opposing droplet motion to develop a model that predicts transient droplet motion under electrical actuation. Electrical actuation of dielectric droplets is experimentally demonstrated by moving transformer oil droplets between two flat plates under the influence of an actuation voltage. Droplet velocities and their dependence on the plate spacing and the applied voltage are experimentally measured and showed reasonable agreement with predictions from the models developed

  3. Trends of microwave dielectric materials for antenna application

    International Nuclear Information System (INIS)

    Sulong, T. A. T.; Osman, R. A. M.; Idris, M. S.

    2016-01-01

    Rapid development of a modern microwave communication system requires a high quality microwave dielectric ceramic material to be used as mobile and satellite communication. High permittivity of dielectric ceramics leads to fabrication of compact device for electronic components. Dielectric ceramics which used for microwave applications required three important parameters such as high or appropriate permittivity (ε_r), high quality factor (Q _f ≥ 5000 GH z) and good temperature coefficient of resonant frequency (τ_f). This paper review of various dielectric ceramic materials used as microwave dielectric materials and related parameters for antenna applications.

  4. Public Dose Assessment Modeling from Skyshine by Proton Accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Mwambinga, S. A. [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Yoo, S. J. [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2013-10-15

    In this paper, the skyshine dose by proton accelerator (230 MeV) has been evaluated. The amount of dose by skyshine is related to some influence factors which are emission angle (Height wall), the thickness of ceiling and distance from source to receptor (Human body). Empirical formula is made by using MCNPX code results. It can easily calculate and assess dose from skyshine by proton accelerator. The skyshine doses are calculated with MCNPX code and DCFs in ICRP 116. Thereafter, we made empirical formula which can calculate dose easily and be compared with the results of MCNPX. The maximum exposure point by skyshine is about 5 ∼ 10 m from source. Therefore, the licensee who wants to operate the proton accelerator must keep the appropriate distance from accelerator and set the fence to restrict the approach by the public. And, exposure doses by accelerator depend on operating time and proton beam intensities. Eq. (6) suggested in this study is just considered for mono energy proton accelerator. Therefore, it is necessary to expand the dose calculation to diverse proton energies. Radiations like neutron and photon generated by high energy proton accelerators over 10 MeV, are important exposure sources to be monitored to radiation workers and the public members near the facility. At that case, one of the exposure pathways to the public who are located in near the facility is skyshine. Neutrons and photons can be scattered by the atmosphere near the facility and exposed to public as scattered dose. All of the facilities using high energy radiation and NDI (Non-Destructive Inspection) which is tested at open field, skyshine dose must be taken into consideration. Skyshine dose is not related to the wall thickness of radiation shielding directly.

  5. Effect of manganese doping of BaSrTiO{sub 3} on diffusion and domain wall pinning

    Energy Technology Data Exchange (ETDEWEB)

    Nadaud, Kevin, E-mail: kevin.nadaud@etu.univ-nantes.fr; Borderon, Caroline, E-mail: caroline.borderon@univ-nantes.fr; Renoud, Raphaël; Gundel, Hartmut W. [IETR, UMR CNRS 6164, University of Nantes, Nantes (France)

    2015-02-28

    In the present paper, the influence of manganese doping on the dielectric properties of BaSrTiO{sub 3} thin films is presented. The real and imaginary parts of the material's permittivity have been measured in a large frequency range (100 Hz–1 MHz) and as a function of the electric field. The tunability and the figure of merit of the material have been obtained from the measurement of the permittivity under an applied DC bias electric field. For the undoped material, the dielectric losses become important for a large DC bias which leads to breakdown. At a suitable dopant rate, this effect disappears. In order to better understand the origin of the related phenomena, we measure the permittivity as a function of the AC excitation amplitude and we decompose the obtained permittivity with the hyperbolic law. This enables to extract the different contributions of the bulk (low frequency diffusion and high frequency lattice relaxation) and of the domain wall motions (vibration and pinning/unpinning) to the material's dielectric permittivity and to understand the effect of manganese doping on each contribution. Knowledge of the related mechanisms allows us to establish the optimum dopant rate (mainly conditioned by the lattice contribution) and to reduce the domain wall motion, which finally is beneficial for the desired properties of the ferroelectric thin film. A particular attention is paid to low frequency diffusion, an especially harmful effect when a DC biasing is mandatory (tunable electronic component in mobile telecommunication devices for example)

  6. AN OVERVIEW OF HIGH VOLTAGE DIELECTRIC MATERIAL FOR TRAVELING WAVE KICKER MAGNET APPLICATION

    International Nuclear Information System (INIS)

    ZHANG, W.; SANDBERG, J.; TUOZZOLO, J.; CASSEL, R.; DUCIMETIERE, L.; JENSEN, C.; BARNES, M.; WAIT, G.; WANG, J.

    2002-01-01

    Pulsed high power fast kickers are being used to change beam trajectories in particle accelerators. The fast rise and fall time of pulse waveform demands a transmission line structure for the kicker deflector design. The ideal design will be parallel metal plates. However, it uses very long straight sections to achieve the required deflection. In accelerators with constrained straight sections, high permeability materials such as ferrite have to be used to gain deflection efficiency. The transmission line kicker magnet is also referred as traveling wave kicker magnet. Its construction is based on distributed 1-C cells along the longitudinal direction. The magnetic cells and capacitive cells are interleaved to simulate the characteristic impedance of a transmission line to minimize pulse reflection, and provide adequate frequency bandwidth to transmit the kicker pulse with fast rise and fall time. The magnetic cells are usually made of ferrite ceramics, but the capacitive cells have been made with different materials. For traveling wave kickers with higher impedance, the parallel plate vacuum capacitor has been used in CERN and KEK design. Others have used ceramic capacitors, printed circuit boards, and high permittivity ceramics as the capacitive cell. The high dielectric material has the advantage of compactness for low impedance kicker magnet construction. It continues to be very attractive for future kicker magnet applications. The high voltage phenomena associated with high dielectric ceramic materials have been widely reported in many industrial application areas. Their implication in the traveling wave magnet application has to be well understood. In this presentation, the areas requiring further quantitative study will be outlined

  7. High-efficient light absorption of monolayer graphene via cylindrical dielectric arrays and the sensing application

    Science.gov (United States)

    Zhou, Peng; Zheng, Gaige

    2018-04-01

    The efficiency of graphene-based optoelectronic devices is typically limited by the poor absolute absorption of light. A hybrid structure of monolayer graphene with cylindrical titanium dioxide (TiO2) array and aluminum oxide (Al2O3) spacer layer on aluminum (Al) substrate has been proposed to enhance the absorption for two-dimensional (2D) materials. By combining dielectric array with metal substrate, the structure achieves multiple absorption peaks with near unity absorbance at near-infrared wavelengths due to the resonant effect of dielectric array. Completed monolayer graphene is utilized in the design without any demand of manufacture process to form the periodic patterns. Further analysis indicates that the near-field enhancement induced by surface modes gives rise to the high absorption. This favorable field enhancement and tunability of absorption not only open up new approaches to accelerate the light-graphene interaction, but also show great potential for practical applications in high-performance optoelectronic devices, such as modulators and sensors.

  8. Dielectric spectroscopy of watermelons for quality sensing

    Science.gov (United States)

    Nelson, Stuart O.; Guo, Wen-chuan; Trabelsi, Samir; Kays, Stanley J.

    2007-07-01

    Dielectric properties of four small-sized watermelon cultivars, grown and harvested to provide a range of maturities, were measured with an open-ended coaxial-line probe and an impedance analyser over the frequency range from 10 MHz to 1.8 GHz. Probe measurements were made on the external surface of the melons and also on tissue samples from the edible internal tissue. Moisture content and soluble solids content (SSC) were measured for internal tissue samples, and SSC (sweetness) was used as the quality factor for correlation with the dielectric properties. Individual dielectric constant and loss factor correlations with SSC were low, but a high correlation was obtained between the SSC and permittivity from a complex-plane plot of dielectric constant and loss factor, each divided by SSC. However, SSC prediction from the dielectric properties by this relationship was not as high as expected (coefficient of determination about 0.4). Permittivity data (dielectric constant and loss factor) for the melons are presented graphically to show their relationships with frequency for the four melon cultivars and for external surface and internal tissue measurements. A dielectric relaxation for the external surface measurements, which may be attributable to a combination of bound water, Maxwell-Wagner, molecular cluster or ion-related effects, is also illustrated. Coefficients of determination for complex-plane plots, moisture content and SSC relationship, and penetration depth are also shown graphically. Further studies are needed for determining the practicality of sensing melon quality from their dielectric properties.

  9. The Dielectric Constant of Lubrication Oils

    National Research Council Canada - National Science Library

    Carey, A

    1998-01-01

    The values of the dielectric constant of simple molecules is discussed first, along with the relationship between the dielectric constant and other physical properties such as boiling point, melting...

  10. Method for fabrication of crack-free ceramic dielectric films

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Beihai; Narayanan, Manoj; Balachandran, Uthamalingam; Chao, Sheng; Liu, Shanshan

    2017-12-05

    The invention provides a process for forming crack-free dielectric films on a substrate. The process comprises the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. The process provides a thick crack-free dielectric film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.

  11. Method for fabrication of crack-free ceramic dielectric films

    Science.gov (United States)

    Ma, Beihai; Balachandran, Uthamalingam; Chao, Sheng; Liu, Shanshan; Narayanan, Manoj

    2014-02-11

    The invention provides a process for forming crack-free dielectric films on a substrate. The process comprise the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. Also provided was a thick crack-free dielectric film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.

  12. Optimization of silver-dielectric-silver nanoshell for sensing applications

    International Nuclear Information System (INIS)

    Shirzaditabar, Farzad; Saliminasab, Maryam

    2013-01-01

    In this paper, resonance light scattering (RLS) properties of a silver-dielectric-silver nanoshell, based on quasi-static approach and plasmon hybridization theory, are investigated. Scattering spectrum of silver-dielectric-silver nanoshell has two intense and clearly separated RLS peaks and provides a potential for biosensing based on surface plasmon resonance and surface-enhanced Raman scattering. The two RLS peaks in silver-dielectric-silver nanoshell are optimized by tuning the geometrical dimensions. In addition, the optimal geometry is discussed to obtain the high sensitivity of silver-dielectric-silver nanoshell. As the silver core radius increases, the sensitivity of silver-dielectric-silver nanoshell decreases whereas increasing the middle dielectric thickness increases the sensitivity of silver-dielectric-silver nanoshell

  13. Polaron-electron assisted giant dielectric dispersion in SrZrO{sub 3} high-k dielectric

    Energy Technology Data Exchange (ETDEWEB)

    Borkar, Hitesh; Barvat, Arun; Pal, Prabir; Kumar, Ashok, E-mail: ashok553@nplindia.org [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-National Physical Laboratory (CSIR-NPL) Campus, Dr. K S Krishnan Marg, New Delhi 110012 (India); Shukla, A. K. [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Pulikkotil, J. J. [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-National Physical Laboratory (CSIR-NPL) Campus, Dr. K S Krishnan Marg, New Delhi 110012 (India); Computation and Networking Facility, CSIR-National Physical Laboratory, New Delhi 110012 (India)

    2016-06-07

    The SrZrO{sub 3} is a well known high-k dielectric constant (∼22) and high optical bandgap (∼5.8 eV) material and one of the potential candidates for future generation nanoelectronic logic elements (8 nm node technology) beyond silicon. Its dielectric behavior is fairly robust and frequency independent till 470 K; however, it suffers a strong small-polaron based electronic phase transition (T{sub e}) linking 650 to 750 K. The impedance spectroscopy measurements revealed the presence of conducting grains and grain boundaries at elevated temperature which provide energetic mobile charge carriers with activation energy in the range of 0.7 to 1.2 eV supporting the oxygen ions and proton conduction. X-ray photoemission spectroscopy measurements suggest the presence of weak non-stoichiometric O{sup 2−} anions and hydroxyl species bound to different sites at the surface and bulk. These thermally activated charge carriers at elevated temperature significantly contribute to the polaronic based dielectric anomaly and conductivity. Our dielectric anomaly supports pseudo phase transition due to high degree of change in ZrO{sub 6} octahedral angle in the temperature range of 650–750 K, where electron density and phonon vibration affect the dielectric and conductivity properties.

  14. The measurement of the dielectric constant of concrete pipes and clay pipes

    Science.gov (United States)

    McGraw, David

    To optimize the effectiveness of the rehabilitation of underground utilities, taking in consideration limitation of available resources, there is a need for a cost effective and efficient sensing systems capable of providing effective, in real time and in situ, measurement of infrastructural characteristics. To carry out accurate non-destructive condition assessment of buried and above ground infrastructure such as sewers, bridges, pavements and dams, an advanced ultra-wideband (UWB) based radar was developed at Trenchless Technology Centre (TTC) and Centre for Applied Physics Studies (CAPS) at Louisiana Tech University (LTU). One of the major issues in designing the FCC compliant UWB radar was the contribution of the pipe wall, presence of complex soil types and moderate-to-high moisture levels on penetration depth of the electromagnetic (EM) energy. The electrical properties of the materials involved in designing the UWB radar exhibit a significant variation as a result of the moisture content, mineral content, bulk density, temperature and frequency of the electromagnetic signal propagating through it. Since no measurements of frequency dependence of the dielectric permittivity and conductivities of the pipe wall material in the FCC approved frequency range exist, in this thesis, the dielectric constant of concrete and clay pipes are measured over a microwave frequency range from 1 Ghz to 10 Ghz including the effects of moisture and chloride content. A high performance software package called MU-EPSLN(TM) was used for the calculations. Data reduction routines to calculate the complex permeability and permittivity of materials as well as other parameters are also provided. The results obtained in this work will be used to improve the accuracy of the numerical simulations and the performances of the UWB radar system.

  15. Trends of microwave dielectric materials for antenna application

    Energy Technology Data Exchange (ETDEWEB)

    Sulong, T. A. T., E-mail: tuanamirahtuansulong@gmail.com; Osman, R. A. M., E-mail: rozana@unimap.edu.my [School of Microelectronic Engineering, Universiti Malaysia Perlis, Pauh Putra Campus, 02600 Arau, Perlis (Malaysia); Idris, M. S., E-mail: sobri@unimap.edu.my [Sustainable Engineering Research Cluster, School of Material Engineering, Universiti Malaysia Perlis, Blok B, Taman Pertiwi Indah, Seriab, 01000 Kangar, Perlis (Malaysia)

    2016-07-19

    Rapid development of a modern microwave communication system requires a high quality microwave dielectric ceramic material to be used as mobile and satellite communication. High permittivity of dielectric ceramics leads to fabrication of compact device for electronic components. Dielectric ceramics which used for microwave applications required three important parameters such as high or appropriate permittivity (ε{sub r}), high quality factor (Q {sub f} ≥ 5000 GH z) and good temperature coefficient of resonant frequency (τ{sub f}). This paper review of various dielectric ceramic materials used as microwave dielectric materials and related parameters for antenna applications.

  16. Dielectric properties of agricultural materials and their applications

    CERN Document Server

    Nelson, Stuart

    2015-01-01

    Dielectric Properties of Agricultural Materials and Their Applications provides an understanding of the fundamental principles governing dielectric properties of materials, describes methods for measuring such properties, and discusses many applications explored for solving industry problems. The information in this reference stimulates new research for solving problems associated with production, handling, and processing of agricultural and food products. Anyone seeking a better understanding of dielectric properties of materials and application of radio-frequency and microwave electromagnetic energy for solution of problems in agriculture and related fields will find this an essential resource. Presents applications of dielectric properties for sensing moisture in grain and seed and the use of such properties in radio-frequency and microwave dielectric heating of agricultural materials Offers information for finding correlations between dielectric properties and quality attributes such as sweetness in melon...

  17. Evaluation of high temperature capacitor dielectrics

    Science.gov (United States)

    Hammoud, Ahmad N.; Myers, Ira T.

    1992-01-01

    Experiments were carried out to evaluate four candidate materials for high temperature capacitor dielectric applications. The materials investigated were polybenzimidazole polymer and three aramid papers: Voltex 450, Nomex 410, and Nomex M 418, an aramid paper containing 50 percent mica. The samples were heat treated for six hours at 60 C and the direct current and 60 Hz alternating current breakdown voltages of both dry and impregnated samples were obtained in a temperature range of 20 to 250 C. The samples were also characterized in terms of their dielectric constant, dielectric loss, and conductivity over this temperature range with an electrical stress of 60 Hz, 50 V/mil present. Additional measurements are underway to determine the volume resistivity, thermal shrinkage, and weight loss of the materials. Preliminary data indicate that the heat treatment of the films slightly improves the dielectric properties with no influence on their breakdown behavior. Impregnation of the samples leads to significant increases in both alternating and direct current breakdown strength. The results are discussed and conclusions made concerning their suitability as high temperature capacitor dielectrics.

  18. Development of pipe wall thinning prediction software 'FALSET'

    International Nuclear Information System (INIS)

    Yoneda, Kimitoshi; Morita, Ryo; Inada, Fumio; Fujiwara, Kazutoshi

    2012-01-01

    Pipe wall thinning in power plants has been managed for maintaining plant integrity and safety with great importance. The target thinning phenomena are Flow Accelerated Corrosion (FAC) and Liquid Droplet Impingement Erosion (LDI). At present, the management is based on thinning rate and residual lifetime evaluation using pipe wall thickness measurement results. For the future, more safety and improvement in the management is required, and in this sense, prediction method of wall thinning is willing to be introduced. Therefore, prediction model of FAC and LDI have been constructed in CRIEPI, and to utilize these models to actual plant piping management easily, prediction software 'FALSET' is developed. FALSET has equipped with essential function for pipe wall thinning management in power plants, as follows; (1) Information and condition input of plant piping system and its component, (2) Wall thinning rate evaluation with CRIEPI's FAC/LDI prediction model, (3) Loading of wall thickness measurement data files and graphics of data trend, (4) Residual lifetime evaluation considering both measured and predicted thinning rate, (5) Statistical process and graphics of thinning rate and residual lifetime for multi-piping systems. With further verification and improvement of each function, there will be a perspective for this FALSET to be utilized as a management tool in power plants. (author)

  19. Discharge ignition near a dielectric

    NARCIS (Netherlands)

    Sobota, A.; Veldhuizen, van E.M.; Stoffels, W.W.

    2008-01-01

    Electrical breakdown in noble gas near a dielectric is an important issue in lighting industry. In order to investigate the influence of the dielectric on the ignition process, we perform measurements in argon, with pressure varying from 0.1 to 1 bar, using a pin–pin electrode geometry. Here, we

  20. Passive multi-frequency brain imaging and hyperthermia irradiation apparatus: the use of dielectric matching materials in phantom experiments

    International Nuclear Information System (INIS)

    Gouzouasis, Ioannis; Karathanasis, Konstantinos; Karanasiou, Irene; Uzunoglu, Nikolaos

    2009-01-01

    In this paper a hybrid system able to provide focused microwave radiometry and deep brain hyperthermia is experimentally tested. The system's main module is an ellipsoidal conductive wall cavity which acts as a beam former, focusing the electromagnetic energy on the medium of interest. The system's microwave radiometry component has extensively been studied theoretically and experimentally in the past few years with promising results. In this work, further investigation concerning the improvement of the hybrid system's focusing properties is conducted. Specifically, microwave radiometry and hyperthermia experiments are performed using water phantoms surrounded by dielectric layers used as matching material to enhance detection/penetration depth and spatial resolution. The results showed that the dielectric material reduces the reflected electromagnetic energy on the air–phantom interface, resulting in improved temperature resolution and higher detection or penetration of the energy when microwave radiometry and hyperthermia are applied respectively

  1. Metamaterial Behavior of Polymer Nanocomposites Based on Polypropylene/Multi-Walled Carbon Nanotubes Fabricated by Means of Ultrasound-Assisted Extrusion

    Directory of Open Access Journals (Sweden)

    Juan C. Pérez-Medina

    2016-11-01

    Full Text Available Metamaterial behavior of polymer nanocomposites (NCs based on isotactic polypropylene (iPP and multi-walled carbon nanotubes (MWCNTs was investigated based on the observation of a negative dielectric constant (ε′. It is demonstrated that as the dielectric constant switches from negative to positive, the plasma frequency (ωp depends strongly on the ultrasound-assisted fabrication method, as well as on the melt flow index of the iPP. NCs were fabricated using ultrasound-assisted extrusion methods with 10 wt % loadings of MWCNTs in iPPs with different melt flow indices (MFI. AC electrical conductivity (σ(AC as a function of frequency was determined to complement the electrical classification of the NCs, which were previously designated as insulating (I, static-dissipative (SD, and conductive (C materials. It was found that the SD and C materials can also be classified as metamaterials (M. This type of behavior emerges from the negative dielectric constant observed at low frequencies although, at certain frequencies, the dielectric constant becomes positive. Our method of fabrication allows for the preparation of metamaterials with tunable ωp. iPP pure samples show only positive dielectric constants. Electrical conductivity increases in all cases with the addition of MWCNTs with the largest increases observed for samples with the highest MFI. A relationship between MFI and the fabrication method, with respect to electrical properties, is reported.

  2. Metamaterial Behavior of Polymer Nanocomposites Based on Polypropylene/Multi-Walled Carbon Nanotubes Fabricated by Means of Ultrasound-Assisted Extrusion

    Science.gov (United States)

    Pérez-Medina, Juan C.; Waldo-Mendoza, Miguel A.; Cruz-Delgado, Víctor J.; Quiñones-Jurado, Zoe V.; González-Morones, Pablo; Ziolo, Ronald F.; Martínez-Colunga, Juan G.; Soriano-Corral, Florentino; Avila-Orta, Carlos A.

    2016-01-01

    Metamaterial behavior of polymer nanocomposites (NCs) based on isotactic polypropylene (iPP) and multi-walled carbon nanotubes (MWCNTs) was investigated based on the observation of a negative dielectric constant (ε′). It is demonstrated that as the dielectric constant switches from negative to positive, the plasma frequency (ωp) depends strongly on the ultrasound-assisted fabrication method, as well as on the melt flow index of the iPP. NCs were fabricated using ultrasound-assisted extrusion methods with 10 wt % loadings of MWCNTs in iPPs with different melt flow indices (MFI). AC electrical conductivity (σ(AC)) as a function of frequency was determined to complement the electrical classification of the NCs, which were previously designated as insulating (I), static-dissipative (SD), and conductive (C) materials. It was found that the SD and C materials can also be classified as metamaterials (M). This type of behavior emerges from the negative dielectric constant observed at low frequencies although, at certain frequencies, the dielectric constant becomes positive. Our method of fabrication allows for the preparation of metamaterials with tunable ωp. iPP pure samples show only positive dielectric constants. Electrical conductivity increases in all cases with the addition of MWCNTs with the largest increases observed for samples with the highest MFI. A relationship between MFI and the fabrication method, with respect to electrical properties, is reported. PMID:28774042

  3. Thermally switchable dielectrics

    Science.gov (United States)

    Dirk, Shawn M.; Johnson, Ross S.

    2013-04-30

    Precursor polymers to conjugated polymers, such as poly(phenylene vinylene), poly(poly(thiophene vinylene), poly(aniline vinylene), and poly(pyrrole vinylene), can be used as thermally switchable capacitor dielectrics that fail at a specific temperature due to the non-conjugated precursor polymer irreversibly switching from an insulator to the conjugated polymer, which serves as a bleed resistor. The precursor polymer is a good dielectric until it reaches a specific temperature determined by the stability of the leaving groups. Conjugation of the polymer backbone at high temperature effectively disables the capacitor, providing a `built-in` safety mechanism for electronic devices.

  4. Breakdown of coupling dielectrics for Si microstrip detectors

    International Nuclear Information System (INIS)

    Candelori, A.; Paccagnella, A.; Padova Univ.; Saglimbeni, G.

    1999-01-01

    Double-layer coupling dielectrics for AC-coupled Si microstrip detectors have been electrically characterized in order to determine their performance in a radiation-harsh environment, with a focus on the dielectric breakdown. Two different dielectric technologies have been investigated: SiO 2 /TEOS and SiO 2 /Si 3 N 4 . Dielectrics have been tested by using a negative gate voltage ramp of 0.2 MV/(cm·s). The metal/insulator/Si I-V characteristics show different behaviours depending on the technology. The extrapolated values of the breakdown field for unirradiated devices are significantly higher for SiO 2 /Si 3 N 4 dielectrics, but the data dispersion is lower for SiO 2 /TEOS devices. No significant variation of the breakdown field has been measured after a 10 Mrad (Si) γ irradiation for SiO 2 /Si 3 N 4 dielectrics. Finally, the SiO 2 /Si 3 N 4 DC conduction is enhanced if a positive gate voltage ramp is applied with respect to the negative one, due to the asymmetric conduction of the double-layer dielectric

  5. Environmental impact assessment methods of the radiation generated by the runing medical linear accelerator

    International Nuclear Information System (INIS)

    Yin haihua; Yao Zhigang

    2014-01-01

    This article describes the environmental impact assessment methods of the radiation generated by the runing. medical linear accelerator. The material and thickness of shielding wall and protective doors of the linear accelerator were already knew, therefore we can evaluate the radiation by the runing. medical linear accelerator whether or not in the normal range of national standard by calculating the annual effective radiation dose of the surrounding personnel suffered. (authors)

  6. Capacitive Cells for Dielectric Constant Measurement

    Science.gov (United States)

    Aguilar, Horacio Munguía; Maldonado, Rigoberto Franco

    2015-01-01

    A simple capacitive cell for dielectric constant measurement in liquids is presented. As an illustrative application, the cell is used for measuring the degradation of overheated edible oil through the evaluation of their dielectric constant.

  7. Electrical characterization of microdischarges produced by dielectric barrier discharge in dry air at atmospheric pressure

    International Nuclear Information System (INIS)

    Jidenko, N; Petit, M; Borra, J P

    2006-01-01

    This work addresses the case of millimetre sized plane-to-plane dielectric barrier discharge with sinusoidal voltage between 1 and 60 kHz for different configurations in air at atmospheric pressure. The first aim of this work is to achieve a representative statistical analysis of the electrical characteristics of the microdischarges. The numerical data treatment presented here enables us to determine the maximum current, the duration, the amount of charge and the triggering voltage for each current pulse. Both the average values as well as the deviations are checked. The relative influence of the operating parameters (voltage, gas flow rate, gap width, frequency) on the local surface polarization, electron attachment and temperature affecting microdischarge characteristics has been depicted in different arrangements. A special attention is paid to the influence of dielectric walls inside the discharge gap, perpendicular to the electrodes. Besides, this study allows the identification of the operating conditions for which all the microdischarges can be considered identical to study the local physical and chemical processes around each microdischarge

  8. Electrical characterization of microdischarges produced by dielectric barrier discharge in dry air at atmospheric pressure

    Energy Technology Data Exchange (ETDEWEB)

    Jidenko, N [Laboratoire de Physique des Gaz et des Plasmas (CNRS-Universite Paris XI), Equipe Decharges Electriques et Environnement, Supelec, 91190 Gif sur Yvette (France); Petit, M [Service Electrotechnique et Electronique Industrielle, SUPELEC Plateau de Moulon, 91192 Gif sur Yvette Cedex (France); Borra, J P [Laboratoire de Physique des Gaz et des Plasmas (CNRS-Universite Paris XI), Equipe Decharges Electriques et Environnement, Supelec, 91190 Gif sur Yvette (France)

    2006-01-21

    This work addresses the case of millimetre sized plane-to-plane dielectric barrier discharge with sinusoidal voltage between 1 and 60 kHz for different configurations in air at atmospheric pressure. The first aim of this work is to achieve a representative statistical analysis of the electrical characteristics of the microdischarges. The numerical data treatment presented here enables us to determine the maximum current, the duration, the amount of charge and the triggering voltage for each current pulse. Both the average values as well as the deviations are checked. The relative influence of the operating parameters (voltage, gas flow rate, gap width, frequency) on the local surface polarization, electron attachment and temperature affecting microdischarge characteristics has been depicted in different arrangements. A special attention is paid to the influence of dielectric walls inside the discharge gap, perpendicular to the electrodes. Besides, this study allows the identification of the operating conditions for which all the microdischarges can be considered identical to study the local physical and chemical processes around each microdischarge.

  9. Intuitional experiment and numerical analysis of flow characteristics affected by flow accelerated corrosion in elbow pipe system

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyung Joon [School of Mechanical and Aerospace Engineering, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Kim, Kyung Hoon, E-mail: kimkh@khu.ac.kr [Department of Mechanical Engineering, Kyung Hee University, Seochun 1, Yongin, Gyeonggi 446-701 (Korea, Republic of)

    2016-05-15

    Highlights: • Wall-thinning erosion of pipelines in plants leads to fatal accidents unexpectedly. • Flow Acceleration Corrosion (FAC) is a main reason of wall-thinning. • For industrial safety, it is necessary to verify the tendency of FAC. • We focused on local wall thinning by FAC with intuitional visualization experiment and numerical analysis in elbow pipe.

  10. Norbornylene-based polymer systems for dielectric applications

    Science.gov (United States)

    Dirk, Shawn M [Albuquerque, NM; Wheeler, David R [Albuquerque, NM

    2012-07-17

    A capacitor having at least one electrode pair being separated by a dielectric component, with the dielectric component being made of a polymer such as a norbornylene-containing polymer with a dielectric constant greater than 3 and a dissipation factor less than 0.1 where the capacitor has an operating temperature greater than 100.degree. C. and less than 170.degree. C.

  11. A microwiggler Free-Electron Laser at the Brookhaven Accelerator Test Facility

    International Nuclear Information System (INIS)

    Batchelor, K.; Ben-Zvi, I.; Fernow, R.; Gallardo, J.; Kirk, H.; Pellegrini, C.; van Steenbergen, A.; Bhowmik, A.; Rockwell International Corp., Canoga Park, CA

    1989-01-01

    We report the design and status of an FEL experiment at the Brookhaven National Laboratory Accelerator Test Facility. A 50 MeV high brightness electron beam will be utilized for an oscillator experiment in the visible wavelength region. The microwiggler to be used is a superferric planar undulator with a 0.88 cm period, 60 cm length and K = 0.35. The optical cavity is a 368 cm long stable resonator with broadband dielectric coated mirrors. 8 refs., 2 figs., 4 tabs

  12. Implantation measurements to determine tritium permeation in first wall structures

    International Nuclear Information System (INIS)

    Holland, D.F.; Causey, R.A.

    1983-01-01

    A principal safety concern for a D-T burning fusion reactor is release of tritium during routine operation. Tritium implantation into first wall structures, and subsequent permeation into coolants, is potentially an important source of tritium loss. This paper reports on an experiment in which an ion accelerator was used to implant deuterium atoms in a stainless steel disk to simulate tritium implantation in first wall structures. The permeation rate was measured under various operating conditions. These results were used in the TMAP computer code to determine potential tritium loss rates for fusion reactors

  13. Implantation measurements to determine tritium permeation in first-wall structures

    International Nuclear Information System (INIS)

    Holland, D.F.; Causey, R.A.; Sattler, M.L.

    1983-01-01

    A principal safety concern for a D-T burning fusion reactor is release of tritium during routine operation. Tritium implantation into first-wall structures, and subsequent permeation into coolants, is potentially an important source of tritium loss. This paper reports on an experiment in which an ion accelerator was used to implant deuterium atoms in a stainless steel disk to simulate tritium implantation in first-wall structures. The permeation rate was measured under various operating conditions. These results were used in the TMAP computer code to determine potential tritium loss rates for fusion reactors

  14. Perfect coupling of light to a periodic dielectric/metal/dielectric structure

    Science.gov (United States)

    Wang, Zhengling; Li, Shiqiang; Chang, R. P. H.; Ketterson, John B.

    2014-07-01

    Using the finite difference time domain method, it is demonstrated that perfect coupling can be achieved between normally incident light and a periodic dielectric/metal/dielectric structure. The structure serves as a diffraction grating that excites modes related to the long range surface plasmon and short range surface plasmon modes that propagate on continuous metallic films. By optimizing the structural dimensions, perfect coupling is achieved between the incident light and these modes. A high Q of 697 and an accompanying ultrasharp linewidth of 0.8 nm are predicted for a 10 nm silver film for optimal conditions.

  15. Stray-electron accumulation and effects in HIF accelerators

    International Nuclear Information System (INIS)

    Cohen, R.H.; Friedman, A.; Furman, M.A.; Lund, S.M.; Molvik, A.W.; Stoltz, P.; Vay, J.-L.

    2003-01-01

    Stray electrons can be introduced in positive-charge accelerators for heavy ion fusion (or other applications) as a result of ionization of ambient gas or gas released from walls due to halo-ion impact, or as a result of secondary-electron emission. Electron accumulation is impacted by the ion beam potential, accelerating fields, multipole magnetic fields used for beam focus, and the pulse duration. We highlight the distinguishing features of heavy-ion accelerators as they relate to stray-electron issues, and present first results from a sequence of simulations to characterize the electron cloud that follows from realistic ion distributions. Also, we present ion simulations with prescribed random electron distributions, undertaken to begin to quantify the effects of electrons on ion beam quality

  16. Influence of Wall-Current-Compensation and Secondary-Electron-Emission on the Plasma Parameters and on the Performance of Electron Cyclotron Resonance Ion Sources

    International Nuclear Information System (INIS)

    Schachter, L.; Dobrescu, S.; Stiebing, K.E.

    2005-01-01

    Axial and radial diffusion processes determine the confinement time in an ECRIS. It has been demonstrated that a biased disk redirects the ion- and electron currents in the source in such a way that the source performance is improved. This effect is due to a partial cancellation of the compensating currents in the conductive walls of the plasma chamber.In this contribution we present an experiment, where these currents were effectively suppressed by using a metal-dielectric (MD) disk instead of the standard metallic disk in the Frankfurt 14-GHz-ECRIS. Lower values of the plasma potential and higher average charge states in the presence of the MD disk as compared to the case of the standard disk indicate that, due to the insulating properties of its dielectric layer the MD disk obviously blocks compensating wall currents better than applying bias to the metallic standard disk.A comparison with results from experiments with a MD liner in the source, covering essentially the complete radial walls of the plasma chamber, clearly demonstrates that the beneficial effect of the liner on the performance of the ECRIS is much stronger than that observed with the MD-disk. In accord with our earlier interpretation, it has to be concluded that the 'liner-effect' is not just the effect of blocking the compensating wall currents but rather has to be ascribed to the unique property of the thin MD liner as a strong secondary electron emitter under bombardment by charged particles

  17. Architecture of petawatt-class z-pinch accelerators

    International Nuclear Information System (INIS)

    Stygar, William A.; Mazarakis, Michael Gerrassimos; Cuneo, Michael Edward; Leeper, Ramon Joe; Ives, H.C.; Headley, D.I.; Wagoner, Tim C.; Porter, John Larry Jr.

    2006-01-01

    We have developed an accelerator architecture that can serve as the basis of the design of petawatt-class z-pinch drivers. The architecture has been applied to the design of two z-pinch accelerators, each of which can be contained within a 104-m-diameter cylindrical tank. One accelerator is driven by slow (∼1 (micro)s) Marx generators, which are a mature technology but which necessitate significant pulse compression to achieve the short pulses ( 4 capacitors, store 98 MJ, and erect to 5 MV; (ii) 600 water-dielectric triplate intermediate-store transmission lines, which also serve as pulse-forming lines; (iii) 600 5-MV laser-triggered gas switches; (iv) three monolithic radial-transmission-line impedance transformers, with triplate geometries and exponential impedance profiles; (v) a 6-level 5.5-m-diameter 15-MV vacuum insulator stack; (vi) six magnetically insulated vacuum transmission lines (MITLs); and (vii) a triple-post-hole vacuum convolute that adds the output currents of the six MITLs, and delivers the combined current to a z-pinch load. The accelerator delivers an effective peak current of 52 MA to a 10-mm-length z pinch that implodes in 95 ns, and 57 MA to a pinch that implodes in 120 ns. The LTD-driven accelerator includes monolithic radial transformers and a MITL system similar to those described above, but does not include intermediate-store transmission lines, multimegavolt gas switches, or a laser trigger system. Instead, this accelerator is driven by 210 LTD modules that include a total of 1 x 10 6 capacitors and 5 x 10 5 200-kV electrically triggered gas switches. The LTD accelerator stores 182 MJ and produces a peak electrical power of 1000 TW. The accelerator delivers an effective peak current of 68 MA to a pinch that implodes in 95 ns, and 75 MA to a pinch that implodes in 120 ns. Conceptually straightforward upgrades to these designs would deliver even higher pinch currents and faster implosions

  18. Tank wall thinning -- Process and programs

    International Nuclear Information System (INIS)

    Greer, S.D.; McBrine, W.J.

    1994-01-01

    In-service thinning of tank walls has occurred in the power industry and can pose a significant risk to plant safety and dependability. Appropriate respect for the energy stored in a high-pressure drain tank warrants a careful consideration of this possibility and appropriate action in order to assure the adequate safety margins against leakage or rupture. Although it has not proven to be a widespread problem, several cases of wall thinning and at least one recent tank rupture has highlighted this issue in recent years, particularly in nuclear power plants. However, the problem is not new or unique to the nuclear power industry. Severe wall thinning in deaerator tanks has been frequently identified at fossil-fueled power plants. There are many mechanisms which can contribute to tank wall thinning. Considerations for a specific tank are dictated by the system operating conditions, tank geometry, and construction material. Thinning mechanisms which have been identified include: Erosion/Corrosion Impingement Erosion Cavitation Erosion General Corrosion Galvanic Corrosion Microbial-induced Corrosion of course there are many other possible types of material degradation, many of which are characterized by pitting and cracking. This paper specifically addresses wall thinning induced by Erosion/Corrosion (also called Flow-Accelerated Corrosion) and Impingement Erosion of tanks in a power plant steam cycle. Many of the considerations presented are applicable to other types of vessels, such as moisture separators and heat exchangers

  19. Hysteresis behaviour of low-voltage organic field-effect transistors employing high dielectric constant polymer gate dielectrics

    International Nuclear Information System (INIS)

    Kim, Se Hyun; Yun, Won Min; Kwon, Oh-Kwan; Hong, Kipyo; Yang, Chanwoo; Park, Chan Eon; Choi, Woon-Seop

    2010-01-01

    Here, we report on the fabrication of low-voltage-operating pentacene-based organic field-effect transistors (OFETs) that utilize crosslinked cyanoethylated poly(vinyl alcohol) (CR-V) gate dielectrics. The crosslinked CR-V-based OFET could be operated successfully at low voltages (below 4 V), but abnormal behaviour during device operation, such as uncertainty in the field-effect mobility (μ) and hysteresis, was induced by the slow polarization of moieties embedded in the gate dielectric (e.g. polar functionalities, ionic impurities, water and solvent molecules). In an effort to improve the stability of OFET operation, we measured the dependence of μ and hysteresis on dielectric thickness, CR-V crosslinking conditions and sweep rate of the gate bias. The influence of the CR-V surface properties on μ, hysteresis, and the structural and morphological features of the pentacene layer grown on the gate dielectric was characterized and compared with the properties of pentacene grown on a polystyrene surface.

  20. Homogeneous/Inhomogeneous-Structured Dielectrics and their Energy-Storage Performances.

    Science.gov (United States)

    Yao, Zhonghua; Song, Zhe; Hao, Hua; Yu, Zhiyong; Cao, Minghe; Zhang, Shujun; Lanagan, Michael T; Liu, Hanxing

    2017-05-01

    The demand for dielectric capacitors with higher energy-storage capability is increasing for power electronic devices due to the rapid development of electronic industry. Existing dielectrics for high-energy-storage capacitors and potential new capacitor technologies are reviewed toward realizing these goals. Various dielectric materials with desirable permittivity and dielectric breakdown strength potentially meeting the device requirements are discussed. However, some significant limitations for current dielectrics can be ascribed to their low permittivity, low breakdown strength, and high hysteresis loss, which will decrease their energy density and efficiency. Thus, the implementation of dielectric materials for high-energy-density applications requires the comprehensive understanding of both the materials design and processing. The optimization of high-energy-storage dielectrics will have far-reaching impacts on the sustainable energy and will be an important research topic in the near future. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. The corkscrew instability of a Freedericksz domain wall in a nematic liquid crystal

    CERN Document Server

    Munoz, A D L; Müller, M; Schoepf, W; Rehberg, I

    2003-01-01

    A liquid crystal with slightly positive dielectric anisotropy is investigated in the planar configuration. This system allows for competition between electroconvection and the homogeneous Freedericksz transition, leading to a rather complicated bifurcation scenario. We report measurements of a novel instability leading to the 'corkscrew' pattern. This state is closely connected to the Freedericksz state as it manifests itself as a regular modulation along a Freedericksz domain wall, although its frequency dependence indicates that electroconvection must play a crucial role. It can be understood in terms of a pitchfork bifurcation from a straight domain wall. Quantitative characterization is performed in terms of amplitude, wavelength and relaxation time. Its wavelength is of the order of the probe thickness, while its ondulation amplitude is an order of magnitude smaller. The relaxation time is comparable to the one obtained for electroconvection.

  2. Summary report : working group 5 on 'electron beam-driven plasma and structure based acceleration concepts'

    International Nuclear Information System (INIS)

    Conde, M. E.; Katsouleas, T.

    2000-01-01

    The talks presented and the work performed on electron beam-driven accelerators in plasmas and structures are summarized. Highlights of the working group include new experimental results from the E-157 Plasma Wakefield Experiment, the E-150 Plasma Lens Experiment and the Argonne Dielectric Structure Wakefield experiments. The presentations inspired discussion and analysis of three working topics: electron hose instability, ion channel lasers and the plasma afterburner

  3. Electrical transport through single-wall carbon nanotube-anodic aluminum oxide-aluminum heterostructures

    International Nuclear Information System (INIS)

    Kukkola, Jarmo; Rautio, Aatto; Sala, Giovanni; Pino, Flavio; Toth, Geza; Leino, Anne-Riikka; Maeklin, Jani; Jantunen, Heli; Uusimaeki, Antti; Kordas, Krisztian; Gracia, Eduardo; Terrones, Mauricio; Shchukarev, Andrey; Mikkola, Jyri-Pekka

    2010-01-01

    Aluminum foils were anodized in sulfuric acid solution to form thick porous anodic aluminum oxide (AAO) films of thickness ∼6 μm. Electrodes of carboxyl-functionalized single-wall carbon nanotube (SWCNT) thin films were inkjet printed on the anodic oxide layer and the electrical characteristics of the as-obtained SWCNT-AAO-Al structures were studied. Nonlinear current-voltage transport and strong temperature dependence of conduction through the structure was measured. The microstructure and chemical composition of the anodic oxide layer was analyzed using transmission and scanning electron microscopy as well as x-ray photoelectron spectroscopy. Schottky emission at the SWCNT-AAO and AAO-Al interfaces allowed by impurity states in the anodic aluminum oxide film together with ionic surface conduction on the pore walls of AAO gives a reasonable explanation for the measured electrical conduction. Calcined AAO is proposed as a dielectric material for SWCNT-field effect transistors.

  4. Dielectric material options for integrated capacitors

    NARCIS (Netherlands)

    Ruhl, G.; Lehnert, W.; Lukosius, M.; Wenger, C.; Baristiran Kaynak, C.; Blomberg, T.; Haukka, S.; Baumann, P.K.; Besling, W.F.A.; Roest, A.L.; Riou, B.; Lhostis, S.; Halimaou, A.; Roozeboom, F.; Langereis, E.; Kessels, W.M.M.; Zauner, A.; Rushworth, S.A.

    2014-01-01

    Future MIM capacitor generations will require significantly increased specific capacitances by utilization of high-k dielectric materials. In order to achieve high capacitance per chip area, these dielectrics have to be deposited in three-dimensional capacitor structures by ALD or AVD (atomic vapor

  5. Nanostructure multilayer dielectric materials for capacitors and insulators

    Science.gov (United States)

    Barbee, Jr., Troy W.; Johnson, Gary W.

    1998-04-21

    A capacitor is formed of at least two metal conductors having a multilayer dielectric and opposite dielectric-conductor interface layers in between. The multilayer dielectric includes many alternating layers of amorphous zirconium oxide (ZrO.sub.2) and alumina (Al.sub.2 O.sub.3). The dielectric-conductor interface layers are engineered for increased voltage breakdown and extended service life. The local interfacial work function is increased to reduce charge injection and thus increase breakdown voltage. Proper material choices can prevent electrochemical reactions and diffusion between the conductor and dielectric. Physical vapor deposition is used to deposit the zirconium oxide (ZrO.sub.2) and alumina (Al.sub.2 O.sub.3) in alternating layers to form a nano-laminate.

  6. Infrared and THz spectroscopy of nanostructured dielectrics

    Directory of Open Access Journals (Sweden)

    Jan Petzelt

    2009-09-01

    Full Text Available Results achieved using the infrared/THz spectroscopy of various inhomogeneous dielectrics in the Department of Dielectrics, Institute of Physics, Prague, during the last decade are briefly reviewed. The discussion concerns high-permittivity ceramics with inevitable low-permittivity dead layers along the grain boundaries, relaxor ferroelectrics with highly anisotropic polar nano-regions, classical matrix-type composites, core-shell composites, filled nanoporous glasses, polycrystalline and epitaxial thin films, heterostructures and superlattices on dielectric substrates. The analysis using models based on the effective medium approach is discussed. The importance of depolarizing field and of the percolation of components on the effective ac dielectric response and the excitations contributing to it are emphasized.

  7. Dielectric Properties of PANI/CuO Nanocomposites

    Science.gov (United States)

    Ambalagi, Sharanabasamma M.; Devendrappa, Mahalesh; Nagaraja, Sannakki; Sannakki, Basavaraja

    2018-02-01

    The combustion method is used to prepare the Copper Oxide (CuO) nanoparticles. The nanocomposites of Polyaniline (PANI) by doping with copper oxide nanoparticles have synthesized at 10, 20, 30, 40 and 50 different weight percentages during the in-situ polymerization. The samples of nanocomposite of PANI-CuO were characterized by using X-Ray diffraction (XRD) technique. The physical properties such as dielectric constant, dielectric loss and A C conductivity of the nanocomposites are studied as a function of frequency in the range 5Hz-35MHz at room temperature. It is found that the dielectric constant decreases as the frequency increases. The dielectric constant it remains constant at higher frequencies and it is also observed that in particular frequency both the dielectric constant and dielectric loss are decreased as a weight percentage of CuO increased. In case of AC conductivity it is found that as the frequency increases the AC conductivity remains constant up to 3.56MHz and afterwards it increases as frequency increases. This is due to the increase in charge carriers through the hopping mechanism in the polymer nanocomposites. It is also observed that as a weight percentage of CuO increased the AC conductivity is also increasing at a particular frequency.

  8. Dielectric silicone elastomers with mixed ceramic nanoparticles

    International Nuclear Information System (INIS)

    Stiubianu, George; Bele, Adrian; Cazacu, Maria; Racles, Carmen; Vlad, Stelian; Ignat, Mircea

    2015-01-01

    Highlights: • Composite ceramics nanoparticles (MCN) with zirconium dioxide and lead zirconate. • Dielectric elastomer films wDith PDMS matrix and MCN as dielectric filler. • Hydrophobic character—water resistant and good flexibility specific to siloxanes. • Increased value of dielectric constant with the content of MCN in dielectric films. • Increased energy output from uniaxial deformation of the dielectric elastomer films. - Abstract: A ceramic material consisting in a zirconium dioxide-lead zirconate mixture has been obtained by precipitation method, its composition being proved by wide angle X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The average diameter of the ceramic particles ranged between 50 and 100 nm, as revealed by transmission electron microscopy images. These were surface treated and used as filler for a high molecular mass polydimethylsiloxane-α,ω-diol (Mn = 450,000) prepared in laboratory, the resulted composites being further processed as films and crosslinked. A condensation procedure, unusual for polydimethylsiloxane having such high molecular mass, with a trifunctional silane was approached for the crosslinking. The effect of filler content on electrical and mechanical properties of the resulted materials was studied and it was found that the dielectric permittivity of nanocomposites increased in line with the concentration of ceramic nanoparticles

  9. Dielectric silicone elastomers with mixed ceramic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Stiubianu, George, E-mail: george.stiubianu@icmpp.ro [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Bele, Adrian; Cazacu, Maria; Racles, Carmen; Vlad, Stelian [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Ignat, Mircea [National R& D Institute for Electrical Engineering ICPE-CA Bucharest, Splaiul Unirii 313, District 3, Bucharest 030138 (Romania)

    2015-11-15

    Highlights: • Composite ceramics nanoparticles (MCN) with zirconium dioxide and lead zirconate. • Dielectric elastomer films wDith PDMS matrix and MCN as dielectric filler. • Hydrophobic character—water resistant and good flexibility specific to siloxanes. • Increased value of dielectric constant with the content of MCN in dielectric films. • Increased energy output from uniaxial deformation of the dielectric elastomer films. - Abstract: A ceramic material consisting in a zirconium dioxide-lead zirconate mixture has been obtained by precipitation method, its composition being proved by wide angle X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The average diameter of the ceramic particles ranged between 50 and 100 nm, as revealed by transmission electron microscopy images. These were surface treated and used as filler for a high molecular mass polydimethylsiloxane-α,ω-diol (Mn = 450,000) prepared in laboratory, the resulted composites being further processed as films and crosslinked. A condensation procedure, unusual for polydimethylsiloxane having such high molecular mass, with a trifunctional silane was approached for the crosslinking. The effect of filler content on electrical and mechanical properties of the resulted materials was studied and it was found that the dielectric permittivity of nanocomposites increased in line with the concentration of ceramic nanoparticles.

  10. Dielectric loss against piezoelectric power harvesting

    Science.gov (United States)

    Liang, Junrui; Shu-Hung Chung, Henry; Liao, Wei-Hsin

    2014-09-01

    Piezoelectricity is one of the most popular electromechanical transduction mechanisms for constructing kinetic energy harvesting systems. When a standard energy harvesting (SEH) interface circuit, i.e., bridge rectifier plus filter capacitor, is utilized for collecting piezoelectric power, the previous literature showed that the power conversion can be well predicted without much consideration for the effect of dielectric loss. Yet, as the conversion power gets higher by adopting power-boosting interface circuits, such as synchronized switch harvesting on inductor (SSHI), the neglect of dielectric loss might give rise to deviation in harvested power estimation. Given the continuous progress on power-boosting interface circuits, the role of dielectric loss in practical piezoelectric energy harvesting (PEH) systems should receive attention with better evaluation. Based on the integrated equivalent impedance network model, this fast track communication provides a comprehensive study on the susceptibility of harvested power in PEH systems under different conditions. It shows that, dielectric loss always counteracts piezoelectric power harvesting by causing charge leakage across piezoelectric capacitance. In particular, taking corresponding ideal lossless cases as references, the counteractive effect might be aggravated under one of the five conditions: larger dielectric loss tangent, lower vibration frequency, further away from resonance, weaker electromechanical coupling, or using power-boosting interface circuit. These relationships are valuable for the study of PEH systems, as they not only help explain the role of dielectric loss in piezoelectric power harvesting, but also add complementary insights for material, structure, excitation, and circuit considerations towards holistic evaluation and design for practical PEH systems.

  11. Dielectric loss against piezoelectric power harvesting

    International Nuclear Information System (INIS)

    Liang, Junrui; Shu-Hung Chung, Henry; Liao, Wei-Hsin

    2014-01-01

    Piezoelectricity is one of the most popular electromechanical transduction mechanisms for constructing kinetic energy harvesting systems. When a standard energy harvesting (SEH) interface circuit, i.e., bridge rectifier plus filter capacitor, is utilized for collecting piezoelectric power, the previous literature showed that the power conversion can be well predicted without much consideration for the effect of dielectric loss. Yet, as the conversion power gets higher by adopting power-boosting interface circuits, such as synchronized switch harvesting on inductor (SSHI), the neglect of dielectric loss might give rise to deviation in harvested power estimation. Given the continuous progress on power-boosting interface circuits, the role of dielectric loss in practical piezoelectric energy harvesting (PEH) systems should receive attention with better evaluation. Based on the integrated equivalent impedance network model, this fast track communication provides a comprehensive study on the susceptibility of harvested power in PEH systems under different conditions. It shows that, dielectric loss always counteracts piezoelectric power harvesting by causing charge leakage across piezoelectric capacitance. In particular, taking corresponding ideal lossless cases as references, the counteractive effect might be aggravated under one of the five conditions: larger dielectric loss tangent, lower vibration frequency, further away from resonance, weaker electromechanical coupling, or using power-boosting interface circuit. These relationships are valuable for the study of PEH systems, as they not only help explain the role of dielectric loss in piezoelectric power harvesting, but also add complementary insights for material, structure, excitation, and circuit considerations towards holistic evaluation and design for practical PEH systems. (fast track communications)

  12. Elaboration and dielectric characterization of a doped ferroelectric ...

    African Journals Online (AJOL)

    ... 1150,1180 and 1200 °C successively to optimize the sintering temperature optimal where the density of the sample is maximum (near theoretical density) and therefore the product has better physical quality. The study of dielectric properties of all samples showed a high permittivity dielectric εr = 18018, low dielectric loss: ...

  13. Note: On the dielectric constant of nanoconfined water

    OpenAIRE

    Zhang, Chao

    2018-01-01

    Investigations of dielectric properties of water in nanoconfinement are highly relevant for various applications. Here, using a simple capacitor model, we show that the low dielectric constant of nanoconfined water found in molecular dynamics simulations can be largely explained by the so-called dielectric dead-layer effect known for ferroelectric nanocapacitors.

  14. Electrode/Dielectric Strip For High-Energy-Density Capacitor

    Science.gov (United States)

    Yen, Shiao-Ping S.

    1994-01-01

    Improved unitary electrode/dielectric strip serves as winding in high-energy-density capacitor in pulsed power supply. Offers combination of qualities essential for high energy density: high permittivity of dielectric layers, thinness, and high resistance to breakdown of dielectric at high electric fields. Capacitors with strip material not impregnated with liquid.

  15. Dielectric measurements on PWB materials at microwave frequencies

    Indian Academy of Sciences (India)

    Unknown

    the angular frequency and c0 the velocity of light, c the thickness of the ... Dielectric parameters, absorption index and refractive index for pure PSF and pure PMMA at 8⋅92 GHz frequency and at 35°C temperature. Dielectric. Dielectric. Loss. Relaxation. Conductivity Absorption. Refractive. Thickness, constant loss tangent.

  16. Unified formulation for linear accelerator design

    International Nuclear Information System (INIS)

    Farkas, Z.D.

    1986-01-01

    Expressions for peak and average powers required to produce a given average gradient in an accelerator section are given. They are valid for both lossy and lossless (superconducting) sections, for both traveling wave and standing wave sections, and for pulsed or continuous wave rf input. The expressions are given in terms of structure parameters that are equally applicable to traveling wave or standing waves. These parameters delineate the effect of wall losses and energy required to build up the field. For both traveling wave and standing wave sections it is possible to make the rf pulse length short enough to make the wall losses negligible at the expense of increased peak power requirement. Therefore, the expressions includes the effects of pulse compression

  17. Unified formulation for linear accelerator design

    International Nuclear Information System (INIS)

    Farkas, Z.D.

    1986-05-01

    Expressions for peak and average powers required to produce a given average gradient in an accelerator section are given. They are valid for both lossy and lossless (superconducting) sections, for both traveling wave and standing wave sections, and for pulsed or continuous wave rf input. The expressions are given in terms of structure parameters that are equally applicable to traveling wave or standing wave. These parameters delineate the effect of wall losses and energy required to build up the field. For both traveling wave and standing wave sections it is possible to make the rf pulse length short enough to make the wall losses negligible at the expense of increased peak power requirement. Therefore the expressions will include the effects of pulse compression. 6 refs., 7 figs

  18. Radiation pressure on a dielectric surface

    International Nuclear Information System (INIS)

    Hirose, A.

    2010-01-01

    The radiation pressure on an insulating dielectric medium should be calculable from the force acting on the polarization vector P. The well-known force proposed by Gordon (Phys. Rev. A, 8, 14 (1973) disappears in the case of a steady-state plane wave. A new form of force explicitly involving the polarization vector is proposed and applied to determine the partition of the incident momentum among the reflected and transmitted wave, and the dielectric medium. The momentum of electromagnetic wave in a dielectric medium thus found is consistent with the classical relationship, wave momentum flux density = wave intensity/wave velocity. (author)

  19. Generation and characterization of electron bunches with ramped current profiles in a dual-frequency superconducting linear accelerator.

    Science.gov (United States)

    Piot, P; Behrens, C; Gerth, C; Dohlus, M; Lemery, F; Mihalcea, D; Stoltz, P; Vogt, M

    2012-01-20

    We report on the successful experimental generation of electron bunches with ramped current profiles. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a superconducing radio frequency linear accelerator operating at two frequencies and a current-enhancing dispersive section. The produced ~700-MeV bunches have peak currents of the order of a kilo-Ampère. Data taken for various accelerator settings demonstrate the versatility of the method and, in particular, its ability to produce current profiles that have a quasilinear dependency on the longitudinal (temporal) coordinate. The measured bunch parameters are shown, via numerical simulations, to produce gigavolt-per-meter peak accelerating electric fields with transformer ratios larger than 2 in dielectric-lined waveguides. © 2012 American Physical Society

  20. High thermal conductivity lossy dielectric using co-densified multilayer configuration

    Science.gov (United States)

    Tiegs, Terry N.; Kiggans, Jr., James O.

    2003-06-17

    Systems and methods are described for loss dielectrics. A method of manufacturing a lossy dielectric includes providing at least one high dielectric loss layer and providing at least one high thermal conductivity-electrically insulating layer adjacent the at least one high dielectric loss layer and then densifying together. The systems and methods provide advantages because the lossy dielectrics are less costly and more environmentally friendly than the available alternatives.

  1. Improving uniformity of atmospheric-pressure dielectric barrier discharges using dual frequency excitation

    Science.gov (United States)

    Liu, Y.; Peeters, F. J. J.; Starostin, S. A.; van de Sanden, M. C. M.; de Vries, H. W.

    2018-01-01

    This letter reports a novel approach to improve the uniformity of atmospheric-pressure dielectric barrier discharges using a dual-frequency excitation consisting of a low frequency (LF) at 200 kHz and a radio frequency (RF) at 13.56 MHz. It is shown that due to the periodic oscillation of the RF electric field, the electron acceleration and thus the gas ionization is temporally modulated, i.e. enhanced and suppressed during each RF cycle. As a result, the discharge development is slowed down with a lower amplitude and a longer duration of the LF discharge current. Hence, the RF electric field facilitates improved stability and uniformity simultaneously allowing a higher input power.

  2. Experimental Characterization of Dielectric Properties in Fluid Saturated Artificial Shales

    Directory of Open Access Journals (Sweden)

    Roman Beloborodov

    2017-01-01

    Full Text Available High dielectric contrast between water and hydrocarbons provides a useful method for distinguishing between producible layers of reservoir rocks and surrounding media. Dielectric response at high frequencies is related to the moisture content of rocks. Correlations between the dielectric permittivity and specific surface area can be used for the estimation of elastic and geomechanical properties of rocks. Knowledge of dielectric loss-factor and relaxation frequency in shales is critical for the design of techniques for effective hydrocarbon extraction and production from unconventional reservoirs. Although applicability of dielectric measurements is intriguing, the data interpretation is very challenging due to many factors influencing the dielectric response. For instance, dielectric permittivity is determined by mineralogical composition of solid fraction, volumetric content and composition of saturating fluid, rock microstructure and geometrical features of its solid components and pore space, temperature, and pressure. In this experimental study, we investigate the frequency dependent dielectric properties of artificial shale rocks prepared from silt-clay mixtures via mechanical compaction. Samples are prepared with various clay contents and pore fluids of different salinity and cation compositions. Measurements of dielectric properties are conducted in two orientations to investigate the dielectric anisotropy as the samples acquire strongly oriented microstructures during the compaction process.

  3. [Determination of electric field distribution in dielectric barrier surface glow discharge by spectroscopic method].

    Science.gov (United States)

    Li, Xue-chen; Jia, Peng-ying; Liu, Zhi-hui; Li, Li-chun; Dong, Li-fang

    2008-12-01

    In the present paper, stable glow discharges were obtained in air at low pressure with a dielectric barrier surface discharge device. Light emission from the discharge was detected by photomultiplier tubes and the research results show that the light signal exhibited one discharge pulse per half cycle of the applied voltage. The light pulses were asymmetric between the positive half cycle and the negative one of the applied voltage. The images of the glow surface discharge were processed by Photoshop software and the results indicate that the emission intensity remained almost constant for different places with the same distance from the powered electrode, while the emission intensity decreased with the distance from the powered electrode increasing. In dielectric barrier discharge, net electric field is determined by the applied voltage and the wall charges accumulated on the dielectric layer during the discharge, and consequently, it is important to obtain information about the net electric field distribution. For this purpose, optical emission spectroscopy method was used. The distribution of the net electric field can be deduced from the intensity ratio of spectral line 391.4 nm emitted from the first negative system of N2+ (B 2sigma u+ -->X 2sigma g+) to 337.1 nm emitted from the second positive system of N2 (C 3IIu-B 3IIg). The research results show that the electric field near the powered electric field is higher than at the edge of the discharge. These experimental results are very important for numerical study and industrial application of the surface discharge.

  4. Thermodynamics and instability of dielectric elastomer (Conference Presentation)

    Science.gov (United States)

    Liu, Liwu; Liu, Yanju; Leng, Jinsong; Mu, Tong

    2017-04-01

    Dielectric elastomer is a kind of typical soft active material. It can deform obviously when subjected to an external voltage. When a dielectric elastomer with randomly oriented dipoles is subject to an electric field, the dipoles will rotate to and align with the electric field. The polarization of the dielectric elastomer may be saturated when the voltage is high enough. When subjected to a mechanical force, the end-to-end distance of each polymer chain, which has a finite contour length, will approach the finite value, reaching a limiting stretch. On approaching the limiting stretch, the elastomer stiffens steeply. Here, we develop a thermodynamic constitutive model of dielectric elastomers undergoing polarization saturation and strain-stiffening, and then investigate the stability (electromechanical stability, snap-through stability) and voltage induced deformation of dielectric elastomers. Analytical solution has been obtained and it reveals the marked influence of the extension limit and polarization saturation limit on its instability. The developed thermodynamic constitutive model and simulation results would be helpful in future to the research of dielectric elastomer based high-performance transducers.

  5. Laser amplification in excited dielectrics

    Science.gov (United States)

    Winkler, Thomas; Haahr-Lillevang, Lasse; Sarpe, Cristian; Zielinski, Bastian; Götte, Nadine; Senftleben, Arne; Balling, Peter; Baumert, Thomas

    2018-01-01

    Wide-bandgap dielectrics such as glasses or water are transparent at visible and infrared wavelengths. This changes when they are exposed to ultrashort and highly intense laser pulses. Different interaction mechanisms lead to the appearance of various transient nonlinear optical phenomena. Using these, the optical properties of dielectrics can be controlled from the transparent to the metal-like state. Here we expand this range by a yet unexplored mechanism in excited dielectrics: amplification. In a two-colour pump-probe experiment, we show that a 400 nm femtosecond laser pulse is coherently amplified inside an excited sapphire sample on a scale of a few micrometres. Simulations strongly support the proposed two-photon stimulated emission process, which is temporally and spatially controllable. Consequently, we expect applications in all fields that demand strongly localized amplification.

  6. Collective ion acceleration via laser controlled ionization channel

    International Nuclear Information System (INIS)

    Destler, W.W.; O'Shea, P.G.; Rodgers, J.; Segalov, Z.

    1987-01-01

    Initial results from a successful laser-controlled collective ion acceleration experiment at the University of Maryland are presented. In the experiment, positive ions are trapped in the potential well at the head of an intense relativistic electron beam injected at current levels above the space charge limit. Seed ions for acceleration are provided by puff valve injection of a neutral gas cloud localized to within 3 cm of the injection point. Control over the acceleration of the well and the ions is then achieved by means of a laser-generated ionization channel produced by passing the light from a Q-switched ruby laser through a series of partially and fully reflecting mirrors in such a way as to provide time-sequenced laser ionization of a target located on the drift tube wall. Using this system, controlled acceleration of protons at a rate of approximately 40 MV/m has been demonstrated over a distance of about 50 cm

  7. 3-D simulation of hanging wall effect at dam site

    Science.gov (United States)

    Zhang, L.; Xu, Y.

    2017-12-01

    Hanging wall effect is one of the near fault effects. This paper focuses on the difference of the ground motions on the hanging wall side between the footwall side of the fault at dam site considering the key factors, such as actual topography, the rupture process. For this purpose, 3-D ground motions are numerically simulated by the spectrum element method (SEM), which takes into account the physical mechanism of generation and propagation of seismic waves. With the SEM model of 548 million DOFs, excitation and propagation of seismic waves are simulated to compare the difference between the ground motion on the hanging wall side and that on the footwall side. Take Dagangshan region located in China as an example, several seismogenic finite faults with different dip angle are simulated to investigate the hanging wall effect. Furthermore, by comparing the ground motions of the receiving points, the influence of several factors on hanging wall effect is investigated, such as the dip of the fault and the fault type (strike slip fault or dip-slip fault). The peak acceleration on the hanging wall side is obviously larger than those on the footwall side, which numerically evidences the hanging wall effect. Besides, the simulation shows that only when the dip is less than 70° does the hanging wall effect deserve attention.

  8. Radiography of large-volume thick-walled structures using transportable high-energy sources

    International Nuclear Information System (INIS)

    Vanek, J.; Gross, E.

    1994-01-01

    Carried by a Renault Saviem truck, the ORION 4 MeV linear accelerator manufactured by the French company CGR MeV proved to be well suited for quality control of welded joints of heavy thick-walled facilities performed directly in the manufacturing plant halls or at the construction sites, as well as for radiographic testing of steel and concrete structures. The operating principles and parameters of the accelerator are given. Steel up to 200 mm thick and concrete up to 550 mm thick can be inspected. Dosimetric data show that the use of the accelerator is radiologically safe. (Z.S.). 2 figs., 5 refs

  9. Decay of plasma cluster accelerated by coaxial gun

    International Nuclear Information System (INIS)

    Kubes, P.; Hruska, J.; Bacilek, J.

    1978-01-01

    The decay of an air cluster accelerated in a vacuum tube is studied. The time dependence of electron density and electron temperature is introduced and the effect of different recombination processes is discussed. The observed plasma decay shows an exponential law, is independent of the gun regime and may be explained by ambipolar diffusion to the tube walls. (author)

  10. Investigation of charge dissipation in jet fuel in a dielectric fuel tank

    Science.gov (United States)

    Kitanin, E. L.; Kravtsov, P. A.; Trofimov, V. A.; Kitanina, E. E.; Bondarenko, D. A.

    2017-09-01

    The electrostatic charge dissipation process in jet fuel in a polypropylene tank was investigated experimentally. Groundable metallic terminals were installed in the tank walls to accelerate the dissipation process. Several sensors and an electrometer with a current measuring range from 10-11 to 10-3 A were specifically designed to study the dissipation rates. It was demonstrated that thanks to the sensors and the electrometer one can obtain reliable measurements of the dissipation rate and look at how it is influenced by the number and locations of the terminals. Conductivity of jet fuel and effective conductivity of the tank walls were investigated in addition. The experimental data agree well with the numerical simulation results obtained using COMSOL software package.

  11. Dielectric Optical Antenna Emitters and Metamaterials

    Science.gov (United States)

    Schuller, Jon

    2009-03-01

    Optical antennas are critical components in nanophotonics research due to their unparalleled ability to concentrate electromagnetic energy into nanoscale volumes. Researchers typically construct such antennas from wavelength-size metallic structures. However, recent research has begun to exploit the scattering resonances of high-permittivity particles to realize all-dielectric optical antennas, emitters, and metamaterials. In this talk, we experimentally and theoretically characterize the resonant modes of subwavelength rod-shaped dielectric particles and demonstrate their use in negative index metamaterials and novel infrared light emitters. At mid-infrared frequencies, Silicon Carbide (SiC) is an ideal system for studying the behavior of dielectric optical antennas. At frequencies below the TO phonon resonance, SiC behaves like a dielectric with very large refractive index. Using infrared spectroscopy and analytical Mie calculations we show that individual rod-shaped SiC particles exhibit a multitude of resonant modes. Detailed investigations of these SiC optical antennas reveal a wealth of new physics and applications. We discuss the distinct electromagnetic field profile for each mode, and demonstrate that two of the dielectric-type Mie resonances can be combined in a particle array to form a negative index metamaterial [1]. We further show that these particles can serve as ``broadcasting'' antennas. Using a custom-built thermal emission microscope we collect emissivity spectra from single SiC particles at elevated temperatures, highlighting their use as subwavelength resonant light emitters. Finally, we derive and verify a variety of general analytical results applicable to all cylindrical dielectric antennas and discuss extensions of the demonstrated concepts to different materials systems and frequency regimes. [1] J.A. Schuller, et al., Phys. Rev. Lett. 99, 107401 (2007)

  12. Microemulsions as model fluids for enhanced oil recovery: dynamics adjacent to planar hydrophilic walls

    Directory of Open Access Journals (Sweden)

    Mattauch S.

    2012-10-01

    Full Text Available After the dynamics of microemulsions adjacent to a planar hydrophilic wall have been characterized using grazing incidence neutron spin echo spectroscopy, the model of Seifert was employed to explain the discovered acceleration for the surface near lamellar ordered membranes. Reflections of hydrodynamic waves by the wall – or the volume conservation between the membrane and the wall – explain faster relaxations and, therefore, a lubrication effect that is important for flow fields in narrow pores. The whole scenery is now spectated by using different scenarios of a bicontinuous microemulsion exposed to clay particles and of a lamellar microemulsion adjacent to a planar wall. The Seifert concept could successfully be transferred to the new problems.

  13. Time-dependent electrophoresis of a dielectric spherical particle embedded in Brinkman medium

    Science.gov (United States)

    Saad, E. I.; Faltas, M. S.

    2018-04-01

    An expression for electrophoretic apparent velocity slip in the time-dependent flow of an electrolyte solution saturated in a charged porous medium within an electric double layer adjacent to a dielectric plate under the influence of a tangential uniform electric field is derived. The velocity slip is used as a boundary condition to solve the electrophoretic motion of an impermeable dielectric spherical particle embedded in an electrolyte solution saturated in porous medium under the unsteady Darcy-Brinkman model. Throughout the system, a uniform electric field is applied and maintains with constant strength. Two cases are considered, when the electric double layer enclosing the particle is thin, but finite and when of a particle with a thick double layer. Expressions for the electrophoretic mobility of the particle as functions of the relevant parameters are found. Our results indicate that the time scale for the growth of mobility is significant and small for high permeability. Generally, the effect of the relaxation time for starting electrophoresis is negligible, irrespective of the thickness of the double layer and permeability of the medium. The effects of the elapsed time, permeability, mass density and Debye length parameters on the fluid velocity, the electrophoretic mobility and the acceleration are shown graphically.

  14. Aging of Dielectric Properties below Tg

    DEFF Research Database (Denmark)

    Olsen, Niels Boye; Dyre, Jeppe; Christensen, Tage Emil

    The dielectric loss at 1Hz in TPP is studied during a temperature step from one equilibrium state to another. In the applied cryostate the temperature can be equilibrated on a timescale of 1 second. The aging time dependence of the dielectric loss is studied below Tg applying temperature steps...

  15. Effect of Nb doping on sintering and dielectric properties of PZT ceramics

    Directory of Open Access Journals (Sweden)

    Ali Mirzaei

    2016-09-01

    Full Text Available The extensive use of piezoelectric ceramics such as lead zirconate titanate (PZT in different applications became possible with the development of donor or acceptor dopants. Therefore, studies on the effect of dopants on the properties of PZT ceramics are highly demanded. In this study undoped and 2.4 mol% Nb-doped PZT (PZTN powders were successfully obtained by a solid-state reaction and calcination at 850 °C for 2 h. Crystallinity and phase formation of the prepared powders were studied using X-ray diffraction (XRD. In order to study morphology of powders, scanning electron microscopy (SEM was performed. The crystalline PZT and Nb-doped PZT powders were pelleted into discs and sintered at 1100, 1150 and 1200 °C, with a heating rate of 10 °C/min, and holding time of 1–6 h to find the optimum combination of temperature and time to produce high density ceramics. Microstructural characterization was conducted on the fractured ceramic surfaces using SEM. Density measurements showed that maximal density of 95% of the theoretical density was achieved after sintering of PZT and PZTN ceramics at 1200 °C for 2 h and 4 h, respectively. However, the results of dielectric measurements showed that PZTN ceramics have higher relative permittivity (εr ∼17960 with lower Curie temperature (∼358 °C relative to PZT (εr = 16000 at ∼363 °C as a result of fine PZTN structure as well as presence of vacancies. In addition, dielectric loss (at 1 kHz of PZT and PZTN ceramics with 95% theoretical density was 0.0087 and 0.02, respectively. The higher dielectric loss in PZTN was due to easier domain wall motions in PZTN ceramics.

  16. The Electrical Breakdown of Thin Dielectric Elastomers

    DEFF Research Database (Denmark)

    Zakaria, Shamsul Bin; Morshuis, Peter H. F.; Yahia, Benslimane Mohamed

    2014-01-01

    Dielectric elastomers are being developed for use in actuators, sensors and generators to be used in various applications, such as artificial eye lids, pressure sensors and human motion energy generators. In order to obtain maximum efficiency, the devices are operated at high electrical fields....... This increases the likelihood for electrical breakdown significantly. Hence, for many applications the performance of the dielectric elastomers is limited by this risk of failure, which is triggered by several factors. Amongst others thermal effects may strongly influence the electrical breakdown strength....... In this study, we model the electrothermal breakdown in thin PDMS based dielectric elastomers in order to evaluate the thermal mechanisms behind the electrical failures. The objective is to predict the operation range of PDMS based dielectric elastomers with respect to the temperature at given electric field...

  17. Identification of structural relaxation in the dielectric response of water

    DEFF Research Database (Denmark)

    Hansen, Jesper Schmidt; Kisliuk, Alexander; Solokov, Alexei P.

    2016-01-01

    One century ago pioneering dielectric results obtained for water and n-alcohols triggered the advent of molecular rotation diffusion theory considered by Debye to describe the primary dielectric absorption in these liquids. Comparing dielectric, viscoelastic, and light scattering results, we...... unambiguously demonstrate that the structural relaxation appears only as a high-frequency shoulder in the dielectric spectra of water. In contrast, the main dielectric peak is related to a supramolecular structure, analogous to the Debye-like peak observed in monoalcohols....

  18. Plane-wave diffraction by periodic structures with artificial anisotropic dielectrics

    International Nuclear Information System (INIS)

    Kazerooni, Azadeh Semsar; Shahabadi, Mahmoud

    2010-01-01

    Periodic structures with artificial anisotropic dielectrics are studied. The artificial anisotropic dielectric material in this work is made of two alternating isotropic dielectric layers. By a proper choice of the dielectric constant of the layers, we can realize a uniaxial anisotropic medium with controllable anisotropy. The artificial anisotropic dielectric is then used in periodic structures. For these structures, the optical axis of the artificial dielectric is assumed to be parallel or perpendicular to the period of the structure. Diffraction of plane waves by these structures is analyzed by a fully vectorial rigorous matrix method based on a generalized transmission line (TL) formulation. The propagation constants and field distributions are computed and diffraction properties of such structures are studied to show that, by a proper choice of structural parameters, these periodic structures with artificial anisotropic dielectrics can be used as polarizers or polarizing mirrors

  19. Radiography of welded joints of thick-walled equipment using a mobile linear accelerator

    International Nuclear Information System (INIS)

    Vanek, J.; Krejci, M.

    1988-01-01

    The different aspects are discussed of the choice of a suitable source for nondestructive testing of materials of great thickness. The ORION mobile linear accelerator by the French company CGR MeV with 4 MeV electron energy was selected for the nondestructive testing of 200 mm thick welded joints. The principles and methods of health protection at work with this device are described as is the optimization of the economic efficiency of its use. Great attention was focused on the quality of the resulting image and the choice of intensifying foils. The one year operating experience with the accelerator is evaluated. (M.D.). 4 figs., 1 tab., 8 refs

  20. Dielectric lattice gauge theory

    International Nuclear Information System (INIS)

    Mack, G.

    1983-06-01

    Dielectric lattice gauge theory models are introduced. They involve variables PHI(b)epsilong that are attached to the links b = (x+esub(μ),x) of the lattice and take their values in the linear space g which consists of real linear combinations of matrices in the gauge group G. The polar decomposition PHI(b)=U(b)osub(μ)(x) specifies an ordinary lattice gauge field U(b) and a kind of dielectric field epsilonsub(ij)proportionalosub(i)osub(j)sup(*)deltasub(ij). A gauge invariant positive semidefinite kinetic term for the PHI-field is found, and it is shown how to incorporate Wilson fermions in a way which preserves Osterwalder Schrader positivity. Theories with G = SU(2) and without matter fields are studied in some detail. It is proved that confinement holds, in the sense that Wilson loop expectation values show an area law decay, if the Euclidean action has certain qualitative features which imply that PHI = 0 (i.e. dielectric field identical 0) is the unique maximum of the action. (orig.)

  1. Dielectric lattice gauge theory

    International Nuclear Information System (INIS)

    Mack, G.

    1984-01-01

    Dielectric lattice gauge theory models are introduced. They involve variables PHI(b)element ofG that are attached to the links b = (x+esub(μ), x) of the lattice and take their values in the linear space G which consists of real linear combinations of matrices in the gauge group G. The polar decomposition PHI(b)=U(b)sigmasub(μ)(x) specifies an ordinary lattice gauge field U(b) and a kind of dielectric field epsilonsub(ij)proportional sigmasub(i)sigmasub(j)sup(*)deltasub(ij). A gauge invariant positive semidefinite kinetic term for the PHI-field is found, and it is shown how to incorporate Wilson fermions in a way which preserves Osterwalder-Schrader positivity. Theories with G = SU(2) and without matter fields are studied in some detail. It is proved that confinement holds, in the sense that Wilson-loop expectation values show an area law decay, if the euclidean action has certain qualitative features which imply that PHI=0 (i.e. dielectric field identical 0) is the unique maximum of the action. (orig.)

  2. Beam, vacuum and walls, a 3-body interaction

    International Nuclear Information System (INIS)

    Arianer, J.

    2002-11-01

    The interactions between beams of accelerated particles, residual gas and walls involve complex physical processes. In most cases these interactions affect the quality of the vacuum and the value of the pressure. This course reviews all these interactions in a pedagogical and practical way that may be useful for any user of devices involving beams of particles. This document is made up of 6 chapters: 1) basic notions (Maxwell-Boltzmann distribution, kinematics of charged particles, collisions, excitation and ionization), 2) properties of beams (emittance, local effects, and synchrotron radiation), 3) interactions between residual gas and particle beams (Bremsstrahlung radiation, energy loss due to ionization, charge shift of ion beams, photo-absorption and photo-ionization, and slowing-down in a plasma), 4) surface properties (crystal structure, and interaction between surface and the residual gas), 5) interaction between the beam and walls (reflection and diffraction of electrons, secondary emission of electrons, desorption induced by electron and ion impacts, photon production, ion-wall interaction, sputtering, ion penetration, surface ionization and thermal-ionization), and 6) radiation-wall interaction (diffusion, damping, photo-electric effect, desorption induced by photons, pair production and laser-surface interaction). (A.C.)

  3. A consideration on pipe-wall thinning mechanisms from an aspect of fluid-mechanics

    International Nuclear Information System (INIS)

    Inada, Fumio; Yoneda, Kimitoshi; Morita, Ryo; Fujiwara, Kazutoshi; Furuya, Masahiro

    2008-01-01

    The contribution of the fluid mechanics to the piping wall thinning phenomena was investigated. It was shown that the fluid force to the wall was quite different between flow accelerated corrosion (FAC) and erosion. The turbulent mass transfer, which is one of the primary factors of FAC, was analogous to the turbulent heat transfer. The model that the molecular transport in the viscous sublayer nearby soon of wall was predominant was practicable. In addition, the mass transport was predicted using commercial codes of computational fluid dynamics. Some prediction results of the mass transfer in orifice and the elbow using above techniques were explained. (author)

  4. Evaluation of Dielectric-Barrier-Discharge Actuator Substrate Materials

    Science.gov (United States)

    Wilkinson, Stephen P.; Siochi, Emilie J.; Sauti, Godfrey; Xu, Tian-Bing; Meador, Mary Ann; Guo, Haiquan

    2014-01-01

    A key, enabling element of a dielectric barrier discharge (DBD) actuator is the dielectric substrate material. While various investigators have studied the performance of different homogeneous materials, most often in the context of related DBD experiments, fundamental studies focused solely on the dielectric materials have received less attention. The purpose of this study was to conduct an experimental assessment of the body-force-generating performance of a wide range of dielectric materials in search of opportunities to improve DBD actuator performance. Materials studied included commonly available plastics and glasses as well as a custom-fabricated polyimide aerogel. Diagnostics included static induced thrust, electrical circuit parameters for 2D surface discharges and 1D volume discharges, and dielectric material properties. Lumped-parameter circuit simulations for the 1D case were conducted showing good correspondence to experimental data provided that stray capacitances are included. The effect of atmospheric humidity on DBD performance was studied showing a large influence on thrust. The main conclusion is that for homogeneous, dielectric materials at forcing voltages less than that required for streamer formation, the material chemical composition appears to have no effect on body force generation when actuator impedance is properly accounted for.

  5. A dielectric approach to high temperature superconductivity

    International Nuclear Information System (INIS)

    Mahanty, J.; Das, M.P.

    1989-01-01

    The dielectric response of an electron-ion system to the presence of a pair of charges is investigated. From the nature of the dielectric function, it is shown that a strong attractive pair formation is possible depending on the dispersion of the ion branches. The latter brings a reduction to the sound velocity which is used as a criterion for the superconductivity. By solving the BCS equation with the above dielectric function, we obtain a reasonable value of T/sub c/. 17 refs., 1 fig

  6. An experimental program for collective acceleration of ions using intense relativistic electron beams

    International Nuclear Information System (INIS)

    Vijayan, T.; Raychowdhury, P.; Iyengar, S.K.

    1992-01-01

    A program of collective ion acceleration using intense relativistic electron beam (IREB) of 0.25-1MeV, 6-80kA, 60ns on the Kilo Ampere Linear Injector (KALI) systems to accelerate light and heavy ions to high energies approaching GeV with currents over tens of amperes, is envisaged in this report. The accelerator will make use of the intense space-charge field of electron beam in vacuum for accelerating ions which are injected into it. For ion injection, various alternatives, such as, localized gas puff, dielectric insert, laser plasma, etc. have been considered as present and long-term objectives. Among the variety of diagnostic methods chosen for characterizing the accelerated ions include range-energy in foil, CR-39 track detector, nuclear activation technique and time-of-flight for energy and species determination; ion Faraday cup for current measurement; and Thomson parabola analyzer for determining the post-acceleration charge-state. In the proposed MAHAKALI collective accelerator, protons of energy over 10 MeV and higher charge state metal ions around a GeV are predicted using a REB of 1MeV, 30kA, 60ns from KALI-5000. In present experiments using KALI-200 with REB parameters of 250keV, 60kA, 80ns, protons over a MeV and carbon and fluorine ions respectively for 12MeV and 16MeV in significant currents have been accelerated. (author). 35 refs., figs., tabs

  7. Tuning of colossal dielectric constant in gold-polypyrrole composite nanotubes using in-situ x-ray diffraction techniques

    Energy Technology Data Exchange (ETDEWEB)

    Sarma, Abhisakh; Sanyal, Milan K., E-mail: milank.sanyal@saha.ac.in [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)

    2014-09-15

    In-situ x-ray diffraction technique has been used to study the growth process of gold incorporated polypyrrole nanotubes that exhibit colossal dielectric constant due to existence of quasi-one-dimensional charge density wave state. These composite nanotubes were formed within nanopores of a polycarbonate membrane by flowing pyrrole monomer from one side and mixture of ferric chloride and chloroauric acid from other side in a sample cell that allows collection of x-ray data during the reaction. The size of the gold nanoparticle embedded in the walls of the nanotubes was found to be dependent on chloroauric acid concentration for nanowires having diameter more than 100 nm. For lower diameter nanotubes the nanoparticle size become independent of chloroauric acid concentration and depends on the diameter of nanotubes only. The result of this study also shows that for 50 nm gold-polypyrrole composite nanotubes obtained with 5.3 mM chloroauric acid gives colossal dielectric constant of about 10{sup 7}. This value remain almost constant over a frequency range from 1Hz to 10{sup 6} Hz even at 80 K temperature.

  8. Tuning of colossal dielectric constant in gold-polypyrrole composite nanotubes using in-situ x-ray diffraction techniques

    Directory of Open Access Journals (Sweden)

    Abhisakh Sarma

    2014-09-01

    Full Text Available In-situ x-ray diffraction technique has been used to study the growth process of gold incorporated polypyrrole nanotubes that exhibit colossal dielectric constant due to existence of quasi-one-dimensional charge density wave state. These composite nanotubes were formed within nanopores of a polycarbonate membrane by flowing pyrrole monomer from one side and mixture of ferric chloride and chloroauric acid from other side in a sample cell that allows collection of x-ray data during the reaction. The size of the gold nanoparticle embedded in the walls of the nanotubes was found to be dependent on chloroauric acid concentration for nanowires having diameter more than 100 nm. For lower diameter nanotubes the nanoparticle size become independent of chloroauric acid concentration and depends on the diameter of nanotubes only. The result of this study also shows that for 50 nm gold-polypyrrole composite nanotubes obtained with 5.3 mM chloroauric acid gives colossal dielectric constant of about 107. This value remain almost constant over a frequency range from 1Hz to 106 Hz even at 80 K temperature.

  9. Stretched exponential relaxation and ac universality in disordered dielectrics

    DEFF Research Database (Denmark)

    Milovanov, Alexander V.; Rypdal, Kristoffer; Juul Rasmussen, Jens

    2007-01-01

    This paper is concerned with the connection between the properties of dielectric relaxation and alternating-current (ac) conduction in disordered dielectrics. The discussion is divided between the classical linear-response theory and a self-consistent dynamical modeling. The key issues are stretc......This paper is concerned with the connection between the properties of dielectric relaxation and alternating-current (ac) conduction in disordered dielectrics. The discussion is divided between the classical linear-response theory and a self-consistent dynamical modeling. The key issues...

  10. Interplay of domain walls and magnetization rotation on dynamic magnetization process in iron/polymer–matrix soft magnetic composites

    Energy Technology Data Exchange (ETDEWEB)

    Dobák, Samuel, E-mail: samuel.dobak@student.upjs.sk [Institute of Physics, Faculty of Science, Pavol Jozef Šafárik University, Park Angelinum 9, 041 54 Košice (Slovakia); Füzer, Ján; Kollár, Peter [Institute of Physics, Faculty of Science, Pavol Jozef Šafárik University, Park Angelinum 9, 041 54 Košice (Slovakia); Fáberová, Mária; Bureš, Radovan [Institute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 043 53 Košice (Slovakia)

    2017-03-15

    This study sheds light on the dynamic magnetization process in iron/resin soft magnetic composites from the viewpoint of quantitative decomposition of their complex permeability spectra into the viscous domain wall motion and magnetization rotation. We present a comprehensive view on this phenomenon over the broad family of samples with different average particles dimension and dielectric matrix content. The results reveal the pure relaxation nature of magnetization processes without observation of spin resonance. The smaller particles and higher amount of insulating resin result in the prevalence of rotations over domain wall movement. The findings are elucidated in terms of demagnetizing effects rising from the heterogeneity of composite materials. - Highlights: • A first decomposition of complex permeability into domain wall and rotation parts in soft magnetic composites. • A pure relaxation nature of dynamic magnetization processes. • A complete loss separation in soft magnetic composites. • The domain walls activity is considerably suppressed in composites with smaller iron particles and higher matrix content. • The demagnetizing field acts as a significant factor at the dynamic magnetization process.

  11. Quantum optics of dispersive dielectric media

    International Nuclear Information System (INIS)

    Lenac, Z.

    2003-01-01

    We quantize the electromagnetic field in a polar medium starting with the fundamental equations of motion. In our model the medium is described by a Lorenz-type dielectric function ε(r,ω) appropriate, e.g., for ionic crystals, metals, and inert dielectrics. There are no restrictions on the spatial behavior of the dielectric function, i.e., there can be many different polar media with arbitrary shapes. We assume no losses in our system so the dielectric function for the whole space is assumed as real. The quantization procedure is based on an expansion of the total field (transverse and longitudinal) in terms of the coupled (polariton) eigenmodes, and this approach incorporates all previous results derived for similar but restricted systems (e.g., without spatial or frequency dependence of coupled modes). Within the same model, we also quantize the Hamiltonian of a nonretarded electromagnetic field in polar media. Particular attention is paid to the derivation of the orthogonality and closure relations, which are used in a discussion of the fundamental (equal-time) commutation relations between the conjugate field operators

  12. Dielectric optical antenna thermal emitters and metamaterials

    Science.gov (United States)

    Schuller, Jonathan Aaron

    Optical antennas are critical components in nanophotonics research due to their unparalleled ability to concentrate electromagnetic energy into nanoscale volumes. Researchers typically construct such antennas from wavelength-size metallic structures. However, recent research has begun to exploit the scattering resonances of high-permittivity particles to realize all-dielectric optical antennas, emitters, and metamaterials. In this thesis, we experimentally and theoretically characterize the resonant modes of subwavelength rod-shaped dielectric particles and demonstrate their use in negative index metamaterials and novel infrared light emitters. At mid-infrared frequencies, Silicon Carbide (SiC) is an ideal system for studying the behavior of dielectric optical antennas. At frequencies below the TO phonon resonance, SiC behaves like a dielectric with very large refractive index. Using infrared spectroscopy and analytical Mie calculations we show that individual rod-shaped SiC particles exhibit a multitude of resonant modes. Detailed investigations of these SiC optical antennas reveal a wealth of new physics and applications. We discuss the distinct electromagnetic field profile for each mode, and demonstrate that two of the dielectric-type Mie resonances can be combined in a particle array to form a negative index metamaterial. We further show that these particles can serve as "broadcasting" antennas. Using a custom-built thermal emission microscope we collect emissivity spectra from single SiC particles at elevated temperatures, highlighting their use as subwavelength resonant light emitters. Finally, we derive and verify a variety of general analytical results applicable to all cylindrical dielectric antennas.

  13. Spatio-temporal dynamics of the white-eye square superlattice pattern in dielectric barrier discharge

    International Nuclear Information System (INIS)

    Wei, Lingyan; Dong, Lifang; Feng, Jianyu; Liu, Weibo; Fan, Weili; Pan, Yuyang

    2016-01-01

    We report on the first investigation of the white-eye square superlattice pattern (WESSP) in a dielectric barrier discharge system. The evolution of patterns with increasing voltage is given. A phase diagram of WESSP as functions of gas pressure p and argon concentration φ is presented. The spatio-temporal dynamics of the WESSP is studied by using an intensified charge-coupled device camera and photomultipliers. Results show that the WESSP consists of four different transient sublattices, whose discharge sequence is small spots—spots on the line—halos—central spots in each half voltage cycle. The discharge moment and position of each sublattice are dependent upon the field of the wall charges produced by all sublattices discharged previously. (paper)

  14. On dielectric breakdown statistics

    International Nuclear Information System (INIS)

    Tuncer, Enis; James, D Randy; Sauers, Isidor; Ellis, Alvin R; Pace, Marshall O

    2006-01-01

    In this paper, we investigate the dielectric breakdown data of some insulating materials and focus on the applicability of the two- and three-parameter Weibull distributions. A new distribution function is also proposed. In order to assess the model distribution's trustworthiness, we employ the Monte Carlo technique and, randomly selecting data-subsets from the whole dielectric breakdown data, determine whether the selected probability functions accurately describe the breakdown data. The utility and strength of the proposed expression are illustrated distinctly by the numerical procedure. The proposed expression is shown to be a valuable alternative to the Weibull ones

  15. Numerical study of the influence of dielectric tube on propagation of atmospheric pressure plasma jet based on coplanar dielectric barrier discharge

    Science.gov (United States)

    Haixin, HU; Feng, HE; Ping, ZHU; Jiting, OUYANG

    2018-05-01

    A 2D fluid model was employed to simulate the influence of dielectric on the propagation of atmospheric pressure helium plasma jet based on coplanar dielectric barrier discharge (DBD). The spatio-temporal distributions of electron density, ionization rate, electrical field, spatial charge and the spatial structure were obtained for different dielectric tubes that limit the helium flow. The results show that the change of the relative permittivity of the dielectric tube where the plasma jet travels inside has no influence on the formation of DBD itself, but has great impact on the jet propagation. The velocity of the plasma jet changes drastically when the jet passes from a tube of higher permittivity to one of lower permittivity, resulting in an increase in jet length, ionization rate and electric field, as well as a change in the distribution of space charges and discharge states. The radius of the dielectric tube has a great influence on the ring-shaped or solid bullet structure. These results can well explain the behavior of the plasma jet from the dielectric tube into the ambient air and the hollow bullet in experiments.

  16. Self-Healing, High-Permittivity Silicone Dielectric Elastomer

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Skov, Anne Ladegaard

    2016-01-01

    possesses high dielectric permittivity and consists of an interpenetrating polymer network of silicone elastomer and ionic silicone species that are cross-linked through proton exchange between amines and acids. The ionically cross-linked silicone provides self-healing properties after electrical breakdown...... or cuts made directly to the material due to the reassembly of the ionic bonds that are broken during damage. The dielectric elastomers presented in this paper pave the way to increased lifetimes and the ability of dielectric elastomers to survive millions of cycles in high-voltage conditions....

  17. Dielectric behaviour of strontium tartrate single crystals

    Indian Academy of Sciences (India)

    Unknown

    dielectric loss (tan δ) as functions of frequency and temperature. Ion core type ... Since the data on dielectric properties of strontium tartrate trihydrate (STT) do not ... through 'AE' make 15-amp dimmerstat, the rate of heating was maintained ...

  18. Refractory oxides for fusion reactor first walls, the effects of the reducing environment

    International Nuclear Information System (INIS)

    Hoffman, J.G.

    1979-01-01

    Of the several applications for refractory oxides in fusion reactor systems, the most demanding is that for the first wall. Some components in proximity of the first wall (possibly waveguides or flux breakers) will also be subjected to similar environments. Many parameters affect the ultimate usability of a particular material for reactor applications: electrical resistivity and dielectric breakdown if applicable, thermal conductivity, mechanical properties, and stability with respect to neutral molecular or atomic, or ionized fuel gases. All these properties can be affected by the radiation environment present in an operating power reactor. Temperatures up to 2000K may be expected for radiatively cooled first wall liners in some proposed designs although surface temperatures are appreciably lower (approximately 1000K) in other applications. The exact nature of the chemical environment is not defined even for the most well developed design concepts, but possible environments may be hypothesized; ambient neutral molecular and atomic species, bombardment by high energy charge exchange neutral atoms, direct ionic bombardment from stray ions, and plasma dumps from failure of the confinement system. Preliminary work has begun to more adequately define the extent of the problem and suggest approaches to engineering solutions

  19. From surface to volume plasmons in hyperbolic metamaterials: General existence conditions for bulk high-k waves in metal-dielectric and graphene-dielectric multilayers

    DEFF Research Database (Denmark)

    Zhukovsky, Sergei; Andryieuski, Andrei; Sipe, John E.

    2014-01-01

    -dielectric and recently introduced graphene-dielectric stacks. We confirm that short-range surface plasmons in thin metal layers can give rise to hyperbolic metamaterial properties and demonstrate that long-range surface plasmons cannot. We also show that graphene-dielectric multilayers tend to support high- k waves...

  20. Collective focusing ion accelerator

    International Nuclear Information System (INIS)

    Goldin, F.J.

    1986-01-01

    The principal subject of this dissertation is the trapping confinement of pure electron plasmas in bumpy toroidal magnetic fields, with particular attention given to the trapping procedure and the behavior of the plasma during the final equilibrium. The most important aspects of the equilibrium studied were the qualitative nature of the plasma configuration and motion and its density, distribution and stability. The motivation for this study was that an unneutralized cloud of electrons contained in a toroidal system, sufficiently dense and stable, may serve to electrostatically focus ions (against centrifugal and self space charge forces) in a cyclic ion accelerator. Such an accelerator, known as a Collective Focusing Ion Accelerator (CFIA) could be far smaller than conventional designs (which use external magnetic fields directly to focus the ions) due to the smaller gyro-radium of an electron in a magnetic field of given strength. The electron cloud generally drifted poloidally at a finite radius from the toroidal minor axis. As this would preclude focusing ions with such clouds, damping this motion was investigated. Finite resistance in the normally perfectly conductive vessel wall did this. In further preparation for a working CFIA, additional experiments studied the effect of ions on the stability of the electron cloud

  1. Spectroscopy and Biosensing with Optically Resonant Dielectric Nanostructures

    OpenAIRE

    Krasnok, Alex; Caldarola, Martin; Bonod, Nicolas; Alú, Andrea

    2017-01-01

    Resonant dielectric nanoparticles (RDNs) made of materials with large positive dielectric permittivity, such as Si, GaP, GaAs, have become a powerful platform for modern light science, enabling various fascinating applications in nanophotonics and quantum optics. In addition to light localization at the nanoscale, dielectric nanostructures provide electric and magnetic resonant responses throughout the visible and infrared spectrum, low dissipative losses and optical heating, low doping effec...

  2. Materials Fundamentals of Gate Dielectrics

    CERN Document Server

    Demkov, Alexander A

    2006-01-01

    This book presents materials fundamentals of novel gate dielectrics that are being introduced into semiconductor manufacturing to ensure the continuous scalling of the CMOS devices. This is a very fast evolving field of research so we choose to focus on the basic understanding of the structure, thermodunamics, and electronic properties of these materials that determine their performance in device applications. Most of these materials are transition metal oxides. Ironically, the d-orbitals responsible for the high dielectric constant cause sever integration difficulties thus intrinsically limiting high-k dielectrics. Though new in the electronics industry many of these materials are wel known in the field of ceramics, and we describe this unique connection. The complexity of the structure-property relations in TM oxides makes the use of the state of the art first-principles calculations necessary. Several chapters give a detailed description of the modern theory of polarization, and heterojunction band discont...

  3. Dielectric function of semiconductor superlattice

    International Nuclear Information System (INIS)

    Qin Guoyi.

    1990-08-01

    We present a calculation of the dielectric function for semiconductor GaAs/Ga 1-x Al x As superlattice taking account of the extension of the electron envelope function and the difference of both the dielectric constant and width between GaAs and Ga 1-x Al x As layers. In the appropriate limits, our results exactly reduce to the well-known results of the quasi two-dimensional electron gas obtained by Lee and Spector and of the period array of two-dimensional electron layers obtained by Das Sarma and Quinn. By means of the dielectric function of the superlattice, the dispersion relation of the collective excitation and the screening property of semiconductor superlattice are discussed and compared with the results of the quasi two-dimensional system and with the results of the periodic array of the two-dimensional electron layers. (author). 4 refs, 3 figs

  4. Diffraction of an Electromagnetic Wave on a Dielectric Rod in a Rectangular Waveguide. A Method of Partial Waveguide Filling

    Science.gov (United States)

    Zav'yalov, A. S.

    2018-04-01

    A variant of the method of partial waveguide filling is considered in which a sample is put into a waveguide through holes in wide waveguide walls at the distance equal to a quarter of the wavelength in the waveguide from a short-circuiter, and the total input impedance of the sample in the waveguide is directly measured. The equivalent circuit of the sample is found both without and with account of the hole. It is demonstrated that consideration of the edge effect makes it possible to obtain more exact values of the dielectric permittivity.

  5. Dielectric elastomer actuators used for pneumatic valve technology

    International Nuclear Information System (INIS)

    Giousouf, Metin; Kovacs, Gabor

    2013-01-01

    Dielectric elastomer actuators have been investigated for applications in the field of pneumatic automation technology. We have developed different valve designs with stacked dielectric elastomer actuators and with integrated high voltage converters. The actuators were made using VHB-4910 material and a stacker machine for automated fabrication of the cylindrical actuators. Typical characteristics of pneumatic valves such as flow rate, power consumption and dynamic behaviour are presented. For valve construction the force and stroke parameters of the dielectric elastomer actuator have been measured. Further, benefits for valve applications using dielectric elastomers are shown as well as their potential operational area. Finally, challenges are discussed that are relevant for the use of elastomer actuators in valves for industrial applications. (paper)

  6. Dielectric relaxation studies of dilute solutions of amides

    Energy Technology Data Exchange (ETDEWEB)

    Malathi, M.; Sabesan, R.; Krishnan, S

    2003-11-15

    The dielectric constants and dielectric losses of formamide, acetamide, N-methyl acetamide, acetanilide and N,N-dimethyl acetamide in dilute solutions of 1,4-dioxan/benzene have been measured at 308 K using 9.37 GHz, dielectric relaxation set up. The relaxation time for the over all rotation {tau}{sub (1)} and that for the group rotation {tau}{sub (2)} of (the molecules were determined using Higasi's method. The activation energies for the processes of dielectric relaxation and viscous flow were determined by using Eyring's rate theory. From relaxation time behaviour of amides in non-polar solvent, solute-solvent and solute-solute type of molecular association is proposed.

  7. Temperature dependence of the dielectric properties of rubber wood

    Science.gov (United States)

    Mohammed Firoz Kabir; Wan M. Daud; Kaida B. Khalid; Haji A.A. Sidek

    2001-01-01

    The effect of temperature on the dielectric properties of rubber wood was investigated in three anisotropic directions—longitudinal, radial, and tangential, and at different measurement frequencies. Low frequency measurements were conducted with a dielectric spectrometer, and high frequencies used microwave applied with open-ended coaxial probe sensors. Dielectric...

  8. Preparation and Characterization of Pure Organic Dielectric Composites for Capacitors

    Directory of Open Access Journals (Sweden)

    Mao Xin

    2018-01-01

    Full Text Available This work reports the excellent dielectric composites were prepared from polyimide (PI and poly(vinylidene fluoride (PVDF via solution blending and thermal imidization or chemical imidization. The dielectric and thermal properties of the composites were studied. Results indicated that the dielectric properties of the composites synthesized by these two methods were enhanced through the introduction of PVDF, and the composites exhibited excellent thermal stability. Compared to the thermal imidization, the composites prepared by chemical imidization exhibited superior dielectric properties. This study demonstrated that the PI/PVDF composites were potential dielectric materials in the field of electronics.

  9. Dielectric polarization in random media

    International Nuclear Information System (INIS)

    Ramshaw, J.D.

    1984-01-01

    The theory of dielectric polarization in random media is systematically formulated in terms of response kernels. The primary response kernel K(12) governs the mean dielectric response at the point r 1 to the external electric field at the point r 2 in an infinite system. The inverse of K(12) is denoted by L(12);. it is simpler and more fundamental than K(12) itself. Rigorous expressions are obtained for the effective dielectric constant epsilon( in terms of L(12) and K(12). The latter expression involves the Onsger-Kirkwood function (epsilon(-epsilon 0 (2epsilon(+epsilon 0 )/epsilon 0 epsilon( (where epsilon 0 is an arbitrary reference value), and appears to be new to the random medium context. A wide variety of series representations for epsilon( are generated by means of general perturbation expansions for K(12) and L(12). A discussion is given of certain pitfalls in the theory, most of which are related to the fact that the response kernels are long ranged. It is shown how the dielectric behavior of nonpolar molecular fluids may be treated as a special case of the general theory. The present results for epsilon( apply equally well to other effective phenomenological coefficients of the same generic type, such as thermal and electrical conductivity, magnetic susceptibility, and diffusion coefficients

  10. Laser power sources and laser technology for accelerators

    International Nuclear Information System (INIS)

    Lowenthal, D.

    1986-01-01

    The requirements on laser power sources for advanced accelerator concepts are formidable. These requirements are driven by the need to deliver 5 TeV particles at luminosities of 10/sup 33/ - 10/sup 34/ cm/sup -2/ sec/sup -1/. Given that optical power can be transferred efficiently to the particles these accelerator parameters translate into single pulse laser output energies of several kilojoules and rep rates of 1-10 kHz. The average laser output power is then 10-20 MW. Larger average powers will be needed if efficient transfer proves not to be possible. A laser plant of this magnitude underscores the importance of high wall plug efficiency and reasonable cost in $/Watt. The interface between the laser output pulse format and the accelerator structure is another area that drives the laser requirements. Laser accelerators break up into two general architectures depending on the strength of the laser coupling. For strong coupling mechanisms, the architecture requires many ''small'' lasers powering the accelerator in a staged arrangement. For the weak coupling mechanisms, the architecture must feature a single large laser system whose power must be transported along the entire accelerator length. Both of these arrangements have demanding optical constraints in terms of phase matching sequential stages, beam combining arrays of laser outputs and optimizing coupling of laser power in a single accelerating stage

  11. High temperature polymer film dielectrics for aerospace power conditioning capacitor applications

    Energy Technology Data Exchange (ETDEWEB)

    Venkat, Narayanan, E-mail: venkats3@gmail.co [University of Dayton Research Institute (UDRI), Dayton, OH 45469 (United States); Dang, Thuy D. [Air Force Research Laboratory-Nanostructured and Biological Materials Branch (AFRL/RXBN) (United States); Bai Zongwu; McNier, Victor K. [University of Dayton Research Institute (UDRI), Dayton, OH 45469 (United States); DeCerbo, Jennifer N. [Air Force Research Laboratory-Electrical Technology Branch (AFRL/RZPE), Wright-Patterson Air Force Base, OH 45433 (United States); Tsao, B.-H. [University of Dayton Research Institute (UDRI), Dayton, OH 45469 (United States); Stricker, Jeffery T. [Air Force Research Laboratory-Electrical Technology Branch (AFRL/RZPE), Wright-Patterson Air Force Base, OH 45433 (United States)

    2010-04-15

    Polymer dielectrics are the preferred materials of choice for capacitive energy-storage applications because of their potential for high dielectric breakdown strengths, low dissipation factors and good dielectric stability over a wide range of frequencies and temperatures, despite having inherently lower dielectric constants relative to ceramic dielectrics. They are also amenable to large area processing into films at a relatively lower cost. Air Force currently has a strong need for the development of compact capacitors which are thermally robust for operation in a variety of aerospace power conditioning applications. While such applications typically use polycarbonate (PC) dielectric films in wound capacitors for operation from -55 deg. C to 125 deg. C, future power electronic systems would require the use of polymer dielectrics that can reliably operate up to elevated temperatures in the range of 250-350 deg. C. The focus of this research is the generation and dielectric evaluation of metallized, thin free-standing films derived from high temperature polymer structures such as fluorinated polybenzoxazoles, post-functionalized fluorinated polyimides and fluorenyl polyesters incorporating diamond-like hydrocarbon units. The discussion is centered mainly on variable temperature dielectric measurements of film capacitance and dissipation factor and the effects of thermal cycling, up to a maximum temperature of 350 deg. C, on film dielectric performance. Initial studies clearly point to the dielectric stability of these films for high temperature power conditioning applications, as indicated by their relatively low temperature coefficient of capacitance (TCC) (approx2%) over the entire range of temperatures. Some of the films were also found to exhibit good dielectric breakdown strengths (up to 470 V/mum) and a film dissipation factor of the order of <0.003 (0.3%) at the frequency of interest (10 kHz) for the intended applications. The measured relative dielectric

  12. Plasma polymerized high energy density dielectric films for capacitors

    Science.gov (United States)

    Yamagishi, F. G.

    1983-01-01

    High energy density polymeric dielectric films were prepared by plasma polymerization of a variety of gaseous monomers. This technique gives thin, reproducible, pinhole free, conformable, adherent, and insoluble coatings and overcomes the processing problems found in the preparation of thin films with bulk polymers. Thus, devices are prepared completely in a vacuum environment. The plasma polymerized films prepared all showed dielectric strengths of greater than 1000 kV/cm and in some cases values of greater than 4000 kV/cm were observed. The dielectric loss of all films was generally less than 1% at frequencies below 10 kHz, but this value increased at higher frequencies. All films were self healing. The dielectric strength was a function of the polymerization technique, whereas the dielectric constant varied with the structure of the starting material. Because of the thin films used (thickness in the submicron range) surface smoothness of the metal electrodes was found to be critical in obtaining high dielectric strengths. High dielectric strength graft copolymers were also prepared. Plasma polymerized ethane was found to be thermally stable up to 150 C in the presence of air and 250 C in the absence of air. No glass transitions were observed for this material.

  13. Millimeter wave and terahertz dielectric properties of biological materials

    Science.gov (United States)

    Khan, Usman Ansar

    Broadband dielectric properties of materials can be employed to identify, detect, and characterize materials through their unique spectral signatures. In this study, millimeter wave, submillimeter wave, and terahertz dielectric properties of biological substances inclusive of liquids, solids, and powders were obtained using Dispersive Fourier Transform Spectroscopy (DFTS). Two broadband polarizing interferometers were constructed to test materials from 60 GHz to 1.2 THz. This is an extremely difficult portion of the frequency spectrum to obtain a material's dielectric properties since neither optical nor microwave-based techniques provide accurate data. The dielectric characteristics of liquids such as cyclohexane, chlorobenzene, benzene, ethanol, methanol, 1,4 dioxane, and 10% formalin were obtained using the liquid interferometer. Subsequently the solid interferometer was utilized to determine the dielectric properties of human breast tissues, which are fixed and preserved in 10% formalin. This joint collaboration with the Tufts New England Medical Center demonstrated a significant difference between the dielectric response of tumorous and non-tumorous breast tissues across the spectrum. Powders such as anthrax, flour, talc, corn starch, dry milk, and baking soda have been involved in a number of security threats and false alarms around the globe in the last decade. To be able to differentiate hoax attacks and serious security threats, the dielectric properties of common household powders were also examined using the solid interferometer to identify the powders' unique resonance peaks. A new sample preparation kit was designed to test the powder specimens. It was anticipated that millimeter wave and terahertz dielectric characterization will enable one to clearly distinguish one powder from the other; however most of the powders had relatively close dielectric responses and only Talc had a resonance signature recorded at 1.135 THz. Furthermore, due to

  14. Bioactive surface modifications on inner walls of poly-tetra-fluoro-ethylene tubes using dielectric barrier discharge

    Science.gov (United States)

    Cho, Yong Ki; Park, Daewon; Kim, Hoonbae; Lee, Hyerim; Park, Heonyong; Kim, Hong Ja; Jung, Donggeun

    2014-03-01

    Bioactive surface modification can be used in a variety of medical polymeric materials in the fields of biochips and biosensors, artificial membranes, and vascular grafts. In this study, the surface modification of the inner walls of poly-tetra-fluoro-ethylene (PTFE) tubing was carried out to improve vascular grafts, which are made of biocompatible material for the human body in the medical field. Focus was centered on the cell attachment of the inner wall of the PTFE by sequential processes of hydrogen plasma treatment, hydrocarbon deposition, and reactive plasma treatment on the PFTE surface using micro plasma discharge. Micro plasma was generated by a medium-frequency alternating current high-voltage generator. The preliminary modification of PTFE was conducted by a plasma of hydrogen and argon gases. The hydrocarbon thin film was deposited on modified PTFE with a mixture of acetylene and argon gases. The reactive plasma treatment using oxygen plasma was done to give biocompatible functionality to the inner wall surface. The hydrophobic surface of bare PTFE is made hydrophilic by the reactive plasma treatment due to the formation of carbonyl groups on the surface. The reactive treatment could lead to improved attachment of smooth muscle cells (SMCs) on the modified PTFE tubing. Fourier transform infrared absorption spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and water contact angle measurement were used for the analysis of the surface modification. The SMC-attached PTFE tube developed will be applicable to in vitro human vasculature-mimetic model systems, and to medical vascular grafts.

  15. Dielectric behaviour of erbium substituted Mn–Zn ferrites

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Dielectric properties such as dielectric constant (ε′) and dielectric loss tangent (tan δ) of mixed. Mn–Zn–Er ferrites having the compositional formula Mn0⋅58Zn0⋅37Fe2⋅05–xErxO4 (where x = 0⋅2, 0⋅4, 0⋅6, 0⋅8 and. 1⋅0) were measured at room temperature in the frequency range 1–13 MHz using a HP ...

  16. Linear electron accelerator body and method of its manufacture

    International Nuclear Information System (INIS)

    Landa, V.; Maresova, V.; Lucek, J.; Prusa, F.

    1988-01-01

    The accelerator body consists of a hollow casing made of a high electric conductivity metal. The inside is partitioned with a system of resonators. The resonator body is made of one piece of the same metal as the casing or a related one (e.g., copper -coper, silver-copper, copper-copper alloy). The accelerator body is manufactured using the cathodic process on the periphery of a system of metal partitions and negative models of resonator cavities fitted to a metal pin. The pin is then removed from the system and the soluble models of the cavities are dissolved in a solvent. The advantage of the design and the method of manufacture is that the result is a compact, perfectly tight body with a perfectly lustre surface. The casing wall can be very thin, which improves accelerator performance. The claimed method can also be used in manufacturing miniature accelerators. (E.J.). 1 fig

  17. Three-dimensional periodic dielectric structures having photonic Dirac points

    Science.gov (United States)

    Bravo-Abad, Jorge; Joannopoulos, John D.; Soljacic, Marin

    2015-06-02

    The dielectric, three-dimensional photonic materials disclosed herein feature Dirac-like dispersion in quasi-two-dimensional systems. Embodiments include a face-centered cubic (fcc) structure formed by alternating layers of dielectric rods and dielectric slabs patterned with holes on respective triangular lattices. This fcc structure also includes a defect layer, which may comprise either dielectric rods or a dielectric slab with patterned with holes. This defect layer introduces Dirac cone dispersion into the fcc structure's photonic band structure. Examples of these fcc structures enable enhancement of the spontaneous emission coupling efficiency (the .beta.-factor) over large areas, contrary to the conventional wisdom that the .beta.-factor degrades as the system's size increases. These results enable large-area, low-threshold lasers; single-photon sources; quantum information processing devices; and energy harvesting systems.

  18. PLZT capacitor and method to increase the dielectric constant

    Science.gov (United States)

    Taylor, Ralph S.; Fairchild, Manuel Ray; Balachjandran, Uthamalingam; Lee, Tae H.

    2017-12-12

    A ceramic-capacitor includes a first electrically-conductive-layer, a second electrically-conductive-layer arranged proximate to the first electrically-conductive-layer, and a dielectric-layer interposed between the first electrically-conductive-layer and the second electrically-conductive-layer. The dielectric-layer is formed of a lead-lanthanum-zirconium-titanate material (PLZT), wherein the PLZT is characterized by a dielectric-constant greater than 125, when measured at 25 degrees Celsius and zero Volts bias, and an excitation frequency of ten-thousand Hertz (10 kHz). A method for increasing a dielectric constant of the lead-lanthanum-zirconium-titanate material (PLZT) includes the steps of depositing PLZT to form a dielectric-layer of a ceramic-capacitor, and heating the ceramic-capacitor to a temperature not greater than 300.degree. C.

  19. Three-dimensional periodic dielectric structures having photonic Dirac points

    Energy Technology Data Exchange (ETDEWEB)

    Bravo-Abad, Jorge; Joannopoulos, John D.; Soljacic, Marin

    2015-06-02

    The dielectric, three-dimensional photonic materials disclosed herein feature Dirac-like dispersion in quasi-two-dimensional systems. Embodiments include a face-centered cubic (fcc) structure formed by alternating layers of dielectric rods and dielectric slabs patterned with holes on respective triangular lattices. This fcc structure also includes a defect layer, which may comprise either dielectric rods or a dielectric slab with patterned with holes. This defect layer introduces Dirac cone dispersion into the fcc structure's photonic band structure. Examples of these fcc structures enable enhancement of the spontaneous emission coupling efficiency (the .beta.-factor) over large areas, contrary to the conventional wisdom that the .beta.-factor degrades as the system's size increases. These results enable large-area, low-threshold lasers; single-photon sources; quantum information processing devices; and energy harvesting systems.

  20. Experimental Characterization of Dielectric Properties in Fluid Saturated Artificial Shales

    OpenAIRE

    Beloborodov, Roman; Pervukhina, Marina; Han, Tongcheng; Josh, Matthew

    2017-01-01

    High dielectric contrast between water and hydrocarbons provides a useful method for distinguishing between producible layers of reservoir rocks and surrounding media. Dielectric response at high frequencies is related to the moisture content of rocks. Correlations between the dielectric permittivity and specific surface area can be used for the estimation of elastic and geomechanical properties of rocks. Knowledge of dielectric loss-factor and relaxation frequency in shales is critical for t...

  1. A study on the shell wall thinning causes identified through experiment, numerical analysis and ultrasonic test of high-pressure feedwater heater

    International Nuclear Information System (INIS)

    Hwang, Kyeong Mo; Woo, Lee; Jin, Tae Eun; Kim, Kyung Hoon

    2008-01-01

    Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which accelerates as the operation progresses. Several nuclear power plants in Korea have undergone this damage around the impingement baffle - installed downstream of the high-pressure turbine extraction steam line - inside numbers 5A and 5B feedwater heaters. At that point, the extracted steam from the high-pressure turbine consists in the form of two-phase fluid at high temperature, high pressure and high velocity. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of number 5 high-pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes the comparisons between the numerical analysis results using the FLUENT code and the downscaled experimental data in an effort to determine root causes of the shell wall thinning of the high-pressure feedwater heaters. The numerical analysis and experimental data were also confirmed by the actual wall thickness measured by ultrasonic tests. From the comparison of the results for the local velocity profiles and the wall thinning measurements, the local velocity component only in the y-direction flowing vertically to the shell wall, and not in the x- and z-directions, was analogous to the wall thinning data

  2. Slots in dielectric image line as mode launchers and circuit elements

    Science.gov (United States)

    Solbach, K.

    1981-01-01

    A planar resonator model is used to investigate slots in the ground plane of dielectric image lines. An equivalent circuit representation of the slot discontinuity is obtained, and the launching efficiency of the slot as a mode launcher is analyzed. Slots are also shown to be useful in the realization of dielectric image line array antennas. It is found that the slot discontinuity can be shown as a T-junction of the dielectric image line and a metal waveguide. The launching efficiency is found to increase with the dielectric constant of the dielectric image line, exhibiting a maximum value for guides whose height is slightly less than half a wavelength in the dielectric medium. The measured launching efficiencies of low permittivity dielectric image lines are found to be in good agreement with calculated values

  3. Dielectric and photo-dielectric properties of TlGaSeS crystals

    Indian Academy of Sciences (India)

    Administrator

    cDepartment of Physics, Middle East Technical University, 06800 Ankara, Turkey. MS received ... The crystals are observed to exhibit a dark high frequency effective dielectric constant value of ~ 10\\65 x ... communication systems. Keywords.

  4. Full Polymer Dielectric Elastomeric Actuators (DEA Functionalised with Carbon Nanotubes and High-K Ceramics

    Directory of Open Access Journals (Sweden)

    Tilo Köckritz

    2016-09-01

    Full Text Available Dielectric elastomer actuators (DEA are special devices which have a simple working and construction principle and outstanding actuation properties. The DEAs consist of a combination of different materials for the dielectric and electrode layers. The combination of these layers causes incompatibilities in their interconnections. Dramatic differences in the mechanical properties and bad adhesion of the layers are the principal causes for the reduction of the actuation displacement and strong reduction of lifetime. Common DEAs achieve actuation displacements of 2% and a durability of some million cycles. The following investigations represent a new approach to solving the problems of common systems. The investigated DEA consists of only one basic raw polymer, which was modified according to the required demands of each layer. The basic raw polymer was modified with single-walled carbon nanotubes or high-k ceramics, for example, lead magnesium niobate-lead titanate. The development of the full polymer DEA comprised the development of materials and technologies to realise a reproducible layer composition. It was proven that the full polymer actuator worked according to the theoretical rules. The investigated system achieved actuation displacements above 20% regarding thickness, outstanding interconnections at each layer without any failures, and durability above 3 million cycles without any indication of an impending malfunction.

  5. H.V. support structure of 3MVDC generator and its protection from HV discharges in vacuum and SF6 gas for DC electron accelerator

    International Nuclear Information System (INIS)

    Sharma, D.K.; Rajan, R.N.; Srivastava, S.K.; Dewangan, S.; Jayaprakash, D.; Bakhtsingh, R.I.; Acharya, S.; Gantayet, L.M.

    2014-01-01

    Accelerator and Pulse Power Division of BARC has developed a DC electron accelerator for cross linking of polymers, medical sterilisation, preservation of food. The demonstration of stack-gas cleanup for green power generation has been demonstrated successfully. The support structure of the 3MVDC voltage generator is made of Perspex for high dielectric strength, easy availability of raw material, excellent radiation resistance and long term dimensional stability. This paper describes the salient design features of the High voltage support structure in brief. (author)

  6. H.V. support structure of 3MVDC generator and its protection from HV discharges in vacuum and SF6 gas for DC electron accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, D.K.; Rajan, R.N.; Srivastava, S.K.; Dewangan, S.; Jayaprakash, D.; Bakhtsingh, R.I.; Acharya, S.; Gantayet, L.M., E-mail: dksharma@barc.gov.in [Accelerator and Pulse Power Division, Bhabha Atomic Research Centre, Mumbai (India)

    2014-07-01

    Accelerator and Pulse Power Division of BARC has developed a DC electron accelerator for cross linking of polymers, medical sterilisation, preservation of food. The demonstration of stack-gas cleanup for green power generation has been demonstrated successfully. The support structure of the 3MVDC voltage generator is made of Perspex for high dielectric strength, easy availability of raw material, excellent radiation resistance and long term dimensional stability. This paper describes the salient design features of the High voltage support structure in brief. (author)

  7. Energy storage in ceramic dielectrics

    International Nuclear Information System (INIS)

    Love, G.R.

    1990-01-01

    Historically, multilayer ceramic capacitors (MLC's) have not been considered for energy storage applications for two primary reasons. First, physically large ceramic capacitors were very expensive and, second, total energy density obtainable was not nearly so high as in electrolytic capacitor types. More recently, the fabrication technology for MLC's has improved significantly, permitting both significantly higher energy density and significantly lower costs. Simultaneously, in many applications, total energy storage has become smaller, and the secondary requirements of very low effective series resistance and effective series inductance (which, together, determine how efficiently the energy may be stored and recovered) have become more important. It is therefore desirable to reexamine energy storage in ceramics for contemporary commercial and near-commercial dielectrics. Stored energy is proportional to voltage squared only in the case of paraelectric insulators, because only they have capacitance that is independent of bias voltage. High dielectric constant materials, however, are ferroics (that is ferroelectric and/or antiferroelectric) and display significant variation of effective dielectric constant with bias voltage

  8. Electrostatic field in inhomogeneous dielectric media. I. Indirect boundary element method

    International Nuclear Information System (INIS)

    Goel, N.S.; Gang, F.; Ko, Z.

    1995-01-01

    A computationally fast method is presented for calculating electrostatic field in arbitrary inhomogeneous dielectric media with open boundary condition. The method involves dividing the whole space into cubical cells and then finding effective dielectric parameters for interfacial cells consisting of several dielectrics. The electrostatic problem is then solved using either the indirect boundary element method described in this paper or the so-called volume element method described in the companion paper. Both methods are tested for accuracy by comparing the numerically calculated electrostatic fields against those analytically obtained for a dielectric sphere and dielectric ellipsoid in a uniform field and for a dielectric sphere in a point charge field

  9. A Flexible Capacitive Sensor with Encapsulated Liquids as Dielectrics

    Directory of Open Access Journals (Sweden)

    Yasunari Hotta

    2012-03-01

    Full Text Available Flexible and high-sensitive capacitive sensors are demanded to detect pressure distribution and/or tactile information on a curved surface, hence, wide varieties of polymer-based flexible MEMS sensors have been developed. High-sensitivity may be achieved by increasing the capacitance of the sensor using solid dielectric material while it deteriorates the flexibility. Using air as the dielectric, to maintain the flexibility, sacrifices the sensor sensitivity. In this paper, we demonstrate flexible and highly sensitive capacitive sensor arrays that encapsulate highly dielectric liquids as the dielectric. Deionized water and glycerin, which have relative dielectric constants of approximately 80 and 47, respectively, could increase the capacitance of the sensor when used as the dielectric while maintaining flexibility of the sensor with electrodes patterned on flexible polymer substrates. A reservoir of liquids between the electrodes was designed to have a leak path, which allows the sensor to deform despite of the incompressibility of the encapsulated liquids. The proposed sensor was microfabricated and demonstrated successfully to have a five times greater sensitivity than sensors that use air as the dielectric.

  10. Vegetable oil based liquid nanocomposite dielectric

    Directory of Open Access Journals (Sweden)

    Leon Chetty

    2013-01-01

    Full Text Available Physically smaller dielectric materials would improve the optimisation of space for power systems. Development of nanotechnology provides an effective way to improve the performances of insulating oils used in power system applications. In this research study, we focused on the development of nanomodified vegetable oils to be used in power transformers. Higher conduction currents were observed in virgin linseed oil than in virgin castor oil. However, for both virgin linseed and virgin castor oil, the DC conduction current increased approximately linearly with the applied DC voltage. In nanomodified linseed oil, the characteristic curve showed two distinct regions: a linear region (at lower applied voltage and a saturation region (at slightly higher voltage. Conversely, in nanomodified castor oil, the characteristic curve showed three distinct regions: a linear region (at lower applied voltage, a saturation region (at intermediate applied voltage and an exponential growth region (at higher applied voltage. The nanomodified linseed oil exhibited a better dielectric performance than the nanomodified castor oil. Overall, the addition of nanodielectrics to vegetable oils decreased the dielectric performance of the vegetable oils. The results of this study contribute to the understanding of the pre-breakdown phenomenon in liquid nanocomposite dielectrics.

  11. Effect of paramagnetic manganese ions doping on frequency and high temperature dependence dielectric response of layered Na1.9Li0.1Ti3O7 ceramics

    International Nuclear Information System (INIS)

    Pal, Dharmendra; Pandey, J.L.

    2010-01-01

    The manganese doped layered ceramic samples (Na 1.9 Li 0.1 )Ti 3 O 7 : XMn (0.01 ≤ X ≤ 0.1) have been prepared using high temperature solid state reaction. The room temperature electron paramagnetic resonance (EPR) investigations exhibit that at lower percentage of doping the substitution of manganese ions occur as Mn 3+ at Ti 4+ sites, whereas for higher percentage of doping Mn 2+ ions occupy the two different interlayer sodium/lithium sites. In both cases, the charge compensation mechanism should operate to maintain the overall charge neutrality of the lattice. The manganese doped derivatives of layered Na 1.9 Li 0. 1Ti 3 O 7 (SLT) ceramics have been investigated through frequency dependence dielectric spectroscopy in this work. The results indicate that the dielectric losses in these ceramics are the collective contribution of electric conduction, dipole orientation and space charge polarization. Smeared peaks in temperature dependence of permittivity plots suggest diffuse nature of high temperature ferroelectric phase transition. The light manganese doping in SLT enhances the dielectric constant. However, manganese doping decreases dielectric loss due to inhibition of domain wall motion, enhances electron-hopping conduction, and impedes the interlayer ionic conduction as well. Manganese doping also gives rise to contraction of interlayer space. (author)

  12. Effect of deformation and dielectric filling on electromagnetic ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    great significance in the development of microwave communication networks and ... media. Rectangular dielectric waveguide structures are analysed by Bierwirth ..... Schweig E, Bridges W B 1984 Computer analysis of dielectric waveguide: A ...

  13. Thermally stimulated discharge current (TSDC) and dielectric ...

    Indian Academy of Sciences (India)

    Unknown

    2001-10-09

    Oct 9, 2001 ... Measurements of TSDC and dielectric constant, ε′, have been ... Keywords. Semiconducting glass; TSDC; trap energy; dielectric constant. 1. ... determination of mean depth of the internal charge, activation ... thermal charging, viz. (i) internal ... the basis of d.c. conductivity and short range Na+ ion motion.

  14. Flame Acceleration and Transition to Detonation in High Speed Turbulent Combustion

    Science.gov (United States)

    2016-12-21

    Contract number N000141410177 for the time period December 31, 2013- December 31 , 2016 Principal Investigator: Elaine S. Oran Co-Investigator: Norman ...channel shown. (a) Rough walls generate turbulence. Flame ( green ) accelerates as it propagates down the channel. (b) DDT in the boundary layer near t

  15. 7th International Symposium on Gaseous Dielectrics

    CERN Document Server

    James, David

    1994-01-01

    The Seventh International Symposium on Gaseous Dielectrics was held in Knoxville, Tennessee, U. S. A. , on April 24-28, 1994. The symposium continued the interdisciplinary character and comprehensive approach of the preceding six symposia. Gaseous DielecIries VII is a detailed record of the symposium proceedings. It covers recent advances and developments in a wide range of basic, applied and industrial areas of gaseous dielectrics. It is hoped that Gaseous DielecIries VII will aid future research and development in, and encourage wider industrial use of, gaseous dielectrics. The Organizing Committee of the Seventh International Symposium on Gaseous Dielectrics consisted of G. Addis (U. S. A. ), L. G. Christophorou (U. S. A. ), F. Y. Chu (Canada), A. H. Cookson (U. S. A. ), O. Farish (U. K. ), I. Gallimberti (Italy) , A. Garscadden (U. S. A. ), D. R. James (U. S. A. ), E. Marode (France), T. Nitta (Japan), W. Pfeiffer (Germany), Y. Qiu (China), I. Sauers (U. S. A. ), R. J. Van Brunt (U. S. A. ), and W. Zaengl...

  16. Dielectric relaxation in AgI doped silver selenomolybdate glasses

    Science.gov (United States)

    Palui, A.; Shaw, A.; Ghosh, A.

    2016-05-01

    We report the study of dielectric properties of some silver ion conducting silver selenomolybdate mixed network former glasses in a wide frequency and temperature range. The experimental data have been analyzed in the framework of complex dielectric permittivity. The dielectric permittivity data have been well interpreted using the Cole-Cole function. The temperature dependence of relaxation time obtained from real part of dielectric permittivity data shows an Arrhenius behavior. The activation energy shows a decreasing trend with the increase of doping content. Values of stretched exponential parameter are observed to be independent of temperature and composition.

  17. Combined Mini-Cylex & Disk Acceleration Tests in Type K Copper.

    Energy Technology Data Exchange (ETDEWEB)

    Maines, Warren Russell [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kittell, David E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hobbs, Michael L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-12-01

    We combined the miniature cylinder expansion test (Mini-Cylex), with the Disk Acceleration Test (DAX) using Type K copper, Picatinny Liquid Explosive, and photonic Doppler velocimetry. We estimated the CJ state using plate reverberation methods at the test cap. We extracted velocities at 2, 7, and 10 volume expansions to fit Jones-Wilkins-Lee Equation of State at the tube wall. And we estimated Gurney velocity both at the test cap and tube wall. Our experiments and simulations are within expected uncertainty. The test and the analysis effectively reduce costs while keeping similar fidelity compared with more expensive tests.

  18. Method to characterize dielectric properties of powdery substances

    Science.gov (United States)

    Tuhkala, M.; Juuti, J.; Jantunen, H.

    2013-07-01

    An open ended coaxial cavity method for dielectric characterization of powdery substance operating at 4.5 GHz in TEM mode is presented. Classical mixing rules and electromagnetic modeling were utilized with measured effective permittivities and Q factors to determine the relative permittivity and dielectric loss tangent of different powders with ɛr up to 30. The modeling enabled determination of the correction factor for the simplified equation for the relative permittivity of an open ended coaxial resonator and mixing rules having the best correlation with experiments. SiO2, Al2O3, LTCC CT 2000, ZrO2, and La2O3 powders were used in the experiments. Based on the measured properties and Bruggeman symmetric and Looyenga mixing rules, the determined dielectric characteristics of the powders exhibited good correlation with values in the literature. The presented characterization method enabled the determination of dielectric properties of powdery substances within the presented range, and therefore could be applied to various research fields and applications where dielectric properties of powders need to be known and controlled.

  19. Dielectric platforms for surface-enhanced spectroscopies (Conference Presentation)

    Science.gov (United States)

    Maier, Stefan A.

    2016-03-01

    Plasmonic nanostructures serve as the main backbone of surface enhanced sensing methodologies, yet the associated optical losses lead to localized heating as well as quenching of molecules, complicating their use for enhancement of fluorescent emission. Additionally, conventional plasmonic materials are limited to operation in the visible part of the spectrum. We will elucidate how nanostructures consisting of conventional and polar dielectrics can be employed as a highly promising alternative platform. Dielectric nanostructures can sustain scattering resonances due to both electric and magnetic Mie modes. We have recently predicted high enhanced local electromagnetic field hot spots in dielectric nanoantenna dimers, with the hallmark of spot sizes comparable to those achievable with plasmonic antennas, but with lower optical losses. Here, we will present first experimental evidence for both fluorescence and Raman enhancement in dielectric nanoantennas, including a direct determination of localized heating, and compare to conventional Au dimer antennas. The second part of the talk will focus on the mid-infrared regime of the electromagnetic spectrum, outlining possibilities for surface enhanced infrared absorption spectroscopy based on polar and hyperbolic dielectrics.

  20. Confinement in the color dielectric model

    International Nuclear Information System (INIS)

    Pirner, H.J.

    1990-01-01

    The paper consists of several parts. In Section 2, I give an introduction to the main physics of lattice gauge theory. Section 3 gives an outline of the colour dielectric model and first numerical results on the effective action after one block-spinning step. Section 4 reviews some new work on the generalization of the colour dielectric model to SU3 colour . (orig./HSI)

  1. Atomic layer deposition of dielectrics for carbon-based electronics

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J., E-mail: jiyoung.kim@utdallas.edu; Jandhyala, S.

    2013-11-01

    Carbon based nanomaterials like nanotubes and graphene have emerged as future generation electronic materials for device applications because of their interesting properties such as high-mobility and ability to carry high-current densities compared to conventional semiconductor materials like silicon. Therefore, there is a need to develop techniques to integrate robust gate dielectrics with high-quality interfaces for these materials in order to attain maximum performance. To date, a variety of methods including physical vapor deposition, atomic layer deposition (ALD), physical assembly among others have been employed in order to integrate dielectrics for carbon nanotube and graphene based field-effect transistors. Owing to the difficulty in wetting pristine surfaces of nanotubes and graphene, most of the ALD methods require a seeding technique involving non-covalent functionalization of their surfaces in order to nucleate dielectric growth while maintaining their intrinsic properties. A comprehensive review regarding the various dielectric integration schemes for emerging devices and their limitations with respect to ALD based methods along with a future outlook is provided. - Highlights: • We introduce various dielectric integration schemes for carbon-based devices. • Physical vapor deposition methods tend to degrade device performance. • Atomic layer deposition on pristine surfaces of graphene and nanotube is difficult. • We review different seeding techniques for atomic layer deposition of dielectrics. • Compare the performance of graphene top-gate devices with different dielectrics.

  2. Atomic layer deposition of dielectrics for carbon-based electronics

    International Nuclear Information System (INIS)

    Kim, J.; Jandhyala, S.

    2013-01-01

    Carbon based nanomaterials like nanotubes and graphene have emerged as future generation electronic materials for device applications because of their interesting properties such as high-mobility and ability to carry high-current densities compared to conventional semiconductor materials like silicon. Therefore, there is a need to develop techniques to integrate robust gate dielectrics with high-quality interfaces for these materials in order to attain maximum performance. To date, a variety of methods including physical vapor deposition, atomic layer deposition (ALD), physical assembly among others have been employed in order to integrate dielectrics for carbon nanotube and graphene based field-effect transistors. Owing to the difficulty in wetting pristine surfaces of nanotubes and graphene, most of the ALD methods require a seeding technique involving non-covalent functionalization of their surfaces in order to nucleate dielectric growth while maintaining their intrinsic properties. A comprehensive review regarding the various dielectric integration schemes for emerging devices and their limitations with respect to ALD based methods along with a future outlook is provided. - Highlights: • We introduce various dielectric integration schemes for carbon-based devices. • Physical vapor deposition methods tend to degrade device performance. • Atomic layer deposition on pristine surfaces of graphene and nanotube is difficult. • We review different seeding techniques for atomic layer deposition of dielectrics. • Compare the performance of graphene top-gate devices with different dielectrics

  3. Actuation response of polyacrylate dielectric elastomers

    DEFF Research Database (Denmark)

    Kofod, G.; Kornbluh, R.; Pelrine, R.

    2001-01-01

    Polyacrylate dielectric elastomers have yielded extremely large strain and elastic energy density suggesting that they are useful for many actuator applications. A thorough understanding of the physics underlying the mechanism of the observed response to an electric field can help develop improved......, though there are discrepancies. Further analysis suggests that these arise mostly from imperfect manufacture of the actuators, though there is a small contribution from an explicitly electrostrictive behavior of the acrylic adhesive. Measurements of the dielectric constant of stretched polymer reveal...... that the dielectric constant drops, when the polymer is strained, indicating the existence of a small electrostrictive effect. Finally, measurements of the electric breakdown field were made. These also show a dependence upon the strain. In the unstrained state the breakdown field is 20 WV/m, which grows to 218MV...

  4. Toward superlensing with metal-dielectric composites and multilayers

    DEFF Research Database (Denmark)

    Nielsen, Rasmus Bundgaard; Thoreson, M.D.; Chen, W.

    2010-01-01

    We report on the fabrication of two types of adjustable, near-field superlens designs: metal–dielectric composites and metal–dielectric multilayer films. We fabricated a variety of films with different materials, thicknesses and compositions. These samples were characterized physically...... and optically to determine their film composition, quality, and optical responses. Our results on metal–dielectric composites indicate that although the real part of the effective permittivity generally follows effective medium theory predictions, the imaginary part does not and substantially higher losses...

  5. Generation and confinement of microwave gas-plasma in photonic dielectric microstructure.

    Science.gov (United States)

    Debord, B; Jamier, R; Gérôme, F; Leroy, O; Boisse-Laporte, C; Leprince, P; Alves, L L; Benabid, F

    2013-10-21

    We report on a self-guided microwave surface-wave induced generation of ~60 μm diameter and 6 cm-long column of argon-plasma confined in the core of a hollow-core photonic crystal fiber. At gas pressure of 1 mbar, the micro-confined plasma exhibits a stable transverse profile with a maximum gas-temperature as high as 1300 ± 200 K, and a wall-temperature as low as 500 K, and an electron density level of 10¹⁴ cm⁻³. The fiber guided fluorescence emission presents strong Ar⁺ spectral lines in the visible and near UV. Theory shows that the observed combination of relatively low wall-temperature and high ionisation rate in this strongly confined configuration is due to an unprecedentedly wide electrostatic space-charge field and the subsequent ion acceleration dominance in the plasma-to-gas power transfer.

  6. Electrostatics of proteins in dielectric solvent continua. II. Hamiltonian reaction field dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Sebastian; Tavan, Paul; Mathias, Gerald, E-mail: gerald.mathias@physik.uni-muenchen.de [Lehrstuhl für BioMolekulare Optik, Ludig-Maximilians Universität München, Oettingenstr. 67, 80538 München (Germany)

    2014-03-14

    In Paper I of this work [S. Bauer, G. Mathias, and P. Tavan, J. Chem. Phys. 140, 104102 (2014)] we have presented a reaction field (RF) method, which accurately solves the Poisson equation for proteins embedded in dielectric solvent continua at a computational effort comparable to that of polarizable molecular mechanics (MM) force fields. Building upon these results, here we suggest a method for linearly scaling Hamiltonian RF/MM molecular dynamics (MD) simulations, which we call “Hamiltonian dielectric solvent” (HADES). First, we derive analytical expressions for the RF forces acting on the solute atoms. These forces properly account for all those conditions, which have to be self-consistently fulfilled by RF quantities introduced in Paper I. Next we provide details on the implementation, i.e., we show how our RF approach is combined with a fast multipole method and how the self-consistency iterations are accelerated by the use of the so-called direct inversion in the iterative subspace. Finally we demonstrate that the method and its implementation enable Hamiltonian, i.e., energy and momentum conserving HADES-MD, and compare in a sample application on Ac-Ala-NHMe the HADES-MD free energy landscape at 300 K with that obtained in Paper I by scanning of configurations and with one obtained from an explicit solvent simulation.

  7. Dielectric relaxation of selenium-tellurium mixed former glasses

    Science.gov (United States)

    Palui, A.; Ghosh, A.

    2017-05-01

    We report the study of dielectric properties of mixed network former glasses of composition 0.3Ag2O-0.7(xSeO2-(1-x)TeO2); x=0, 0.1, 0.3, 0.4, 0.5 and 0.6 in a wide frequency 10 Hz - 2 MHz and temperature range 223 K - 403 K. The experimental data have been analyzed in the framework of complex dielectric permittivity. The dielectric permittivity data have been analyzed using the Cole-Cole function. The inverse temperature dependence of relaxation time obtained from real part of dielectric permittivity data follows the Arrhenius relation. The activation energy shows mixed glass former effect with variation of mixed former ratio. A non-zero value of shape parameters is observed and it is almost independent of temperature and composition.

  8. Super soft silicone elastomers with high dielectric permittivity

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Hvilsted, Søren

    2015-01-01

    Dielectric elastomers (DEs) have many favourable properties. The obstacle of high driving voltages, however, limits the commercial viability of the technology at present. Driving voltage can be lowered by decreasing the Young’s modulus and increasing the dielectric permittivity of silicone...... elastomers. A decrease in Young’s modulus, however, is often accompanied by the loss of mechanical stability and thereby the lifetime of the DE. New soft elastomer matrices with high dielectric permittivity and low Young’s modulus, with no loss of mechanical stability, were prepared by two different...... approaches using chloropropyl-functional silicone polymers. The first approach was based on synthesised chloropropyl-functional copolymers that were cross-linkable and thereby formed the basis of new silicone networks with high dielectric permittivity (e.g. a 43% increase). These networks were soft without...

  9. The Dielectric Behavior of Cyano-Substituted Poly imides

    International Nuclear Information System (INIS)

    Elshazly, E.S.; Abdelrahman, A.A.M.; Elmasry, M.A.A.

    2013-01-01

    A number of amorphous poly imides containing polar functional groups, cyano group, have been synthesized and investigated for potential use as high temperature piezoelectric sensors. The piezoelectric constants are related to the polarization. The remanent polarization and hence piezoelectric response of a material is determined by dielectric relaxation strength which is the difference in dielectric constant at the glass transition temperature vicinity. The intent of this work is to clarify the mechanism and key components required for developing piezoelectricity in amorphous polymers and further to apply this understanding in designing a unique high temperature piezoelectric polyimide. In this paper, experimental investigations of dielectric constant of piezoelectric cyano -substituted poly imides have been tested as a function of temperature to measure the dielectric relaxation strength in the glass transition temperature region.

  10. Synthetic Strategies for High Dielectric Constant Silicone Elastomers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt

    synthetic strategies were developed in this Ph.D. thesis, in order to create silicone elastomers with high dielectric constants and thereby higher energy densities. The work focused on maintaining important properties such as dielectric loss, electrical breakdown strength and elastic modulus....... The methodology therefore involved chemically grafting high dielectric constant chemical groups onto the elastomer network, as this would potentially provide a stable elastomer system upon continued activation of the material. The first synthetic strategy involved the synthesis of a new type of cross...... extender’ that allowed for chemical modifications such as Cu- AAC. This route was promising for one-pot elastomer preparation and as a high dielectric constant additive to commercial silicone systems. The second approach used the borane-catalysed Piers-Rubinsztajn reaction to form spatially well...

  11. Bunch monitor for an S-band electron linear accelerator

    International Nuclear Information System (INIS)

    Otake, Yuji; Nakahara, Kazuo

    1991-01-01

    The measurement of bunch characteristics in an S-band electron linear accelerator is required in order to evaluate the quality of accelerated electron beams. A new-type bunch monitor has been developed which combines micro-stripline technology with an air insulator and wall-current monitoring technology. The obtained time resolution of the monitor was more than 150 ps. This result shows that the monitor can handle the bunch number of an S-band linac. The structure of the monitor is suitable for being installed in the vacuum area, since it is constructed of only metal and ceramic parts. It can therefore easily be employed in an actual machine

  12. Dielectric properties of hybrid perovskites and drift-diffusion modeling of perovskite cells

    Science.gov (United States)

    Pedesseau, L.; Kepenekian, M.; Sapori, D.; Huang, Y.; Rolland, A.; Beck, A.; Cornet, C.; Durand, O.; Wang, S.; Katan, C.; Even, J.

    2016-03-01

    A method based on DFT is used to obtained dielectric profiles. The high frequency Ɛ∞(z) and the static Ɛs(z) dielectric profiles are compared for 3D, 2D-3D and 2D Hybrid Organic Perovskites (HOP). A dielectric confinement is observed for the 2D materials between the high dielectric constant of the inorganic part and the low dielectric constant of the organic part. The effect of the ionic contribution on the dielectric constant is also shown. The quantum and dielectric confinements of 3D HOP nanoplatelets are then reported. Finally, a numerical simulation based on the SILVACO code of a HOP based solar cell is proposed for various permittivity of MAPbI3.

  13. Experimental determination of damping factors for walls of masonry and reinforced concrete

    International Nuclear Information System (INIS)

    Buttman, P.

    1983-01-01

    'Damping' is a fundamental parameter for the determination of the internal force with a given acceleration response spectrum when designing and dimensioning masonry and reinforced concrete walls for the loading case earthquake. The actual dampings of masonry and reinforced concrete walls are determined on a scale of 1:1 by means of a horizontal excitation at a chosen test setup. The test specimen have the dimensions b/h/d=100/200/11,5 cm and 24 cm. The horizontal and sinusoidal excitation of the test specimen is effected by a dynamic oscillating excitation with a maximum power of 20 kN. The evaluation of the measurements shows that the assumed damping values of 4% for the operating basis earthquake are realistic. In case of amplitudes corresponding to the loadings of the safe shutdown earthquake, however, dampings of 11% for reinforced concrete walls and of 24% for masonry walls were determined. This real damping behavior of reinforced concrete and masonry walls was documented by means of measurements, films and pictures. (orig.)

  14. The defects influence on domain wall propagation in bistable glass-coated microwires

    International Nuclear Information System (INIS)

    Rodionova, V.; Zhukova, V.; Ilyn, M.; Ipatov, M.; Perov, N.; Zhukov, A.

    2012-01-01

    We studied the domain wall (DW) dynamics of magnetically bistable amorphous glass-coated Fe 74 B 13 Si 11 C 2 microwires. In according to our experimental results magnetic field dependences of DW velocity of studied microwires can be divided into two groups: with uniform or uniformly accelerated DW propagation along the microwire. Strong correlation between the type of the magnetic field dependence of domain wall velocity, v(H), and the distribution of the local nucleation fields has been observed. Moreover, we observed abrupt increasing of DW velocity (jump) on the magnetic field dependences of the domain wall velocity, v(H), for the both types of the v(H) dependences. At the same time usual linear increasing of the domain wall velocity with magnetic field persists below these jumps. It was found that the jump height correlates with the location of nucleation place of the new domain wall. We have measured local nucleation field distribution in all the microwires. From local nucleation field distribution we have obtained the DW nucleation locations and estimated the jump height

  15. The defects influence on domain wall propagation in bistable glass-coated microwires

    Energy Technology Data Exchange (ETDEWEB)

    Rodionova, V. [Magnetism Division, Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Immanuel Kant Baltic Federal University, Kaliningrad 236041 (Russian Federation); Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU, San Sebastian 20018 (Spain); Zhukova, V., E-mail: valentina.zhukova@ehu.es [Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU, San Sebastian 20018 (Spain); Ilyn, M.; Ipatov, M. [Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU, San Sebastian 20018 (Spain); Perov, N. [Magnetism Division, Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Zhukov, A. [Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU, San Sebastian 20018 (Spain); IKERBASQUE, Basque Foundation for Science, Bilbao 48011 (Spain)

    2012-05-01

    We studied the domain wall (DW) dynamics of magnetically bistable amorphous glass-coated Fe{sub 74}B{sub 13}Si{sub 11}C{sub 2} microwires. In according to our experimental results magnetic field dependences of DW velocity of studied microwires can be divided into two groups: with uniform or uniformly accelerated DW propagation along the microwire. Strong correlation between the type of the magnetic field dependence of domain wall velocity, v(H), and the distribution of the local nucleation fields has been observed. Moreover, we observed abrupt increasing of DW velocity (jump) on the magnetic field dependences of the domain wall velocity, v(H), for the both types of the v(H) dependences. At the same time usual linear increasing of the domain wall velocity with magnetic field persists below these jumps. It was found that the jump height correlates with the location of nucleation place of the new domain wall. We have measured local nucleation field distribution in all the microwires. From local nucleation field distribution we have obtained the DW nucleation locations and estimated the jump height.

  16. Nanocomposite dielectrics-properties and implications

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, J K; Hu, Y [Department of Electrical, Computer and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States)

    2005-01-21

    The incorporation of nanoparticles into thermosetting resins is seen to impart desirable dielectric properties when compared with conventional (micron-sized particulates) composites. Although the improvements are accompanied by the mitigation of internal charge in the materials, the nature of the interfacial region is shown to be pivotal in determining the dielectric behaviour. In particular, it is shown that the conditions and enhanced area of the interface changes the bonding that may give rise to an interaction zone, which affects the interfacial polarization through the formation of local conductivity.

  17. Geometric phase from dielectric matrix

    International Nuclear Information System (INIS)

    Banerjee, D.

    2005-10-01

    The dielectric property of the anisotropic optical medium is found by considering the polarized photon as two component spinor of spherical harmonics. The Geometric Phase of a polarized photon has been evaluated in two ways: the phase two-form of the dielectric matrix through a twist and the Pancharatnam phase (GP) by changing the angular momentum of the incident polarized photon over a closed triangular path on the extended Poincare sphere. The helicity in connection with the spin angular momentum of the chiral photon plays the key role in developing these phase holonomies. (author)

  18. Features of dielectric response in PMN-PT ferroelectric ceramics

    International Nuclear Information System (INIS)

    Guerra, J D S; Araujo, E B; Guarany, C A; Reis, R N; Lima, E C

    2008-01-01

    In this paper, electrical and structural properties were reported for pyrochlore free (1 - x)[Pb(Mg 1/3 Nb 2/3 )O 3 ] - xPbTiO 3 (PMN-PT) (with 35 mol% PbTiO 3 ) ceramics obtained from fine powders. Dielectric studies were focused on the investigation of the complex dielectric permittivity (ε' - iε'') as a function of frequency and temperature. The effects of the dc applied electric field on dielectric response were also investigated. Results revealed a field dependence dielectric anomaly in the dielectric permittivity curves (ε(T)) in the low dc electric field region, which in turn prevails in the whole analysed frequency interval. To the best of our knowledge, these properties for the PMN-PT ceramic system have not been reported before as in this work. The results were analysed within the framework of the current models found in the literature.

  19. Defects in codoped NiO with gigantic dielectric response

    Science.gov (United States)

    Wu, Ping; Ligatchev, Valeri; Yu, Zhi Gen; Zheng, Jianwei; Sullivan, Michael B.; Zeng, Yingzhi

    2009-06-01

    We combine first-principles, statistical, and phenomenological methods to investigate the electronic and dielectric properties of NiO and clarify the nature of the gigantic dielectric response in codoped NiO. Unlike previous models which are dependent on grain-boundary effects, our model based on small polaron hopping in homogeneous material predicts the dielectric permittivity (104-5) for heavily Li- and MD -codoped NiO (MD=Ti,Al,Si) . Furthermore, we reproduce the experimental trends in dielectric properties as a function of the dopants nature and their concentrations, as well as the reported activation energies for the relaxation in Li- and Ti-codoped NiO (0.308 eV or 0.153 eV depending on the Fermi-level position). In this study, we demonstrate that small polaron hopping on dopant levels is the dominant mechanism for the gigantic dielectric response in these codoped NiO.

  20. Dielectric barrier discharges applied for soft ionization and their mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Brandt, Sebastian; Klute, Felix David; Schütz, Alexander; Franzke, Joachim, E-mail: joachim.franzke@isas.de

    2017-01-25

    Dielectric barrier discharges are used for analytical applications as dissociative source for optical emission spectrometry and for ambient-ionization techniques. In the range of ambient-ionization techniques it has attracted much attention in fields like food safety, biological analysis, mass spectrometry for reaction monitoring and imaging forensic identification. In this review some examples are given for the application as desorption/ionization source as well as for the sole application as ionization source with different sample introductions. It will be shown that the detection might depend on the certain distance of the plasma in reference to the sample or the kind of discharge which might be produced by different shapes of the applied high voltage. Some attempts of characterization are presented. A more detailed characterization of the dielectric barrier discharge realized with two ring electrodes, each separately covered with a dielectric layer, is described. - Highlights: • Dielectric barrier discharge applied as desorption/ionization source. • Dielectric barrier discharge applied solely as ionization source. • Different geometries in order to maintain soft ionization. • Characterization of the LTP probe. • Dielectric barrier discharges with two dielectric barriers (ring-ring shape).

  1. Dielectric properties of polycrystalline Cu-Zn ferrites at microwave frequencies

    International Nuclear Information System (INIS)

    Lamani, Ashok R.; Jayanna, H.S.; Parameswara, P.; Somashekar, R.; Ramachander,; Rao, Ramchandra; Prasanna, G.D.

    2011-01-01

    Highlights: → Cu 1-x Zn x Fe 2 O 4 at different concentration are suitable for high frequency applications. → Dielectric properties are related with W-H plot. → The anisotropy due to the crystallite size effect is significant in change of dielectric constant. - Abstract: The real dielectric constant ε' and complex dielectric constant ε'' of Cu 1-x Zn x Fe 2 O 4 have been measured at room temperature in the high frequency range 1 MHz to 1.8 GHz. At low frequencies the dielectric loss is found to be constant up to 1.4 GHz and there is a sudden rise at 1.5 GHz. A qualitative explanation is given for the composition, frequency dependence of the dielectric constant and dielectric loss of Cu 1-x Zn x Fe 2 O 4 . These are correlated with the W-H plot which gives the information about change in the average crystal size and strain of the samples. The micro-morphological features of the samples were obtained by Scanning Electron Microscopy (SEM). The micrograph shows that the increase of the Zn content in Cu ferrite increases the grain size.

  2. Tritium depth profiling in carbon by accelerator mass spectrometry

    International Nuclear Information System (INIS)

    Friedrich, M.; Pilz, W.; Sun, G.; Behrisch, R.; Garcia-Rosales, C.; Bekris, N.; Penzhorn, R.-D.

    2000-01-01

    Tritium depth profiling measurements by accelerator mass spectrometry have been performed at the facility installed at the Rossendorf 3 MV Tandetron. In order to achieve a uniform erosion at the target surface inside a commercial Cs ion sputtering source and to avoid edge effects, the samples were mechanically scanned and the signals were recorded only during sputtering at the centre of the sputtered area. The sputtered negative ions were mass analysed by the injection magnet of the Tandetron. Hydrogen and deuterium profiles were measured with the Faraday cup between the injection magnet and the accelerator, while the tritium was counted after the accelerator with semiconductor detectors. Depth profiles have been measured for carbon samples which had been exposed to the plasma at the first wall of the Garching fusion experiment ASDEX-Upgrade and from the European fusion experiment JET, Culham, UK

  3. Numerical Study of Single Bubble Growth on and Departure from a Horizontal Superheated Wall by Three-dimensional Lattice Boltzmann Method

    Science.gov (United States)

    Feng, Yuan; Li, Hui-Xiong; Guo, Kai-Kai; Zhao, Jian-Fu; Wang, Tai

    2018-05-01

    A three-dimensional hybrid lattice Boltzmann method was used to simulate the progress of a single bubble's growth and departure from a horizontal superheated wall. The evolutionary process of the bubble shapes and also the temperature fields during pool nucleate boiling were obtained and the influence of the gravitational acceleration on the bubble departure diameter (BDD), the bubble release frequency (BRF) and the heat flux on the superheated wall was analyzed. The simulation results obtained by the present three-dimensional numerical studies demonstrate that the BDD is proportional to g^{-0.301}, the BRF is proportional to g^{-0.58}, and the averaged wall heat flux is proportional to g^{0.201}, where g is the gravitational acceleration. These results are in good agreement with the common-used experimental correlations, indicating the rationality of the present numerical model and results.

  4. Dielectric constant of ionic solutions: a field-theory approach.

    Science.gov (United States)

    Levy, Amir; Andelman, David; Orland, Henri

    2012-06-01

    We study the variation of the dielectric response of a dielectric liquid (e.g. water) when a salt is added to the solution. Employing field-theoretical methods, we expand the Gibbs free energy to first order in a loop expansion and calculate self-consistently the dielectric constant. We predict analytically the dielectric decrement which depends on the ionic strength in a complex way. Furthermore, a qualitative description of the hydration shell is found and is characterized by a single length scale. Our prediction fits rather well a large range of concentrations for different salts using only one fit parameter related to the size of ions and dipoles.

  5. Suppression of electromechanical instability in fiber-reinforced dielectric elastomers

    Directory of Open Access Journals (Sweden)

    Rui Xiao

    2016-03-01

    Full Text Available The electromechanical instability of dielectric elastomers has been a major challenge for the application of this class of active materials. In this work, we demonstrate that dielectric elastomers filled with soft fiber can suppress the electromechanical instability and achieve large deformation. Specifically, we developed a constitutive model to describe the dielectric and mechanical behaviors of fiber-reinforced elastomers. The model was applied to study the influence of stiffness, nonlinearity properties and the distribution of fiber on the instability of dielectric membrane under an electric field. The results show that there exists an optimal fiber distribution condition to achieve the maximum deformation before failure.

  6. Hydrogen embrittlement corrosion failure of water wall tubes in large power station boilers

    International Nuclear Information System (INIS)

    Mathur, P.K.

    1981-01-01

    In the present paper, causes and mechanism of hydrogen embrittlement failure of water wall tubes in high pressure boilers have been discussed. A low pH boiler water environment, produced as a result of condenser leakage or some other type of system contamination and presence of internal metal oxide deposits, which permit boiler water solids to concentrate during the process of steam generation, have been ascribed to accelerate the formation of local corrosion cells conducive for acid attack resulting in hydrogen damage failure of water wall tubes. (author)

  7. Inverse design of dielectric materials by topology optimization

    DEFF Research Database (Denmark)

    Otomori, M.; Andkjær, Jacob Anders; Sigmund, Ole

    2012-01-01

    The capabilities and operation of electromagnetic devices can be dramatically enhanced if artificial materials that provide certain prescribed properties can be designed and fabricated. This paper presents a systematic methodology for the design of dielectric materials with prescribed electric...... permittivity. A gradient-based topology optimization method is used to find the distribution of dielectric material for the unit cell of a periodic microstructure composed of one or two dielectric materials. The optimization problem is formulated as a problem to minimize the square of the difference between...

  8. Effects of Moat Wall Impact on the Seismic Response of Base Isolated Nuclear Power Plants

    International Nuclear Information System (INIS)

    Kim, Min Kyu; Kim, Jung Han; Mosqueda, Gilberto; Sarebanhab, Alireza

    2015-01-01

    The objectives of this study are to examine the effects of impact on the response of seismically isolated NPPs and identify characteristics of the isolation hardware and hard stop that minimize these effects. Considering variable distances to the hard stop and properties of the moat wall, the amplification in response is reported for acceleration and floor spectral accelerations at different points along the height of a NPP containment structure. Base isolation can be an effective strategy to protect critical facilities such as Nuclear Power Plants (NPPs) from the damaging effects of horizontal earthquake ground shaking. To be effective in reducing accelerations and deformations of the structure above, the seismic isolation bearings can be subjected to large displacements. In the case of an extreme earthquake, bearing displacements need to be limited by a hard stop in order to prevent failure of the bearings. Impact to the hard stop, which is often the moat wall at the basement level, is also of significant concern due to the potential for increased transfer of forces and amplification in response of the structural system, piping and other contents. However, the consequences of impact or factors important to mitigate its effects are not very well understood. The main findings of this study are related to modeling of NPP with moat wall in OpenSees and LSDyna as well as observations resulting from the parametric study of the performance of the NPP under different intensity levels of seismic excitations for different properties of the moat wall and bearings. • Variation in the isolator properties should be considered when examining seismic pounding. For BDBE even, 58.5 % cases result to the impact for lower bound properties while this value was 5.5 % for upper bound properties. Since the impact results are dependent to the assumed bearing properties, a better range of properties can be obtained from experimental testing of the bearing under large shear strains.

  9. Vavilov-Cherenkov and transition radiations on the dielectric and metallic spheres

    International Nuclear Information System (INIS)

    Afanasiev, G.N.; Kartavenko, V.G.; Stepanovsky, Yu.P.

    2003-01-01

    Closed expressions are obtained for angular and frequency radiation intensities produced by a charge moving inside the dielectric sphere S, with observations made outside S (in fact, this is a typical experimental situation when a charge moves in one medium while measurements are made in the other one). It is shown that the difference in media properties inside and outside S drastically affects angular and frequency distributions. Also, a charge motion is considered which begins and terminates in medium 2 and which passes either through the dielectric sphere filled with medium 1 or through the metallic one. The energy flux in medium 2 involves the Vavilov-Cherenkov, transition radiation and the one arising from the charge instantaneous beginning and termination of motion. The evaluated angular and frequency distributions for various charge velocities and medium properties inside and outside S show that the standard identification of the charge velocity by its radiation on the part of the charge trajectory where βn>1 is not always valid. We analyze also the frequently used interpretation of the transition radiation in terms of instantaneous charge deceleration in one medium and its sudden acceleration in another one, and find them as to be insufficient. On the other hand, attempts to interpret the transition radiation in terms of semi-infinite motions terminating in one medium and beginning in the other one turn out to be correct if one takes into account the terms corresponding to the Vavilov-Cherenkov radiation

  10. Microwave measurement and modeling of the dielectric properties of vegetation

    Science.gov (United States)

    Shrestha, Bijay Lal

    Some of the important applications of microwaves in the industrial, scientific and medical sectors include processing and treatment of various materials, and determining their physical properties. The dielectric properties of the materials of interest are paramount irrespective of the applications, hence, a wide range of materials covering food products, building materials, ores and fuels, and biological materials have been investigated for their dielectric properties. However, very few studies have been conducted towards the measurement of dielectric properties of green vegetations, including commercially important plant crops such as alfalfa. Because of its high nutritional value, there is a huge demand for this plant and its processed products in national and international markets, and an investigation into the possibility of applying microwaves to improve both the net yield and quality of the crop can be beneficial. Therefore, a dielectric measurement system based upon the probe reflection technique has been set up to measure dielectric properties of green plants over a frequency range from 300 MHz to 18 GHz, moisture contents from 12%, wet basis to 79%, wet basis, and temperatures from -15°C to 30°C. Dielectric properties of chopped alfalfa were measured with this system over frequency range of 300 MHz to 18 GHz, moisture content from 11.5%, wet basis, to 73%, wet basis, and density over the range from 139 kg m-3 to 716 kg m-3 at 23°C. The system accuracy was found to be +/-6% and +/-10% in measuring the dielectric constant and loss factor respectively. Empirical, semi empirical and theoretical models that require only moisture content and operating frequency were determined to represent the dielectric properties of both leaves and stems of alfalfa at 22°C. The empirical models fitted the measured dielectric data extremely well. The root mean square error (RMSE) and the coefficient of determination (r2) for dielectric constant and loss factor of leaves

  11. Highly stretchable carbon nanotube transistors enabled by buckled ion gel gate dielectrics

    International Nuclear Information System (INIS)

    Wu, Meng-Yin; Chang, Tzu-Hsuan; Ma, Zhenqiang; Zhao, Juan; Xu, Feng; Jacobberger, Robert M.; Arnold, Michael S.

    2015-01-01

    Deformable field-effect transistors (FETs) are expected to facilitate new technologies like stretchable displays, conformal devices, and electronic skins. We previously demonstrated stretchable FETs based on buckled thin films of polyfluorene-wrapped semiconducting single-walled carbon nanotubes as the channel, buckled metal films as electrodes, and unbuckled flexible ion gel films as the dielectric. The FETs were stretchable up to 50% without appreciable degradation in performance before failure of the ion gel film. Here, we show that by buckling the ion gel, the integrity and performance of the nanotube FETs are extended to nearly 90% elongation, limited by the stretchability of the elastomer substrate. The FETs maintain an on/off ratio of >10 4 and a field-effect mobility of 5 cm 2 V −1 s −1 under elongation and demonstrate invariant performance over 1000 stretching cycles

  12. Plasmonic and Dielectric Metasurfaces: Design, Fabrication and Applications

    Directory of Open Access Journals (Sweden)

    Jian Wang

    2016-09-01

    Full Text Available Two-dimensional metasurfaces are widely focused on for their ability for flexible light manipulation (phase, amplitude, polarization over sub-wavelength propagation distances. Most of the metasurfaces can be divided into two categories by the material type of unit structure, i.e., plasmonic metasurfaces and dielectric metasurfaces. For plasmonic metasurfaces, they are made on the basis of metallic meta-atoms whose optical responses are driven by the plasmon resonances supported by metallic particles. For dielectric metasurfaces, the unit structure is constructed with high refractive index dielectric resonators, such as silicon, germanium or tellurium, which can support electric and magnetic dipole responses based on Mie resonances. The responses of plasmonic and dielectric metasurfaces are all relevant to the characteristics of unit structure, such as dimensions and materials. One can manipulate the electromagnetic field of light wave scattered by the metasurfaces through designing the dimension parameters of each unit structure in the metasurfaces. In this review article, we give a brief overview of our recent progress in plasmonic and dielectric metasurface-assisted nanophotonic devices and their design, fabrication and applications, including the metasurface-based broadband and the selective generation of orbital angular momentum (OAM carrying vector beams, N-fold OAM multicasting using a V-shaped antenna array, a metasurface on conventional optical fiber facet for linearly-polarized mode (LP11 generation, graphene split-ring metasurface-assisted terahertz coherent perfect absorption, OAM beam generation using a nanophotonic dielectric metasurface array, as well as Bessel beam generation and OAM multicasting using a dielectric metasurface array. It is believed that metasurface-based nanophotonic devices are one of the devices with the most potential applied in various fields, such as beam steering, spatial light modulator, nanoscale

  13. Dielectric behaviors of lead zirconate titanate ceramics with coplanar electrodes

    International Nuclear Information System (INIS)

    Wang, Y.; Cheng, Y.L.; Zhang, Y.W.; Chan, H.L.W.; Choy, C.L.

    2003-01-01

    This paper reports on the dielectric behaviors of lead zirconate titanate (PZT) capacitors with coplanar electrodes. Usually a ferroelectric device has a metal-ferroelectric-metal configuration (parallel plate capacitor); when both the electrodes are on one side of a ceramic to form a coplanar capacitor, different dielectric behaviors will be anticipated because of the change in the distribution of the test field inside the dielectrics. This paper describes how the capacitance and dielectric loss of PZT-based coplanar capacitors change with electrode distance, area and test frequency

  14. Synthesis and Characterization of High-Dielectric-Constant Nanographite-Polyurethane Composite

    Science.gov (United States)

    Mishra, Praveen; Bhat, Badekai Ramachandra; Bhattacharya, B.; Mehra, R. M.

    2018-05-01

    In the face of ever-growing demand for capacitors and energy storage devices, development of high-dielectric-constant materials is of paramount importance. Among various dielectric materials available, polymer dielectrics are preferred for their good processability. We report herein synthesis and characterization of nanographite-polyurethane composite with high dielectric constant. Nanographite showed good dispersibility in the polyurethane matrix. The thermosetting nature of polyurethane gives the composite the ability to withstand higher temperature without melting. The resultant composite was studied for its dielectric constant (ɛ) as a function of frequency. The composite exhibited logarithmic variation of ɛ from 3000 at 100 Hz to 225 at 60 kHz. The material also exhibited stable dissipation factor (tan δ) across the applied frequencies, suggesting its ability to resist current leakage.

  15. Electron-beam-induced conduction in dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Acris, F C; Davies, P M; Lewis, T J [University Coll. of North Wales, Bangor (UK). School of Electronic Engineering Science

    1976-03-14

    A model for the enhanced conduction induced in dielectric films under electron bombardment while electrically stressed is discussed. It is assumed that the beam produces a virtual electrode at the end of its range in the dielectric and, as a consequence, the induced conduction is shown to depend on the properties of that part of the dielectric beyond the range of the beam. This model has also been discussed recently by Nunes de Oliviera and Gross. In the present treatment, it is shown how the model permits investigation of beam scattering and carrier generation and recombination processes. Experiments on electron-bombardment-induced conduction of thin (72 to 360 nm) films of anodic tantalum oxide are reported and it is shown that the theoretical model provides a very satisfactory explanation of all features of the results including the apparent threshold energy for enhanced conduction.

  16. Studies on metal-dielectric plasmonic structures.

    Energy Technology Data Exchange (ETDEWEB)

    Chettiar, Uday K. (Purdue University, West Lafayette, IN); Liu, Zhengtong (Purdue University, West Lafayette, IN); Thoreson, Mark D. (Purdue University, West Lafayette, IN); Shalaev, Vladimir M. (Purdue University, West Lafayette, IN); Drachev, Vladimir P. (Purdue University, West Lafayette, IN); Pack, Michael Vern; Kildishev, Alexander V. (Purdue University, West Lafayette, IN); Nyga, Piotr (Purdue University, West Lafayette, IN)

    2010-01-01

    The interaction of light with nanostructured metal leads to a number of fascinating phenomena, including plasmon oscillations that can be harnessed for a variety of cutting-edge applications. Plasmon oscillation modes are the collective oscillation of free electrons in metals under incident light. Previously, surface plasmon modes have been used for communication, sensing, nonlinear optics and novel physics studies. In this report, we describe the scientific research completed on metal-dielectric plasmonic films accomplished during a multi-year Purdue Excellence in Science and Engineering Graduate Fellowship sponsored by Sandia National Laboratories. A variety of plasmonic structures, from random 2D metal-dielectric films to 3D composite metal-dielectric films, have been studied in this research for applications such as surface-enhanced Raman sensing, tunable superlenses with resolutions beyond the diffraction limit, enhanced molecular absorption, infrared obscurants, and other real-world applications.

  17. Extraction and dielectric properties of curcuminoid films grown on Si substrate for high-k dielectric applications

    Energy Technology Data Exchange (ETDEWEB)

    Dakhel, A.A.; Jasim, Khalil E. [Department of Physics, College of Science, University of Bahrain, P.O. Box 32038 (Bahrain); Cassidy, S. [Department of Basic Medical Sciences, Royal College of Surgeons in Ireland, Medical University of Bahrain, P.O. Box 15503 (Bahrain); Henari, F.Z., E-mail: fzhenari@rcsi-mub.com [Department of Basic Medical Sciences, Royal College of Surgeons in Ireland, Medical University of Bahrain, P.O. Box 15503 (Bahrain)

    2013-09-20

    Highlights: • The unknown insulating properties of curcuminoid extract are systematically studied. • Optical study gives a bandgap of 3.15 eV and a refractive index of 1.92 at 505 nm. • Turmeric is a high-k environmental friendly material for use in microelectronics. • Curcuminoid extract can be used as insulator of MIS devices with ε{sup ′}{sub ∞}≈54.2. -- Abstract: Curcuminoids were extracted from turmeric powder and evaporated in vacuum to prepare thin films on p-Si and glass substrates for dielectric and optical investigations. The optical absorption spectrum of the prepared amorphous film was not identical to that of the molecular one, which was identified by a strong wide absorption band in between ∼220 and 540 nm. The onset energy of the optical absorption of the film was calculated by using Hamberg et al. method. The dielectric properties of this material were systematically studied for future eco friendly applications in metal–insulator–semiconductor MIS field of applications. The complex dielectric properties were studied in the frequency range of 1–1000 kHz and was analysed in-terms of dielectric impedance Z{sup *}(ω) and modulus M{sup *}(ω). Generally, the curcuminoid complex can be considered as a high-k material and can be used in the environmental friendly production of microelectronic devices.

  18. Extraction and dielectric properties of curcuminoid films grown on Si substrate for high-k dielectric applications

    International Nuclear Information System (INIS)

    Dakhel, A.A.; Jasim, Khalil E.; Cassidy, S.; Henari, F.Z.

    2013-01-01

    Highlights: • The unknown insulating properties of curcuminoid extract are systematically studied. • Optical study gives a bandgap of 3.15 eV and a refractive index of 1.92 at 505 nm. • Turmeric is a high-k environmental friendly material for use in microelectronics. • Curcuminoid extract can be used as insulator of MIS devices with ε ′ ∞ ≈54.2. -- Abstract: Curcuminoids were extracted from turmeric powder and evaporated in vacuum to prepare thin films on p-Si and glass substrates for dielectric and optical investigations. The optical absorption spectrum of the prepared amorphous film was not identical to that of the molecular one, which was identified by a strong wide absorption band in between ∼220 and 540 nm. The onset energy of the optical absorption of the film was calculated by using Hamberg et al. method. The dielectric properties of this material were systematically studied for future eco friendly applications in metal–insulator–semiconductor MIS field of applications. The complex dielectric properties were studied in the frequency range of 1–1000 kHz and was analysed in-terms of dielectric impedance Z * (ω) and modulus M * (ω). Generally, the curcuminoid complex can be considered as a high-k material and can be used in the environmental friendly production of microelectronic devices

  19. On The Flow of Maxwell Fluid Between Two Walls Induced By A ...

    African Journals Online (AJOL)

    The flow of a Maxwell fluid between two side walls induced by a constant accelerating plate is revisited. In the present investigation, we employed asymptotic technique by assuming small and large relaxation times λ. We proved the uniqueness of our solution based on some simplifying assumption; the result shows that λ ...

  20. Analysis of terahertz dielectric properties of pork tissue

    Science.gov (United States)

    Huang, Yuqing; Xie, Qiaoling; Sun, Ping

    2017-10-01

    Seeing that about 70% component of fresh biological tissues is water, many scientists try to use water models to describe the dielectric properties of biological tissues. The classical water dielectric models are Debye model, Double Debye model and Cole-Cole model. This work aims to determine a suitable model by comparing three models above with experimental data. These models are applied to fresh pork tissue. By means of least square method, the parameters of different models are fitted with the experimental data. Comparing different models on both dielectric function, the Cole-Cole model is verified the best to describe the experiments of pork tissue. The correction factor α of the Cole-Cole model is an important modification for biological tissues. So Cole-Cole model is supposed to be a priority selection to describe the dielectric properties for biological tissues in the terahertz range.