WorldWideScience

Sample records for beam current drive

  1. Power threshold for neutral beam current drive

    International Nuclear Information System (INIS)

    For fully noninductive current drive in tokamaks using neutral beams, there is a power and density threshold condition, setting a minimum value for P3/2/n2. If this condition is not met, stationary state cannot occur, and a tokamak discharge will collapse. This is a consequence of the coupling between current and electron temperature, or between current drive efficiency and energy confinement time. 4 figs

  2. Neutral beam current drive scaling in DIII-D

    International Nuclear Information System (INIS)

    Neutral beam current drive scaling experiments have been carried out on the DIII-D tokamak at General Atomics. These experiments were performed using up to 10 MW of 80 keV hydrogen beams. Previous current drive experiments on DIII-D have demonstrated beam driven currents up to 340 kA. In the experiments reported here we achieved beam driven currents of at least 500 kA, and have obtained operation with record values of poloidal beta (εβ/sub p/ = 1.4). The beam driven current reported here is obtained from the total plasma current by subtracting an estimate of the residual Ohmic current determined from the measured loop voltage. In this report we discuss the scaling of the current drive efficiency with plasma conditions. Using hydrogen neutral beams, we find the current drive efficiency is similar in Deuterium and Helium target plasmas. Experiments have been performed with plasma electron temperatures up to T/sub e/ = 3 keV, and densities in the range 2 /times/ 1019m/sup /minus/3/ 19m/sup /minus/3/. The current drive efficiency (nIR/P) is observed to scale linearly with the energy confinement time on DIII-D to a maximum of 0.05 /times/ 1020m/sup /minus/2/ A/W. The measured efficiency is consistent with a 0-D theoretical model. In addition to comparison with this simple model, detailed analysis of several shots using the time dependent transport code ONETWO is discussed. This analysis indicates that bootstrap current contributes approximately 10--20% of the the total current. Our estimates of this effect are somewhat uncertain due to limited measurements of the radial profile of the density and temperatures. 4 refs., 1 fig., 1 tab

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

    Science.gov (United States)

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

    2007-11-01

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

  4. Intense relativistic electron beam injector system for tokamak current drive

    International Nuclear Information System (INIS)

    We report experimental and theoretical studies of an intense relativistic electron beam (REB) injection system designed for tokamak current drive experiments. The injection system uses a standard high-voltage pulsed REB generator and a magnetically insulated transmission line (MITL) to drive an REB-accelerating diode in plasma. A series of preliminary experiments has been carried out to test the system by injecting REBs into a test chamber with preformed plasma and applied magnetic field. REBs were accelerated from two types of diodes: a conventional vacuum diode with foil anode, and a plasma diode, i.e., an REB cathode immersed in the plasma. REB current was in the range of 50 to 100 kA and REB particle energy ranged from 0.1 to 1.0 MeV. MITL power density exceeded 10 GW/cm2. Performance of the injection system and REB transport properties is documented for plasma densities from 5 x 1012 to 2 x 1014 cm-3. Injection system data are compared with numerical calculations of the performance of the coupled system consisting of the generator, MITL, and diode

  5. Neutral Beam Heating and Current Drive in MAST

    Science.gov (United States)

    Akers, R.; Challis, C.; Appel, L.; Conway, N.; Cunningham, G.; Gryaznevich, M.; Lloyd, B.; Patel, A.; Tabasso, A.; Tournianski, M.

    2002-11-01

    Primary auxiliary heating on MAST (R 0.8m, a 0.6m) is provided by two ORNL neutral-beam injectors, oriented in the mid-plane, each with a tangency radius of 0.7m. Centrally peaked heating profiles at electron densities routinely exceeding the Greenwald limit are generated by injecting in the range 40 co-injection heated discharges and for low current (Ip 300kA), low-density (ne>0.5x1019m-3) co and counter injection heated plasmas where NBCD is being investigated.

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

    DEFF Research Database (Denmark)

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

    2015-01-01

    The neutral beam current drive efficiency has been investigated in the ASDEX Upgrade tokamak by replacing on-axis neutral beams with tangential off-axis beams. A clear modification of the radial fast-ion profiles is observed with a fast-ion D-alpha diagnostic that measures centrally peaked profil...

  7. Recent Improvements to the Control of the CTF3 High-Current Drive Beam

    CERN Document Server

    Constance, B; Gamba, D; Skowronski, P K

    2013-01-01

    In order to demonstrate the feasibility of the CLIC multiTeV linear collider option, the drive beam complex at the CLIC Test Facility (CTF3) at CERN is providing highcurrent electron pulses for a number of related experiments. By means of a system of electron pulse compression and bunch frequency multiplication, a fully loaded, 120 MeV linac is used to generate 140 ns electron pulses of around 28 Amperes. Subsequent deceleration of this high-current drive beam demonstrates principles behind the CLIC acceleration scheme, and produces 12 GHz RF power for experimental purposes. As the facility has progressed toward routine operation, a number of studies aimed at improving the drive beam performance have been carried out. Additional feedbacks, automated steering programs, and improved control of optics and dispersion have contributed to a more stable, reproducible drive beam with consequent benefits for the experiments.

  8. Neutral beam heating and current drive system and its role in ITER-FEAT operation scenarios

    International Nuclear Information System (INIS)

    The NB H and CD system, providing 33 MW in deuterium beams at 1 MeV from two injectors, in addition to 40 MW RF power, contributes to heating a plasma to sub-ignition through the L-H mode transition followed by finite-Q driven-burn (Q≥10), and achievement of a hybrid operation with an extended-duration (∼1000 s) or steady-state operation with Q≤5. To achieve such operations, the NB provides non-inductive current drive by injecting the beams tangentially into the plasma with the capability of on- and off-axis current drive. The present engineering design is under the constraints of the beam envelope, vacuum confinement, neutron shielding, tolerances, and clearances required with the toroidal field coils. The on- and off-axis current drive is to be achieved by tilting the beam axis vertically. Each beam axis of the NB injectors can be tilted independently, providing flexibility in the control of heating and the driven current profile. (author)

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

    International Nuclear Information System (INIS)

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

  10. Benchmarking of neutral beam current drive codes as a basis for the integrated modelling for ITER

    International Nuclear Information System (INIS)

    Neutral beam injection is a robust method for heating and current drive because it does not depend on any resonance conditions or coupling conditions at the edge. High-energy neutral beam current drive (NBCD) was experimentally validated for central current drive in JT-60U, giving a further confidence in ITER predictions. Recent progress in diagnostics, equilibrium solvers and analysis techniques enable rather detailed comparisons with NBCD codes. However, different codes give somewhat different results. Thus, we need to clarify physics implementations in NBCD codes, such as the beam model, ionization process, fast ion diffusion in the velocity space, orbit effects and electron shielding. Also from an integrated modelling viewpoint, an NBCD code benchmark is needed to establish a more solid basis for ITER operations. A benchmark of the Fokker-Planck code ACCOME has been performed against the orbit following Monte-Carlo code OFMC. Although calculated profiles agree rather well, the OFMC profile is slightly wider than the ACCOME one. The difference in the total fast ion current is ∼ 15%. We have examined fast ion diffusion in the 2D velocity space and observed difference in the diffusion in the pitch angle space. We have also examined orbit effects using a point source of the fast ions. Comparison of OFMC runs with and without the drift term in the orbit equation shows the finite banana width effect is not negligible. We have started a new NBCD code benchmark in the frame of the ITPA Steady-State Operation Topical Group with Fokker-Planck codes and orbit following Monte-Carlo codes such as OFMC, ACCOME, SPOT, NEMO, ASTRA, TRANSP/NUBEAM, ONETWO/NUBEAM, DRIFT and TOPICS. (author)

  11. CLIC Drive Beam Phase Stabilisation

    CERN Document Server

    Gerbershagen, Alexander; Schulte, Daniel

    The thesis presents phase stability studies for the Compact Linear Collider (CLIC) and focuses in particular on CLIC Drive Beam longitudinal phase stabilisation. This topic constitutes one of the main feasibility challenges for CLIC construction and is an essential component of the current CLIC stabilisation campaign. The studies are divided into two large interrelated sections: the simulation studies for the CLIC Drive Beam stability, and measurements, data analysis and simulations of the CLIC Test Facility (CTF3) Drive Beam phase errors. A dedicated software tool has been developed for a step-by-step analysis of the error propagation through the CLIC Drive Beam. It uses realistic RF potential and beam loading amplitude functions for the Drive and Main Beam accelerating structures, complete models of the recombination scheme and compressor chicane as well as of further CLIC Drive Beam modules. The tool has been tested extensively and its functionality has been verified. The phase error propagation at CLIC h...

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

    International Nuclear Information System (INIS)

    The negative ion based neutral beam (N-NB) current drive was experimentally studied. The N-NB driven current density was determined over a wide range of electron temperatures by using the motional Stark effect spectroscopy. Theoretical prediction of the NB current drive increasing with beam energy and electron temperature was validated. A record value of NB current drive efficiency 1.55 x 1019 Am-2W-1 was achieved simultaneously with high confinement and high beta at at a plasma current of 1.5 MA under a fully non-inductively current driven condition. The experimental validation of NB current drive theory for MHD quiescent plasmas gives greater confidence in predicting the NB current drive in future reactors. However, it was also found that MHD instabilities caused a degradation of NB current drive. A beam-driven instability expelled N-NB fast ions carrying non-inductive current from the central region. The lost N-NB driven current was estimated to be 7% of the total N-NB driven current. For the neoclassical tearing mode (NTM), comparisons of the measured neutron yield and fast ion pressure profile with transport code calculations revealed that the loss of fast ions increases with the NTM activity and that fast ions at higher energies suffer larger transport than at lower energies. (author)

  13. Noninductive current drive in tokamaks

    International Nuclear Information System (INIS)

    Various current drive mechanisms may be grouped into four classes: (1) injection of energetic particle beams; (2) launching of rf waves; (3) hybrid schemes, which are combinations of various rf schemes (rf plus beams, rf and/or beam plus ohmic heating, etc.); and (4) other schemes, some of which are specific to reactor plasma conditions requiring the presence of alpha particle or intense synchrotron radiation. Particle injection schemes include current drive by neutral beams and relativistic electron beams. The rf schemes include current drive by the lower hybrid (LH) waves, the electron waves, the waves in the ion cyclotron range of frequencies, etc. Only a few of these approaches, however, have been tested experimentally, with the broadest data base available for LH waves. Included in this report are (1) efficiency criteria for current drive, (2) current drive by neutral beam injection, (3) LH current drive, (4) electron cyclotron current drive, (5) current drive by ion cyclotron waves - minority species heating, and (6) current drive by other schemes (such as hybrids and low frequency waves)

  14. Fast wave current drive

    International Nuclear Information System (INIS)

    Experiments on the fast wave in the range of high ion cyclotron harmonics in the ACT-1 device show that current drive is possible with the fast wave just as it is for the lower hybrid wave, except that it is suitable for higher plasma densities. A 1400 loop antenna launched the high ion cyclotron harmonic fast wave [ω/Ω = O(10)] into a He+ plasma with n/sub e/approx. =4 x 1012 cm-3 and B = 4.5 kG. Probe and magnetic loop diagnostics and FIR laser scattering confirmed the presence of the fast wave, and the Rogowski loop indicated that the circulating plasma current increased by up to 40A with 1 kW of coupled power, which is comparable to lower hybrid current drive in the same device with the same unidirectional fast electron beam used as the target for the RF. A phased antenna array would be used for FWCD in a tokamak without the E-beam

  15. Design study of a new antenna system for steering microwave beam in electron cyclotron heating/current drive system

    International Nuclear Information System (INIS)

    The reflector driven in the linear motion to steer the microwave beam for electron cyclotron heating/current drive system, which has considerable merits, especially for reactor environments, has been studied in design. In a typical design, a microwave beam launched from the end of a waveguide is reflected at a concave mirror following a fixed flat mirror. The injection angle can be changed by varying a point of reflection on the concave mirror because of the transition of the normal angle of the concave mirror. The point of reflection is easily controlled by the linear motion of the concave mirror. It is notable that mirror rotation is not required, and the inside of a robust driving shaft can be used to supply the coolant to the mirror. This indicates that the antenna can be designed without a rotation axis, bearings, and a flexible cooling tube close to the plasma which may require frequent maintenance or replacement in a highly radioactive environment. This study shows that the antenna driven in the linear motion has a potential to meet certain specifications, especially with regard to antenna size, steerable range of the beam angle, and beam quality for experiments in tokamaks and for fusion reactors. In the preliminary design trial for the ITER equatorial antenna, the concaved mirror of 0.3 m in length having 1 m curvature and stroke of 0.2 m enables beam angle range of 20-40 deg. with beam radius of 0.06 m at the EC resonance

  16. Fast wave current drive

    Energy Technology Data Exchange (ETDEWEB)

    Goree, J.; Ono, M.; Colestock, P.; Horton, R.; McNeill, D.; Park, H.

    1985-07-01

    Fast wave current drive is demonstrated in the Princeton ACT-I toroidal device. The fast Alfven wave, in the range of high ion-cyclotron harmonics, produced 40 A of current from 1 kW of rf power coupled into the plasma by fast wave loop antenna. This wave excites a steady current by damping on the energetic tail of the electron distribution function in the same way as lower-hybrid current drive, except that fast wave current drive is appropriate for higher plasma densities.

  17. Turbulent current drive

    International Nuclear Information System (INIS)

    The Ohm's law is modified when turbulent processes are accounted for. Besides an hyper-resistivity, already well known, pinch terms appear in the electron momentum flux. Moreover it appears that turbulence is responsible for a source term in the Ohm's law, called here turbulent current drive. Two terms contribute to this source. The first term is a residual stress in the momentum flux, while the second contribution is an electro-motive force. A non zero average parallel wave number is needed to get a finite source term. Hence a symmetry breaking mechanism must be invoked, as for ion momentum transport. E × B shear flows and turbulence intensity gradients are shown to provide similar contributions. Moreover this source term has to compete with the collision friction term (resistivity). The effect is found to be significant for a large scale turbulence in spite of an unfavorable scaling with the ratio of the electron to ion mass. Turbulent current drive appears to be a weak effect in the plasma core, but could be substantial in the plasma edge where it may produce up to 10 % of the local current density

  18. CTF3 Drive Beam Injector Optimisation

    CERN Document Server

    AUTHOR|(CDS)2082899; Doebert, S

    2015-01-01

    In the Compact Linear Collider (CLIC) the RF power for the acceleration of the Main Beam is extracted from a high-current Drive Beam that runs parallel to the main linac. The main feasibility issues of the two-beam acceleration scheme are being demonstrated at CLIC Test Facility 3 (CTF3). The CTF3 Drive Beam injector consists of a thermionic gun followed by the bunching system and two accelerating structures all embedded in solenoidal magnetic field and a magnetic chicane. Three sub-harmonic bunchers (SHB), a prebuncher and a travelling wave buncher constitute the bunching system. The phase coding process done by the sub-harmonic bunching system produces unwanted satellite bunches between the successive main bunches. The beam dynamics of the CTF3 Drive Beam injector is reoptimised with the goal of improving the injector performance and in particular decreasing the satellite population, the beam loss in the magnetic chicane and the beam emittance in transverse plane compare to the original model based on P. Ur...

  19. Simulations for CLIC Drive Beam Linac

    CERN Document Server

    Aksoy, Avni

    2012-01-01

    The Drive Beam Linac of the Compact Linear Collider (CLIC) has to accelerate an electron beam with 4.2 A up to 2.4 GeV in almost fully-loaded structures. The pulse contains about 70000 bunches, one in every second rf bucket, and has a length of 140 $\\mu$s. The beam stability along the beamline is of concern for such a high current and pulse length. We present different options for the lattice of the linac based on FODO, triplet and doublet cells and compare the transverse instability for each lattice including the effects of beam jitter, alignment and beam-based correction. Additionally longitudinal stability is discussed for different bunch compressors using FODO type of lattice.

  20. Anomalous-viscosity current drive

    Science.gov (United States)

    Stix, T.H.; Ono, M.

    1986-04-25

    The present invention relates to a method and apparatus for maintaining a steady-state current for magnetically confining the plasma in a toroidal magnetic confinement device using anomalous viscosity current drive. A second aspect of this invention relates to an apparatus and method for the start-up of a magnetically confined toroidal plasma.

  1. Simulation of Phase Stability at the Flat Top of the CLIC Drive Beam

    CERN Document Server

    Gerbershagen, A; Burrows, P

    2011-01-01

    The drive beam phase stability is one of the critical issues of the Compact Linear Collider (CLIC). In this paper the generation and propagation of drive beam phase errors is studied for effects that vary during the drive beam pulse. This includes the influence of drive beam current and phase errors as well as of drive beam accelerator RF phase and amplitude errors on the drive beam phase after the compressor chicanes and the analysis of the propagation of these errors through the drive beam combination scheme. The impact of the imperfections on the main beam is studied including the possible correction with help of a feedforward system.

  2. Efficiency studies of high frequency current drive

    International Nuclear Information System (INIS)

    Pulsed high power free-electron-lasers (FELs) offer new possibilities for the current drive in tokamaks. High intensity FELs apply to the excitation of nonlinear wave-wave processes, such as beat-waves (BW) and stimulated Raman scattering (SRS), in which large phase velocity (vph>>ve) electrostatic modes are generated. These can accelerate resonant electrons to high parallel velocities v||∼vph, which produces a slowly decaying current. Furthermore, the fast electrons with v||>>v are not toroidally trapped into banana orbits. The operation at high frequencies provides for the FEL beam an easy access into the plasma centre. This makes possible to suppress sawtooth activity by profile control and to expand the operational limits in parameter space. Raman and beat-wave methods apply particularly well to bootstrap current seeding, which may considerably enhance the overall current drive efficiency. Both Raman forward (SRS-F) and backward (SRS-B) scattering can be applied to current drive. At high, reactor relevant temperatures SRS-F is the dominant process, because SRS-B is suppressed due to heavy damping of the plasma wave. At temperatures of a few keV, SRS-B dominates because of its short gain length. In this report we shall estimate the current drive efficiency at temperatures relevant for MTX and for a tokamak reactor. We shall also consider the dependence of the efficiency on the peak intensity of FEL in these two cases. (author) 8 refs., 2 figs., 1 tab

  3. CTF3 Drive Beam Accelerating Structures

    CERN Document Server

    Jensen, E

    2002-01-01

    The 3 GHz drive beam accelerator of the CLIC Test Facility CTF3, currently under construction at CERN, will be equipped with 16 novel SICA (Slotted Iris – Constant Aperture) accelerating structures. The slotted irises couple out the potentially disruptive induced transverse HOM energy to integrated silicon carbide loads (dipole mode Q's below 20). The use of nose cones for detuning allows a constant inner aperture (34 mm). The structures will be 1.2 m long and consist of 34 cells. A first 6 cell prototype structure has been tested successfully up to power levels of 100 MW (nominal: 30 MW), corresponding to surface electric field levels of 180 MV/m.

  4. Theoretical studies of non inductive current drive in compact toroids

    NARCIS (Netherlands)

    Farengo, R; Lifschitz, AF; Caputi, KI; Arista, NR; Clemente, RA

    2002-01-01

    Three non inductive current drive methods that can be applied to compact toroids axe studied. The use of neutral beams to drive current in field reversed configurations and spheromaks is studied using a Monte Carlo code that includes a complete ionization package and follows the exact particle orbit

  5. RF current drive components in a tokamak

    International Nuclear Information System (INIS)

    Theoretical analysis of low frequency current drive in a tokamak is presented. The global model discussed includes kinetic hot plasma effects and collisions. It is found that all kinds of wave-plasma interactions (resonant wave-electron interaction, resonant wave-ion interaction and collisions) can contribute to the current drive. The analysis presented stresses the two new current drive components, the resonant helicity current and the nonresonant collisionless current. Helicity current drive is proportional to the parallel helicity flux and to the wave damping strength, which is defined by the wave-plasma interaction process. The collisionless part of the nonresonant current is proportional to wave damping on ions. However, this is an electron current, and wave-ion interaction just creates necessary polarization of the wave to drive a current. The resistive MHD limit is considered as well, and the correct expression for the RF driven current including the Alfven resonance effect, is given. (author) 17 refs

  6. Design principles for high current beam injection lines

    International Nuclear Information System (INIS)

    We discuss the design principles for high current injection beam lines having a high degree of beam quality preservation. These principles are applied to designing a high current e-beam injection line delivering 10 MeV e-beams from the injector to an accelerator driving LTV FELs, as proposed at CEBAF

  7. Beam-driven and bootstrap currents in JT-60 upgrade

    International Nuclear Information System (INIS)

    We recently performed beam-driven current-drive experiments with a low fraction of bootstrap currents in a wide range of plasma parameters in JT-60 upgrade. The evidence of current profile modification by the beam-driven current with tangential neutral beam injectors. A high βN, high βp and ELMy H-mode plasma with possibly fully non-inductive current-drive by beam-driven and bootstrap currents was maintained for a considerably long duration with the combined injection of quasi-perpendicular and co-tangential beams. (author) 4 refs., 7 figs

  8. Beam dynamics design of the Compact Linear Collider Drive Beam injector

    International Nuclear Information System (INIS)

    In the Compact Linear Collider (CLIC) the RF power for the acceleration of the Main Beam is extracted from a high-current Drive Beam that runs parallel to the main linac. The longitudinal and transverse beam dynamics of the Drive Beam injector has been studied in detail and optimized. The injector consists of a thermionic gun followed by a bunching system, some accelerating structures, and a magnetic chicane. The bunching system contains three sub-harmonic bunchers, a prebuncher, and a traveling wave buncher all embedded in a solenoidal magnetic field. The main characteristic of the Drive Beam injector is the phase coding process done by the sub-harmonic bunching system operating at half the acceleration frequency. This process is essential for the frequency multiplication of the Drive Beam. During the phase coding process the unwanted satellite bunches are produced that adversely affects the machine power efficiency. The main challenge is to reduce the population of particles in the satellite bunches in the presence of strong space-charge forces due to the high beam current. The simulation of the beam dynamics has been carried out with PARMELA with the goal of optimizing the injector performance compared to the existing model studied for the Conceptual Design Report (CDR). The emphasis of the optimization was on decreasing the satellite population, the beam loss in the magnetic chicane and limiting the beam emittance growth in transverse plane

  9. Beam dynamics design of the Compact Linear Collider Drive Beam injector

    Energy Technology Data Exchange (ETDEWEB)

    Hajari, Sh. Sanaye, E-mail: ssanayeh@cern.ch [Institute for Research in Fundamental Sciences (IPM), School of Particles and Accelerators, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); European Organization for Nuclear Research (CERN), BE Department, CH-1211 Geneva 23 (Switzerland); Shaker, H. [Institute for Research in Fundamental Sciences (IPM), School of Particles and Accelerators, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); European Organization for Nuclear Research (CERN), BE Department, CH-1211 Geneva 23 (Switzerland); Doebert, S. [European Organization for Nuclear Research (CERN), BE Department, CH-1211 Geneva 23 (Switzerland)

    2015-11-01

    In the Compact Linear Collider (CLIC) the RF power for the acceleration of the Main Beam is extracted from a high-current Drive Beam that runs parallel to the main linac. The longitudinal and transverse beam dynamics of the Drive Beam injector has been studied in detail and optimized. The injector consists of a thermionic gun followed by a bunching system, some accelerating structures, and a magnetic chicane. The bunching system contains three sub-harmonic bunchers, a prebuncher, and a traveling wave buncher all embedded in a solenoidal magnetic field. The main characteristic of the Drive Beam injector is the phase coding process done by the sub-harmonic bunching system operating at half the acceleration frequency. This process is essential for the frequency multiplication of the Drive Beam. During the phase coding process the unwanted satellite bunches are produced that adversely affects the machine power efficiency. The main challenge is to reduce the population of particles in the satellite bunches in the presence of strong space-charge forces due to the high beam current. The simulation of the beam dynamics has been carried out with PARMELA with the goal of optimizing the injector performance compared to the existing model studied for the Conceptual Design Report (CDR). The emphasis of the optimization was on decreasing the satellite population, the beam loss in the magnetic chicane and limiting the beam emittance growth in transverse plane.

  10. CLIC Main Linac Beam-Loading Compensation by Drive Beam Phase Modulation

    CERN Document Server

    Corsini, R; Syratchev, I V

    1999-01-01

    The CLIC final focus momentum acceptance of ± 0.5 % limits the bunch-to-bunch energy variation in the main beam to less than ± 0.1 %, since the estimated single-bunch contribution is ± 0.4 %. On the other hand, a relatively high beam-loading of the main accelerating structures (about 16 %) is unavoidable in order to optimize the RF-to-beam efficiency. Therefore, a compensation method is needed to reduce the resulting bunch-to-bunch energy spread of the main beam. Up to now, it has been planned to obtain the RF pulse shape needed for compensation by means of a charge ramp in the drive beam pulse. On the other hand, the use of constant-current drive beam pulses would make the design and operation of the drive beam injector considerably simpler. In this paper we present a possible solution adapted to the CLIC two-beam scheme with constant-current pulses, based on phase modulation of the drive beam bunches.

  11. Lower hybrid current drive in tokamak plasmas

    International Nuclear Information System (INIS)

    Past ten years progress on Lower Hybrid Current Drive (LHCD) experiments have demonstrated the largest non-inductive current (3.6 MA, JT-60U), the longest current sustainment (2 hours, TRIAM-1M), non-inductive current drive at the highest density (n-bare - 1020m-3, ALCATOR-C) and the highest current drive efficiency (ηCD = 3.5x1019 m-2A/W, JT-60). These results indicate that LHCD is one of the most promising methods to drive non-inductive current in the present tokamak plasmas. This paper presents recent experimental results on LHCD experiments. Basic theories of LH waves, the wave propagation and the current drive are briefly summarized. The main part of this paper describes several important results and their physical pictures on recent LHCD experiments; 1) the experimental set-up, 2) the current drive efficiency, 3) the control of current profile and MHD activities, 4) the global energy confinement, 5) the global power flow, 6) fast electron behavior, 7) interaction between LH waves and thermal/fast ions, 8) combination with other CD method. (author)

  12. Stabilization of tearing mode by current drive

    Institute of Scientific and Technical Information of China (English)

    WANG Zhong-tian; SHI Man-li; MAO Guo-ping; ZHAO Shan-zhong; ZHENG Xiao-hu

    2004-01-01

    The major disruption limits the operation of present tokamaks. Experimental evidences point out that the growth of tearing modes or the magnetic islands is primarily responsible for the occurrence. Taking the non-inductive current drive effects into account, a set of 3D nonlinear equation is derived. It is shown from simulation that the growth of the magnetic island is suppressed effectively by RF current drive. It is consistent with recent experiments on the HL-1 tokamak in which the plasma is stabilized by an RF current drive.

  13. Combined RF current drive and bootstrap current in tokamaks

    International Nuclear Information System (INIS)

    By calculating radio frequency current drive (RFCD) and the bootstrap current in a consistent kinetic manner, we find synergistic effects in the total noninductive current density in tokamaks [1]. We include quasilinear diffusion in the Drift Kinetic Equation (DKE) in order to generalize neoclassical theory to highly non-Maxwellian electron distributions due to RFCD. The parallel plasma current is evaluated numerically with the help of the FASTEP Fokker-Planck code [2]. Current drive efficiency is found to be significantly affected by neoclassical effects, even in cases where only circulating electrons interact with the waves. Predictions of the current drive efficiency are made for lower hybrid and electron cyclotron wave current drive scenarios in the presence of bootstrap current. (c) 1999 American Institute of Physics

  14. Passive cyclotron current drive for fusion plasmas

    International Nuclear Information System (INIS)

    The creation of toroidal current using cyclotron radiation in a passive way is, together with the well known bootstrap current, an interesting method for stationary current drive in high-temperature fusion reactors. Here, instead of externally applied RF-waves, fish-scale like structures at the first wall help to create enough asymmetry in the self generated cyclotron radiation intensity to drive a current within the plasma. The problem of computing passive cyclotron current drive consists of actually two linked problems, which are the computation of the electron equilibrium under the presence of self-generated radiation, and the computation of the photon equilibrium in a bounded system with a distorted electron distribution. This system of integro-differential equations cannot be solved directly in an efficient way. Therefore a linearization procedure was developed to decouple both sets of equations, finally linked through a generalized local current drive efficiency. The problem of the exact accounting for the wall profile effects was reduced to the solution of a Fredholm-type integral equation of the 2nd-kind. Based on all this an extensive computer code was developed to compute the passively driven current as well as radiation losses, radiation transport and overall efficiencies. The results therefrom give an interesting and very detailed insight into the problems related to passive cyclotron current drive

  15. ECRH current drive in tokamak plasmas

    International Nuclear Information System (INIS)

    The current drive by electron cyclotron resonance heating (ECRH) is investigated in a typical magnetic field of tokamak with circular cross section. The trapped electrons and the modification of electron-cyclotron resonance condition by the relativistic mass increase are shown to have significant effects on the efficiency of this current drive. The efficiency strongly depends on the values of the parallel velocity u0 of resonant electrons, the inverse aspect ratio ε, the poloidal angle θ0 of absorption point, and the relativistic parameter S, which represents the strength of the relativistic correction to the resonance condition. (author)

  16. LEDA beam diagnostics instrumentation: Beam current measurement

    International Nuclear Information System (INIS)

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

  17. Nondestructive synchronous beam current monitor

    International Nuclear Information System (INIS)

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

  18. Theory of current-drive in plasmas

    International Nuclear Information System (INIS)

    The continuous operation of a tokamak fusion reactor requires, among other things, a means of providing continuous toroidal current. Such operation is preferred to the conventional pulsed operation, where the plasma current is induced by a time-varying magnetic field. A variety of methods has been proposed to provide continuous current, including methods which utilize particle beams or radio frequency waves in any of several frequency regimes. Currents as large as half a mega-amp have now been produced in the laboratory by such means, and experimentation in these techniques has now involved major tokamak facilities worldwide

  19. Digitally compensated beam current transformer

    CERN Document Server

    Kesselman, Martin

    2005-01-01

    The Spallation Neutron Source (SNS) is being built by a collaboration of six laboratories. Beam current monitors (BCMs) will be used to record the current of H-minus and H-plus beams ranging from 15 mA (tune-up in the Front End and Linac) to over 60A fully accumulated in the Ring and dumped to the load as a single pulse in the Ring to Beam Target (RTBT). The time structure of these beams ranges from 645ns "mini" bunches at the 1.05 MHz ring revolution rate, to an overall 1 ms long macro-pulse. The requirements for the BCMs will depend upon their location within the system. The need to measure individual mini-pulses, examine the characteristics of the chopper edge, as well as the longer average current pulse of the macropulse, or long duration pulses during Linac tuning place wide requirements upon the response of current transformers. To obtain the desired accuracy and resolution, current transformers must have less than 1 ns rise time and droops of 0.1 %/ms. This places a significant design burden on the cur...

  20. Review of the experimental papers at the IAEA conference on noninductive current drive, Culham, 1983

    International Nuclear Information System (INIS)

    Three types of noninductive current drive experiments have been reported at this conference: (1) neutral beam (2) rf current drive, and (3) relativistic electron beams (REB). If we compare the effort to develop current drive to a horse race, the neutral beam horse was first out of the gates, but it quickly found greener pastures (heating) and has dropped temporarily out of the race. The lower hybrid horse now has a big lead at the first furlong (200 m), but the bulk of the race remains to be run. The fast wave and REB horses have yet to get up speed

  1. Review of the experimental papers at the IAEA conference on noninductive current drive, Culham, 1983

    Energy Technology Data Exchange (ETDEWEB)

    Motley, R.W.

    1983-10-01

    Three types of noninductive current drive experiments have been reported at this conference: (1) neutral beam (2) rf current drive, and (3) relativistic electron beams (REB). If we compare the effort to develop current drive to a horse race, the neutral beam horse was first out of the gates, but it quickly found greener pastures (heating) and has dropped temporarily out of the race. The lower hybrid horse now has a big lead at the first furlong (200 m), but the bulk of the race remains to be run. The fast wave and REB horses have yet to get up speed.

  2. Current Sensor Fault Reconstruction for PMSM Drives.

    Science.gov (United States)

    Huang, Gang; Luo, Yi-Ping; Zhang, Chang-Fan; He, Jing; Huang, Yi-Shan

    2016-01-01

    This paper deals with a current sensor fault reconstruction algorithm for the torque closed-loop drive system of an interior PMSM. First, sensor faults are equated to actuator ones by a new introduced state variable. Then, in αβ coordinates, based on the motor model with active flux linkage, a current observer is constructed with a specific sliding mode equivalent control methodology to eliminate the effects of unknown disturbances, and the phase current sensor faults are reconstructed by means of an adaptive method. Finally, an αβ axis current fault processing module is designed based on the reconstructed value. The feasibility and effectiveness of the proposed method are verified by simulation and experimental tests on the RT-LAB platform. PMID:26840317

  3. Current Sensor Fault Reconstruction for PMSM Drives

    Directory of Open Access Journals (Sweden)

    Gang Huang

    2016-01-01

    Full Text Available This paper deals with a current sensor fault reconstruction algorithm for the torque closed-loop drive system of an interior PMSM. First, sensor faults are equated to actuator ones by a new introduced state variable. Then, in αβ coordinates, based on the motor model with active flux linkage, a current observer is constructed with a specific sliding mode equivalent control methodology to eliminate the effects of unknown disturbances, and the phase current sensor faults are reconstructed by means of an adaptive method. Finally, an αβ axis current fault processing module is designed based on the reconstructed value. The feasibility and effectiveness of the proposed method are verified by simulation and experimental tests on the RT-LAB platform.

  4. Current drive by intense microwave pulses

    International Nuclear Information System (INIS)

    The advent of high-peak-power pulsed microwave sources opens possibilities for novel current-drive schemes in tokamaks. Four such schemes are considered: accelerating phase-space buckets, overlap of relativistic electron-cyclotron harmonics, beat-wave generation and burnthrough of intense lower-hybrid waves. These schemes are found to offer one or more of the following advantages over their continuous-power counterparts: improved efficiency, improved access to the core plasma, and precise control of the deposition profile. 17 refs

  5. Constant current electric motor drive for fan

    Energy Technology Data Exchange (ETDEWEB)

    Church, C.A.

    1988-03-23

    A motor for driving air through a replaceable filter to the face of a wearer of a protective helmet is supplied with power from a rechargeable battery pack through a current regulator which is controlled to tend to maintain the motor current constant in spite of variations in the battery voltage or the degree of clogging of the filter. The voltage across the motor, measured by resistors can be used as a measure of the degree of clogging of the filter to actuate an audible or visible alarm if the filter becomes too clogged. The voltage across the regulator measured by resistors can be used as a measure of the voltage of the battery to give a visible or audible warning if the battery charge gets too low. The two different warnings can be distinguishable from one another.

  6. Study of EC current drive efficiency and bootstrap current by power modulation experiments

    International Nuclear Information System (INIS)

    In Stellarators, the absence of a strong 'obscuring' Ohmic component permits the experimental investigation of small non-inductive currents with a precision difficult to be obtained in an equivalent Tokamak. In the W7-AS Stellarator (R = 2 m, ≤0.18 m, PECRH ≤ 800 kW) we have performed a systematic study of Electron Cyclotron Current Drive. Uncertainties in the measurements of the ECCD efficiency, ηECCD, are introduced by the unavoidable presence of the bootstrap current (and, eventually, an Ohmic one) and by the strong coupling between confinement properties and rotational transform, which is typical for low-shear vacuum magnetic field configurations, as W7-AS. To improve the accuracy, we have applied a new perturbative procedure for the determination of ηECCD. The method is based on the independent launch of two microwave beams. While one of the two beams is launched with a toroidal angle of injection corresponding to co-current drive (with respect to the bootstrap current direction) the second one is injected in the opposite direction (counter-current drive). In absence of effects perturbing the symmetry (e.g., strong E|| as in Tokamaks, or strong anisotropic electron distribution functions as in presence of LHCD) the two r.f. beams are equivalently absorbed and the two driven currents compensate. Through a modulation of the powers in both beam with same amplitude but opposite phase, the modulated ECCD contribution can be discriminated from the unaffected bootstrap and Ohmic ones. Furthermore, the time delay between the modulated power and the response of the loop voltage contains information about the radial localization of the modulated ECCD-current. (author) 6 refs., 5 figs

  7. Beam current measurement and beam positioning for baby-ebm

    International Nuclear Information System (INIS)

    This paper describes the electron beam detection of Baby EBM. The detection is divided by two categories; beam current measurement and beam positioning under the scanning window. The beam detector system was completely fabricated and tested and the detector was able to detect the electron beam of Baby EBM. It has been found that the beam current of this EBM is 1.62 mA for energy of 0.14 MeV. A higher beam current can be obtained if a proper cooling system to the window foil is installed. (Author)

  8. Assessment of Electron-Cyclotron-Current-Drive-Assisted Operation in DEMO

    Directory of Open Access Journals (Sweden)

    Marushchenko N.B.

    2012-09-01

    Full Text Available The achievable efficiency for external current drive through electron-cyclotron (EC waves in a demonstration tokamak reactor is discussed. Two possible reactor designs, one for steady state and one for pulsed operation, are considered. It is found that for midplane injection the achievable current drive efficiency is limited by secondharmonic absorption at levels consistent with previous studies. Propagation through the second-harmonic region can be reduced by moving the launch position to the high-field side (this can be obtained by injecting the beam from an upper port in the vacuum vessel. In this case, beam tracing calculations deliver values for the EC current drive efficiency approaching those usually reported for neutral beam current drive.

  9. Plasma current profile shaping with rf-current drive

    Energy Technology Data Exchange (ETDEWEB)

    Ehst, D.A.; Evans, K. Jr.

    1985-01-01

    Calculations of rf current drive in a toroidal geometry are presented. The result is self-consistent in that the tokamak magnetic field generated by the rf-driven current is used to compute the wave trajectory and spatial damping in the plasma. In the next section we derive the quasilinear theory in an axisymmetric torus. In Section 3 we describe a numerical solution to this problem and investigate rf-generated equilibria in a reactor-relevant geometry (A = 6.0; major radius, R/sub 0/ = 5.25 m; elongation k = 1.6; triangular boundary). By suitably adjusting the rf/plasma parameters a wide range of equilibria can be created. Although we have not optimized our rf-generated equilibria (in particular, we are limited at present to a narrow spectrum) we find evidence that equilibria can be sustained which should lead to attractive tokamak reactors.

  10. Fabrication of Beam-rotating Actuator for Multiple-beam Disk Drive

    Science.gov (United States)

    Kim, Boung Jun; Kim, Soo Hyun; Kwak, Yoon Keun

    2002-05-01

    Current trends in computer and communication industries are towards increasingly higher resolution images and video processing techniques. However, such sophisticated processing tasks require massive storage systems such as a compact disk read only memory (CD-ROM) and digital versatile disc (DVD). Current demands in the development of such systems are higher data density storage media and an improved data transfer rate. The latter is discussed in this paper. A multiple-beam optical disk drive is presented as a method for improving the effective data transfer rate by increasing the beam spot number formed on an optical disk. The beam-rotating actuator is necessary for positioning the multiple-beam onto more than one track. Ray tracing was also employed for the real system setup. The beam-rotating actuator is made up of piezoelectric material, a high-stiffness wire hinge and a dove prism. The actuator has an approximately 1 kHz resonance frequency and a suitable operational range. The dynamic equation for the actuator is derived for the control of the real system.

  11. Current drive, heating and fueling by compact torus injection

    International Nuclear Information System (INIS)

    The possibility of injecting small compact-torus (CT) plasma rings into magnetic fusion devices is considered. This discussion concentrates on a proposed new method for efficient current drive in Tokamaks and other toroidal devices in which the magnetic flux in the CT acts to excite the current. In addition to this aspect, CTs may be selectively loaded with matter or energetic particles, or may be accelerated to high kinetic energy (0.1 to 1 MeV/ion) to provide fuel or auxiliary heating for low-density fusion devices including tandem mirrors. The potential exists for high-Q (approx. 100) Tokamak operation as well as penetration to distances well beyond those available by neutral beams or fuel particles

  12. Current drive by electron cyclotron waves in stellarators

    International Nuclear Information System (INIS)

    In this paper we propose a method to estimate the induced current by Electron Cyclotron waves fast enough, from the numerical point of view, to be included in a ray-tracing code, and yet accounting for the complicated geometry of stellarators. Since trapped particle effects are particularly important in this Current Drive method and in stellarator magnetic configuration, they are considered by the modification they introduce in the current drive efficiency. Basically, the method consists of integrating the Fisch and Boozer relativistic efficiency, corrected with the effect of trapped particles, times the absorbed power per momentum interval. This one is calculated for a Maxwellian distribution function, assuming a nearly linear regime. The influence of impurities and of species which are not protons is studied, calculating the efficiency for plasmas with Zeff) - Finally, a numerical analysis particularized to TJ-II stellarator is presented. The absorbed power density is calculated by the ray tracing code RAYS, taking into account the actual microwave beam structure. (Author) 23 refs

  13. Global analysis of radio-frequency current drive

    International Nuclear Information System (INIS)

    A theoretical analysis of radio-frequency current drive in a tokamak at frequencies much less than the electron cyclotron frequency is presented. The global model discussed includes kinetic hot plasma effects and collisions. It is found that all kinds of wave plasma interactions (resonant wave-electron interaction, resonant wave-ion interaction and collisions) can contribute to the current drive. The analysis presented discusses the following important current drive components: the momentum-transfer current and polarization current, the helicity current, the resonant and non resonant currents, the currents caused by kinetic and collisional effects. Expressions for all current drive components are derived, and comparison with the results on helicity current drive obtained by other researchers is given. (author)

  14. A survey of the current experimental database for lower hybrid current-drive and heating

    International Nuclear Information System (INIS)

    The proposed ITER design may rely heavily on Lower Hybrid waves to provide heating, current drive, MHD stabilization through current profile modification and transformer recharging. This paper presents a detailed survey of recent LH experimental results from PLT, Alcator C, ASDEX, Petula-B, FT and JT-60. Current drive and heating efficiencies are given, as well as regimes where sawteeth and m = 1 and 2 oscillations are stabilized. In addition, in ASDEX and JT-60, LH waves in combination with neutral beams, (a possible ITER scenario) experiments are examined. Finally, the current drive efficiency for ITER is obtained by extrapolating from the LHCD database. Assuming 12 MW of LH power, approximately 4.5 to 5.6 MA of current could be driven in ITER. However, the high density (/ovr /n///sub e/ = 8 /times/ 1019 m/sup /minus/3/) and high temperature (/ovr/T///sub e/ = 21 keV) will preclude wave penetration to the center. Assuming a narrow N/sub /parallel// spectrum (1.2 /approx lt/ N/sub /parallel// /approx lt/ 2) the LH waves should be absorbed within the outer half of the plasma. 43 refs., 18 figs., 10 tabs

  15. Current drive and sustain experiments with the bootstrap current in JT-60

    International Nuclear Information System (INIS)

    The current drive and sustain experiments with the neoclassical bootstrap current are performed in the JT-60 tokamak. It is shown that up to 80% of total plasma current is driven by the bootstrap current in extremely high βp regime (βp = 3.2) and the current drive product Ip (bootstrap) n-bareRp up to 4.4 x 1019 MAm-2 has been attained with the bootstrap current. The experimental resistive loop voltages are compared with the calculations using the neoclassical resistivity with and without the bootstrap current and the Spitzer resistivity for a wide range of the plasma current (Ip = 0.5 -2 MA) and the poloidal beta (βp = 0.1 - 3.2). The calculated resistive loop voltage is consistent with the neoclassical prediction including the bootstrap current. Current sustain with the bootstrap current is tested by terminating the Ip feedback control during the high power neutral beam heating. An enhancement of the L/R decay time than those expected from the plasma resistivity with measured Te and Zeff has been confirmed experimentally supporting the large non-inductive current in the plasma and is consistent with the neoclassical prediction. A new technique to calculate the bootstrap current in multi-collisionality regime for finite aspect ratio tokamak has bee developed. The neoclassical bootstrap current is calculated directly through the force balance equations between viscous and friction forces according to the Hirshman-Sigmar theory. The bootstrap current driven by the fast ion component is also included. Ballooning stability of the high βp plasma are analyzed using the current profiles including the bootstrap current. The plasma pressure is close to the ballooning limit in high βp discharges. (author)

  16. High current beam transport with multiple beam arrays

    International Nuclear Information System (INIS)

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

  17. Power and momentum relations in rotating magnetic field current drive

    International Nuclear Information System (INIS)

    The use of rotating magnetic fields (RMF) to drive steady currents in plasmas involves a transfer of energy and angular momentum from the radio frequency source feeding the rotating field coils to the plasma. The power-torque relationships in RMF systems are discussed and the analogy between RMF current drive and the polyphase induction motor is explained. The general relationship between the energy and angular momentum transfer is utilized to calculate the efficiency of the RMF plasma current drive. It is found that relatively high efficiencies can be achieved in RMF current drive because of the low phase velocity and small slip between the rotating field and the electron fluid

  18. The role of heating and current drive in ITER

    International Nuclear Information System (INIS)

    This report discusses and summarize the role of heating and non-inductive current drive in ITER as: (1) ITER must have heating power sufficient for ignition. (2) The heating system must be capable of current drive. (3) Steady-state operation is an ''ultimate goal.'' It is recognized that additional heating and current drive power (beyond what is initially installed on ITER) may be required. (4) The ''Ultimate goal of steady-state operation'' means steady-state with QCD ≥ 5. Unlike the ''Terms of Reference'' for the ITER CDA, the ''ITER Technical Objectives and Approaches'' for the EDA sets no goal for the neutron wall load during steady-state operation. (5) In addition to bulk current drive, the ITER heating and current drive system should be used for current profile control and for burn control

  19. Laser diagnostic for high current H- beams

    International Nuclear Information System (INIS)

    In the last 5 years, significant technology advances have been made in the performance, size, and cost of solid-state diode-pumped lasers. These developments enable the use of compact Q-switched Nd:YAG lasers as a beam diagnostic for high current H- beams. Because the threshold for photodetachment is only 0.75 eV, and the maximum detachment cross section is 4x10-17cm2 at 1.5 eV, A 50 mJ/pulse Q-switched Nd:YAG laser can neutralize a significant fraction of the beam in a single 10 ns wide pulse. The neutral beam maintains nearly identical parameters as the parent H- beam, including size, divergence, energy, energy spread, and phase spread. A dipole magnet can separate the neutral beam from the H- beam to allow diagnostics on the neutral beam without intercepting the high-current H- beam. Such a laser system can also be used to extract a low current proton beam, or to induce fluorescence in partially stripped heavy ion beams. Possible beamline diagnostic systems will be reviewed, and the neutral beam yields will be calculated. copyright 1998 American Institute of Physics

  20. Numerical simulations of driving beam dynamics in the plasma wakefield accelerator

    International Nuclear Information System (INIS)

    Novel plasma based acceleration devices have become the subject of active research because of their ability to support acceleration gradients in excess of 10 GeV/m. The plasma wakefield accelerator (PWFA) is one such device which consists of an intense electron beam (the primary beam) whose purpose is to excite a plasma wave which, in turn, accelerates a trailing electron bunch (the secondary beam). Two issues of current interest in the PWFA are (1) the equilibrium and stability of the driving beam and (2) the effect of the wakefield on the quality of the trailing electron bunch. In the UCLA experiment, a question of particular interest is the equilibrium state of the driving electron beam. Two intriguing suggestions have been made. The first is that in the limit that the beam density greatly exceeds the plasma density, the plasma electrons will be completely expelled from the axis. The second is that, in parameter regimes of interest, the driving beam will experience a severe radial pinching force. In order to investigate these assertions, the authors first consider the envelope equation for an electron beam propagating in a plasma with nb ≥ np. They then compare numerical solutions of this equation to results obtained via two-dimensional axisymmetric (r,z) particle simulation using the GRIEZR particle simulation code

  1. Plasma Heating and Current Drive for Fusion Reactors

    Science.gov (United States)

    Holtkamp, Norbert

    2010-02-01

    ITER (in Latin ``the way'') is designed to demonstrate the scientific and technological feasibility of fusion energy. Fusion is the process by which two light atomic nuclei combine to form a heavier one and thus release energy. In the fusion process two isotopes of hydrogen - deuterium and tritium - fuse together to form a helium atom and a neutron. Thus fusion could provide large scale energy production without greenhouse effects; essentially limitless fuel would be available all over the world. The principal goals of ITER are to generate 500 megawatts of fusion power for periods of 300 to 500 seconds with a fusion power multiplication factor, Q, of at least 10. Q >= 10 (input power 50 MW / output power 500 MW). In a Tokamak the definition of the functionalities and requirements for the Plasma Heating and Current Drive are relevant in the determination of the overall plant efficiency, the operation cost of the plant and the plant availability. This paper summarise these functionalities and requirements in perspective of the systems under construction in ITER. It discusses the further steps necessary to meet those requirements. Approximately one half of the total heating will be provided by two Neutral Beam injection systems at with energy of 1 MeV and a beam power of 16 MW into the plasma. For ITER specific test facility is being build in order to develop and test the Neutral Beam injectors. Remote handling maintenance scheme for the NB systems, critical during the nuclear phase of the project, will be developed. In addition the paper will give an overview over the general status of ITER. )

  2. Crossed-beam energy transfer in direct-drive implosions

    Energy Technology Data Exchange (ETDEWEB)

    Seka, W; Edgell, D H; Michel, D T; Froula, D H; Goncharov, V N; Craxton, R S; Divol, L; Epstein, R; Follett, R; Kelly, J H; Kosc, T Z; Maximov, A V; McCrory, R L; Meyerhofer, D D; Michel, P; Myatt, J F; Sangster, T C; Shvydky, A; Skupsky, S

    2012-05-22

    Direct-drive-implosion experiments on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] have showed discrepancies between simulations of the scattered (non-absorbed) light levels and measured ones that indicate the presence of a mechanism that reduces laser coupling efficiency by 10%-20%. This appears to be due to crossed-beam energy transfer (CBET) that involves electromagnetic-seeded, low-gain stimulated Brillouin scattering. CBET scatters energy from the central portion of the incoming light beam to outgoing light, reducing the laser absorption and hydrodynamic efficiency of implosions. One-dimensional hydrodynamic simulations including CBET show good agreement with all observables in implosion experiments on OMEGA. Three strategies to mitigate CBET and improve laser coupling are considered: the use of narrow beams, multicolor lasers, and higher-Z ablators. Experiments on OMEGA using narrow beams have demonstrated improvements in implosion performance.

  3. Sensorless optimal sinusoidal brushless direct current for hard disk drives

    Science.gov (United States)

    Soh, C. S.; Bi, C.

    2009-04-01

    Initiated by the availability of digital signal processors and emergence of new applications, market demands for permanent magnet synchronous motors have been surging. As its back-emf is sinusoidal, the drive current should also be sinusoidal for reducing the torque ripple. However, in applications like hard disk drives, brushless direct current (BLDC) drive is adopted instead of sinusoidal drive for simplification. The adoption, however, comes at the expense of increased harmonics, losses, torque pulsations, and acoustics. In this paper, we propose a sensorless optimal sinusoidal BLDC drive. First and foremost, the derivation for an optimal sinusoidal drive is presented, and a power angle control scheme is proposed to achieve an optimal sinusoidal BLDC. The scheme maintains linear relationship between the motor speed and drive voltage. In an attempt to execute the sensorless drive, an innovative power angle measurement scheme is devised, which takes advantage of the freewheeling diodes and measures the power angle through the detection of diode voltage drops. The objectives as laid out will be presented and discussed in this paper, supported by derivations, simulations, and experimental results. The proposed scheme is straightforward, brings about the benefits of sensorless sinusoidal drive, negates the need for current sensors by utilizing the freewheeling diodes, and does not incur additional cost.

  4. RF helicity injection and current drive

    International Nuclear Information System (INIS)

    The relation between RF-driven current and wave helicity is analytically and numerically studied for a tokamak plasma. The helicity conversion coefficient from the wave to the plasma is generally obtained and numerically examined for the waves in the range of ion cyclotron frequency. The wave propagation equation which includes kinetic effects is solved as a boundary-value problem with one-dimensional inhomogeneities. It is shown that the wave helicity well satisfies the continuity equation. We confirm that the RF-helicity injection is not an identical phenomenon of the reduction of the one turn loop voltage due to the RF-driven current. (author)

  5. A Study of the Beam Physics in the CLIC Drive Beam Decelerator

    CERN Document Server

    Adli, Erik; Stapnes, Steinar

    2009-01-01

    CLIC is a study for a Multi-TeV e+e- linear collider, in which the rf power for the main linacs is extracted from 100 ampere electron drive beams, by the use of specially designed power extraction structures. Up to 90% of the beam energy is extracted from the drive beams along one kilometer long decelerator sectors, rendering the beam transport challenging. We have identified two major challenges for robust beam transport: the significant transverse wakes in the power extraction structures, and the large energy spread induced by the power extraction process. By beam dynamics studies we have qualified power extraction structure designs, leading to the present CLIC baseline structure in which the transverse wakes are sufficiently mitigated. We have further shown that the beam energy spread induced by the deceleration implies that standard 1-to-1 correction might not ensure satisfactory drive beam transport. As alternative, we propose a decelerator orbit correction scheme based on dispersion-free steering and ex...

  6. Plasma heating and current drive using intense, pulsed microwaves

    International Nuclear Information System (INIS)

    The use of powerful new microwave sources, e.g., free-electron lasers and relativistic gyrotrons, provide unique opportunities for novel heating and current-drive schemes in the electron-cyclotron and lower-hybrid ranges of frequencies. These high-power, pulsed sources have a number of technical advantages over conventional, low-intensity sources; and their use can lead to improved current-drive efficiencies and better penetration into a reactor-grade plasma in specific cases. The Microwave Tokamak Experiment at Lawrence Livermore National Laboratory will provide a test for some of these new heating and current-drive schemes. This paper reports theoretical progress both in modeling absorption and current drive for intense pulses and in analyzing some of the possible complications that may arise, e.g., parametric instabilities and nonlinear self-focusing. 22 refs., 9 figs., 1 tab

  7. Beam Tests of a Prototype Stripline Beam Position Monitoring System for the Drive Beam of the CLIC Two-beam Module at CTF3

    CERN Document Server

    Benot-Morell, Alfonso; Nappa, Jean-Marc; Vilalte, Sebastien; Wendt, Manfred

    2016-01-01

    In collaboration with LAPP and IFIC, two units of a prototype stripline Beam Position Monitor (BPM) for the CLIC Drive Beam (DB), and its associated readout electronics have been successfully installed and tested in the Two-Beam-Module (TBM) at the CLIC Test Facility 3 (CTF3) at CERN. This paper gives a short overview of the BPM system and presents the performance measured under different Drive Beam configurations.

  8. Momentum transfer through Landau damping and radio frequency current drive

    International Nuclear Information System (INIS)

    The current drive generated by radio frequency waves is regarded as the momentum transfer from waves to resonant electrons through the Landau damping process. The momentum transfer is evaluated using a well-defined model of Landau damping and the plasma current is formulated from the computation between the acceleration by the effective force acting on electrons and the collision. A deformed distribution function to yield the plasma current is formulated with a Boltzmann equation including a simple collision term. This is the basis of the first order current drive theory at the linear Landau damping. (author)

  9. Combined kinetic and transport modeling of radiofrequency current drive

    International Nuclear Information System (INIS)

    A numerical model for predictive simulations of radiofrequency current drive in magnetically confined plasmas is developed. It includes the minimum requirements for a self consistent description of such regimes, i.e., a 3-D ,kinetic equation for the electron distribution function, 1-D heat and current transport equations, and resonant coupling between velocity space and configuration space dynamics, through suitable wave propagation equations. The model finds its full application in predictive studies of complex current profile control scenarios in tokamaks, aiming at the establishment of internal transport barriers by the simultaneous use of various radiofrequency current drive methods. The basic properties of this non-linear numerical system are investigated and illustrated by simulations applied to reversed magnetic shear regimes obtained by Lower Hybrid and Electron Cyclotron current drive for parameters typical of the Tore Supra tokamak. (authors)

  10. Stability, energetic particles, waves, and current drive summary

    International Nuclear Information System (INIS)

    This is the summary paper for the subjects of plasma stability, energetic particles, waves, and current drive for the 20th IAEA Fusion Energy Conference, 1-6 November 2004, Vilamoura, Portugal. Material summarized herein was drawn from 65 contributed papers and 21 overview papers. The distribution of contributed papers by subjects is shown. Significant advances were reported on the principal instabilities in magnetically confined plasmas, even looking forward to the burning plasma state. Wave-plasma physics is maturing and novel methods of current drive and noninductive current generation are being developed. (author)

  11. Fast wave current drive in DIII-D

    International Nuclear Information System (INIS)

    The non-inductive current drive from fast Alfven waves launched by a directional four-element antenna was measured in the DIII-D tokamak. The fast wave frequency (60 MHz) was eight times the deuterium cyclotron frequency at the plasma center. An array of rf pickup loops at several locations around the torus was used to verify the directivity of the four-element antenna. Complete non-inductive current drive was achieved using a combination of fast wave current drive (FWCD) and electron cyclotron current drive (ECCD) in discharges for which the total plasma current was inductively ramped down from 400 to 170 kA. For discharges with steady plasma current, up to 110 kA of FWCD was inferred from an analysis of the loop voltage, with a maximum non-inductive current (FWCD, ECCD, and bootstrap) of 195 out of 310 kA. The FWCD efficiency increased linearly with central electron temperature. For low current discharges, the FWCD efficiency was degraded due to incomplete fast wave damping. The experimental FWCD was found to agree with predictions from the CURRAY ray-tracing code only when a parasitic loss of 4% per pass was included in the modeling along with multiple pass damping

  12. Advanced induction motor drive control with single current sensor

    Directory of Open Access Journals (Sweden)

    Adžić Evgenije M.

    2016-01-01

    Full Text Available This paper proposes induction motor drive control method which uses minimal number of sensors, providing only DC-link current as a feedback signal. Improved DC-link current sampling scheme and modified asymmetrical switching pattern cancels characteristic waveform errors which exist in all three reconstructed motor line-currents. Motor linecurrent harmonic content is reduced to an acceptable level, eliminating torque and speed oscillations which were inherent for conventional single sensor drives. Consequently, use of single current sensor and line-current reconstruction technique is no longer acceptable only for low and medium performance drives, but also for drives where priority is obtaining a highly accurate, stable and fast response. Proposed control algorithm is validated using induction motor drive hardware prototype based on TMS320F2812 digital signal processor. [Projekat Ministarstva nauke Republike Srbije, br. III 042004 and by the Provincial Secretariat for Science and Technological Development of AP Vojvodina under contract No. 114-451-3508/2013-04

  13. Status of the Stripline Beam Position Monitor developement for the CLIC Drive Beam

    CERN Document Server

    Benot-Morell, A; Wendt, M; Faus-Golfe, A; Nappa, J M; Vilalte, S; Smith, S

    2013-01-01

    In collaboration with SLAC, LAPP and IFIC, a first prototype of a stripline Beam Position Monitor (BPM) for the CLIC Drive Beam and its associated readout electronics has been successfully tested in the CLIC Test Facility linac (CTF3) at CERN. In addition, a modified prototype with downstream terminated striplines is under development to improve the suppression of unwanted RF signal interference. This paper presents the results of the beam tests, and the most relevant aspects for the modified stripline BPM design and its expected improvements.

  14. Current drive experiments in the Helicity Injected Torus - II

    Science.gov (United States)

    Hamp, W. T.; Redd, A. J.; Jarboe, T. R.; Nelson, B. A.; O'Neill, R. G.; Raman, R.; Sieck, P. E.; Smith, R. J.; Mueller, D.

    2006-10-01

    The HIT-II spherical torus (ST) device has demonstrated four toroidal plasma current drive configurations to form and sustain a tokamak: 1) inductive (ohmic) current drive, 2) coaxial helicity injection (CHI) current drive, 3) CHI initiated plasmas with ohmic sustainment (CHI+OH), and 4) ohmically initiated plasmas with CHI edge current drive (OH+ECD). CHI discharges with a sufficiently high ratio of injector current to toroidal field current form a closed flux core, and amplify the injector poloidal flux through magnetic reconnection. CHI+OH plasmas are more robust than unassisted ohmic discharges, with a wider operating space and more efficient use of the transformer Volt-seconds. Finally, edge CHI can enhance the plasma current of an ohmic discharge without significantly degrading the quality of the discharge. Results will be presented for each HIT-II operating regime, including empirical performance scalings, applicable parametric operating spaces, and requirements to produce these discharges. Thomson scattering measurements and EFIT simulations are used to evaluate confinement in several representative plasmas. Finally, we outline extensions to the HIT-II CHI studies that could be performed with NSTX, SUNIST, or other ST devices.

  15. Joint Czechoslovak-Soviet workshop on current drive in tokamaks

    International Nuclear Information System (INIS)

    At the Joint Czechoslovak-Soviet Workshop on Current Drive in Tokamaks, five papers dealing with issues of general interest were presented. In a theoretical paper by Klima and Pavlo a one-dimensional model of the lower-hybrid current drive is described and the results of its analysis are used in a numerical simulation using T-7 tokamak parameters. In the second theoretical paper by Vojtsekhovich, Parail and Pereverzev the influence of the LH wave spectrum on the efficiency of the current drive is studied. Two papers deal with a new microwave system designed for experiments on LHCD in the T-7 tokamak. In particular, the power spectra of new four-waveguide grills are computed. In the last paper the non-inductive start-up of the discharge in the T-7 tokamak by means of electron cyclotron waves is investigated. (J.U.)

  16. Electron-cyclotron resonance heating and current drive

    International Nuclear Information System (INIS)

    A brief summary of the theory and experiments on electron-cyclotron heating and current drive is presented. the general relativistic formulation of wave propagation and linear absorption is considered in some detail. The O-mode and the X-mode for normal and oblique propagation are investigated and illustrated by several examples. The experimental verification of the theory in T-10 and D-III-D is briefly discussed. Quasilinear evolution of the momentum distribution and related applications as, for instance, non linear wave damping and current drive, are also considered for special cases of wave frequencies, polarization and propagation. In the concluding section we present the general formulation of the wave damping and current drive in the absence of electron trapping for arbitrary values of the wave frequency. (author) 8 fig. 13 ref

  17. Achromatic beam transport of High Current Injector

    Science.gov (United States)

    Kumar, Sarvesh; Mandal, A.

    2016-02-01

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

  18. Radio Frequency Current Drive Considerations for Small Aspect Ratio Tori

    International Nuclear Information System (INIS)

    Noninductive current drive is required during plasma initiation and for current sustainment in the National Spherical Torus Experiment (NSTX). In this paper, the physics of high harmonic fast waves (HHFW) and the design of an antenna system for NSTX are considered using numerical models. For high current discharges in NSTX, the static magnetic field component in the poloidal direction varies widely during the discharge and can become comparable to the toroidal component in NSTX. Therefore, they calculate the plasma loading for a broad range of antenna and plasma geometries in a three-dimensional model, so that the results can be used to influence the antenna design. Two-dimensional calculations of the wave propagation and absorption in the core plasma indicate that the theoretical current drive efficiency for HHFW can be high, and a general survey of parameters gives a good target for the antenna design. The current drive efficiency calculation is sensitive to the equilibrium model because finite beta effects can substantially alter the calculation of the trapped particle fraction. Traditional methods of toroidally phasing an antenna array as well as poloidal phasing are studied to optimize the current drive efficiency for a range of equilibria. Non-zero poloidal model excitation is also found to affect the antenna performance and flexibility. Performance expectations for a preliminary antenna design are given

  19. Waveguide coupling during lower hybrid current drive in a tokamak

    International Nuclear Information System (INIS)

    During lower hybrid current drive, changes in amplitude and phase of reflected signals at the four waveguide grill, and also decreases in the edge plasma density measured by double probes are monitored. The influence of plasma density and its gradient at the grill mouth on the coupling between waveguides and plasma is investigated by a simplified linear grill theory based on a step plus ramp density model. It is confirmed from the comparison with the theoretical analysis that the change in waveguide coupling during current drive is mainly caused by a reduction of density in the scrape-off plasma. (author)

  20. ELECTRON CYCLOTRON CURRENT DRIVE EFFICIENCY IN GENERAL TOKAMAK GEOMETRY

    International Nuclear Information System (INIS)

    Green's-function techniques are used to calculate electron cyclotron current drive (ECCD) efficiency in general tokamak geometry in the low-collisionality regime. Fully relativistic electron dynamics is employed in the theoretical formulation. The high-velocity collision model is used to model Coulomb collisions and a simplified quasi-linear rf diffusion operator describes wave-particle interactions. The approximate analytic solutions which are benchmarked with a widely used ECCD model, facilitate time-dependent simulations of tokamak operational scenarios using the non-inductive current drive of electron cyclotron waves

  1. Numerical analysis on the synergy between electron cyclotron current drive and lower hybrid current drive in tokamak plasmas

    International Nuclear Information System (INIS)

    The synergy between electron cyclotron current drive (ECCD) and lower hybrid current drive (LHCD) is investigated numerically with the parameters of the HL-2A tokamak. Based on the understanding of the synergy mechanisms, a high current driven efficiency or a desired radial current profile can be achieved through properly matching the parameters of ECCD and LHCD due to the flexibility of ECCD. Meanwhile, it is found that the total current driven by the electron cyclotron wave (ECW) and the lower hybrid wave (LHW) simultaneously can be smaller than the sum of the currents driven by the ECW and LHW separately, when the power of the ECW is much larger than the LHW power. One of the reasons leading to this phenomenon (referred to as negative synergy in this context) is that fast current-carrying electrons tend to be trapped, when the perpendicular velocity driven by the ECW is large and the parallel velocity decided by the LHW is correspondingly small. (paper)

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

    Science.gov (United States)

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

    2015-01-01

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

  3. Numerical modeling of lower hybrid heating and current drive

    International Nuclear Information System (INIS)

    The generation of currents in toroidal plasma by application of waves in the lower hybrid frequency range involves the interplay of several physical phenomena which include: wave propagation in toroidal geometry, absorption via wave-particle resonances, the quasilinear generation of strongly nonequilibrium electron and ion distribution functions, and the self-consistent evolution of the current density in such a nonequilibrium plasma. We describe a code, LHMOD, which we have developed to treat these aspects of current drive and heating in tokamaks. We present results obtained by applying the code to a computation of current ramp-up and to an investigation of the possible importance of minority hydrogen absorption in a deuterium plasma as the ''density limit'' to current drive is approached

  4. Disturbance observer based current controller for vector controlled IM drives

    DEFF Research Database (Denmark)

    Teodorescu, Remus; Dal, Mehmet

    induction motor (IM) drives. The control design, based on synchronously rotating d-q frame model of the machine, has a simple structure that combines the proportional portion of a conventional PI control and output of the observer. The observer is predicted to estimate the disturbances caused by parameters......In order to increase the accuracy of the current control loop, usually, well known parameter compensation and/or cross decoupling techniques are employed for advanced ac drives. In this paper, instead of using these techniques an observer-based current controller is proposed for vector controlled...... change in current control loop and, also to remove undesired cross coupling existing between components of the stator current. The observer uses the measured stator currents and estimated PWM voltages, and produces a disturbance signal with a low pass filter. The proposed control scheme reduces cross...

  5. Direct drive and eddy-current septum magnets

    International Nuclear Information System (INIS)

    Two types of thin septum magnets, direct drive and eddy current, were compared mainly in 2-D magnetic aspects. For the direct-drive type, the leakage field depended on the finite permeability of the magnet core and not on the thickness of the septum conductor. It was suggested that the leakage field be controlled by reducing the current in the septum conductor or by using a correction coil. There were no significant differences between the two types regarding thermal problems caused by high current densities in the thin septa. The leakage fields with 2-mm septum thicknesses were calculated using OPERA-2d to compare the two types. For the eddy-current type, the leakage fields calculated using OPERA-2d were compared with the calculations from Halbach's model. The leakage fields for the eddy-current type decayed with long time constants

  6. Numerical modeling of lower hybrid heating and current drive

    Energy Technology Data Exchange (ETDEWEB)

    Valeo, E.J.; Eder, D.C.

    1986-03-01

    The generation of currents in toroidal plasma by application of waves in the lower hybrid frequency range involves the interplay of several physical phenomena which include: wave propagation in toroidal geometry, absorption via wave-particle resonances, the quasilinear generation of strongly nonequilibrium electron and ion distribution functions, and the self-consistent evolution of the current density in such a nonequilibrium plasma. We describe a code, LHMOD, which we have developed to treat these aspects of current drive and heating in tokamaks. We present results obtained by applying the code to a computation of current ramp-up and to an investigation of the possible importance of minority hydrogen absorption in a deuterium plasma as the ''density limit'' to current drive is approached.

  7. Oscillating Field Current Drive in the Reversed Field Pinch.

    Science.gov (United States)

    Scardovelli, Ruben Angelo Ugo

    Oscillating Field Current Drive (OFCD) was originally proposed as a means of maintaining a quasi steady-state plasma current in a RFP without building up the magnetizing flux threading the central hole of the torus. The MHD dynamics of OFCD is analyzed using a combination of a 1 -D transport code, a linear resistive MHD stability model, and Kadomtsev nonlinear global reconnection model. Using Faraday's law, Ohm's law and on-axis regularity conditions, it it shown that m = 1 modes are necessary for current drive, within the resistive MHD model. A class of m = 1 tearing modes that nonlinearly generate poloidal flux (a necessary condition for current drive) has been identified. These modes are destabilized by off-axis current peaks. A scoping study of the F-Theta^ace has been undertaken to determine quantitatively the effectiveness of this class of tearing modes as a current drive mechanism. Results indicate that equilibria do exist, in regions of the F-Theta space that are easily accessible experimentally, that can yield significant amounts of poloidal flux generation without seriously deteriorating the confinement. A scenario of the OFCD oscillations has been developed in terms of the evolution of the safety factor profile, by considering the stability of the RFP to current-driven tearing modes. The alternating compression and expansion of the plasma during the oscillations have been associated to two different classes of m = 1 tearing modes: the compression to modes driven by off-axis current peaks, that generate poloidal flux; the expansion to instabilities driven by on-axis current peaks, that generate toroidal flux. Transport simulations of the single-circuit oscillations indicate that the RFP "dynamo" is definitely present during half of the oscillation period, while the other half cycle exhibits only small off-axis current peaks at best. Simulations of the two-circuit oscillations with a high current indicate, besides the dynamo, the presence of large off

  8. Charged particle beam current monitoring tutorial

    International Nuclear Information System (INIS)

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

  9. Oscillating field current drive in the reversed field pinch

    International Nuclear Information System (INIS)

    Oscillating Field Current Drive (OFCD) was originally proposed as a means of maintaining a quasi steady-state plasma current in a RFP without building up the magnetizing flux threading the central hole of the torus. The MHD dynamics of OFCD is analyzed using a combination of a 1-D transport code, a linear resistive MHD stability model, and Kadomtsev nonlinear global reconnection model. Using Faraday's law, Ohm's law and on-axis regularity conditions, it is shown that m = 1 modes are necessary for current drive, within the resistive MHD model. A class of m = 1 tearing modes that nonlinearly generate poloidal flux (a necessary condition for current drive) has been identified. These modes are destabilized by off-axis current peaks. A scoping study of the F-θ space has been undertaken to determine quantitatively the effectiveness of this class of tearing modes as a current drive mechanism. Results indicate that equilibria do exist, in regions of the F-θ space that are easily accessible experimentally, that can yield significant amounts of poloidal flux generation without seriously deteriorating the confinement. A scenario of the OFCD oscillations has been developed in terms of the evolution of the safety factor profile, by considering the stability of the RFP to current-driven tearing modes. The alternating compression and expansion of the plasma during the oscillations have been associated to two different classes of m = 1 tearing modes: the compression to modes driven by off-axis current peaks, that genera poloidal flux; the expansion to instabilities driven by on-axis current peaks, that generate toroidal flux. 76 refs., 34 figs., 5 tabs

  10. Alternating-Current Motor Drive for Electric Vehicles

    Science.gov (United States)

    Krauthamer, S.; Rippel, W. E.

    1982-01-01

    New electric drive controls speed of a polyphase as motor by varying frequency of inverter output. Closed-loop current-sensing circuit automatically adjusts frequency of voltage-controlled oscillator that controls inverter frequency, to limit starting and accelerating surges. Efficient inverter and ac motor would give electric vehicles extra miles per battery charge.

  11. DRIVING CURRENTS FOR FLUX ROPE CORONAL MASS EJECTIONS

    International Nuclear Information System (INIS)

    We present a method for measuring electrical currents enclosed by flux rope structures that are ejected within solar coronal mass ejections (CMEs). Such currents are responsible for providing the Lorentz self-force that propels CMEs. Our estimates for the driving current are based on measurements of the propelling force obtained using data from the LASCO coronagraphs aboard the SOHO satellite. We find that upper limits on the currents enclosed by CMEs are typically around 1010 A. We estimate that the magnetic flux enclosed by the CMEs in the LASCO field of view is a few times 1021 Mx.

  12. Enhanced Lower Hybrid Current Drive Experiments on HT-7 Tokamak

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Effective Lower Hybrid Current Driving (LHCD) and improved confinement exper-iments in higher plasma parameters (Ip > 200 kA, ne> 2×1013 cm-3, Te ≥ 1 keⅤ) havebeen curried out in optimized LH wave spectrum and plasma parameters in HT-7 supercon-ducting tokamak. The dependence of current driving efficiency on LH power spectrum, plasmadensity ne and toroidal magnetic field BT has been obtained under optimal conditions. A goodCD efficiency was obtained at higher plasma current and higher electron density. The improve-ment of the energy confinement time is accompanied with the increase in line averaged electrondensity, and in ion and electron temperatures. The highest current driving efficiency reachedηCD = IpneR/PRF ≈ 1.05 × 1019 Am-2/W. Wave-plasma coupling was sustained in a good stateand the reflective coefficient was less than 5%. The experiments have also demonstrated the abilityof LH wave in the start-up and ramp-up of the plasma current. The measurement of the temporaldistribution of plasma parameter shows that lower hybrid leads to a broader profile in plasmaparameter. The LH power deposition profile and the plasma current density profile were modeledwith a 2D Fokker-Planck code corresponding to the evolution process of the hard x-ray detectorarray.

  13. Study of lower hybrid current drive for the demonstration reactor

    Energy Technology Data Exchange (ETDEWEB)

    Molavi-Choobini, Ali Asghar [Dept. of Physics, Faculty of Engineering, Islamic Azad University, Shahr-e-kord Branch, Shahr-e-kord (Iran, Islamic Republic of); Naghidokht, Ahmed [Dept. of Physics, Urmia University, Urmia (Iran, Islamic Republic of); Karami, Zahra [Dept. of Engineering, Islamic Azad University, Zanjan Branch, Zanjan (Iran, Islamic Republic of)

    2016-06-15

    Steady-state operation of a fusion power plant requires external current drive to minimize the power requirements, and a high fraction of bootstrap current is required. One of the external sources for current drive is lower hybrid current drive, which has been widely applied in many tokamaks. Here, using lower hybrid simulation code, we calculate electron distribution function, electron currents and phase velocity changes for two options of demonstration reactor at the launched lower hybrid wave frequency 5 GHz. Two plasma scenarios pertaining to two different demonstration reactor options, known as pulsed (Option 1) and steady-state (Option 2) models, have been analyzed. We perceive that electron currents have major peaks near the edge of plasma for both options but with higher efficiency for Option 1, although we have access to wider, more peripheral regions for Option 2. Regarding the electron distribution function, major perturbations are at positive velocities for both options for flux surface 16 and at negative velocities for both options for flux surface 64.

  14. COMPASS-D magnetic equilibria with LH and NBI current drive

    Czech Academy of Sciences Publication Activity Database

    Hronová-Bilyková, Olena; Fuchs, Vladimír; Pánek, Radomír; Urban, Jakub; Žáček, František; Stöckel, Jan; Voitsekhovitch, I.; Valovič, M.; Fitzgerald, M.

    2006-01-01

    Roč. 56, suppl.B (2006), B24-B30. ISSN 0011-4626. [Symposium on Plasma Physics and Technology/22nd./. Praha, 26.6.2006-29.6.2006] Institutional research plan: CEZ:AV0Z20430508 Keywords : tokamak * COMPASS-D * magnetic equilibrium * ACCOME code * ASTRA code * Neutral Beam Injection * Low Hybrid Current Drive Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.568, year: 2006

  15. Microstructure cantilever beam for current measurement

    Directory of Open Access Journals (Sweden)

    M.T.E. Khan

    2010-01-01

    Full Text Available Most microelectromechanical systems (MEMS sensors are based on the microcantilever technology, which uses a broad range of design materials and structures. The benefit ofMEMStechnology is in developing devices with a lower cost, lower power consumption, higher performance and greater integration. A free-end cantilever beam with a magnetic material mass has been designed using MEMS software tools. The magnetic material was used to improve the sensitivity of the cantilever beam to an externally-applied magnetic field. The cantilever was designed to form a capacitance transducer, which consisted of variable capacitance where electrical and mechanical energies were exchanged. The aim of this paper was to analyse the system design of the microcantilever when subjected to a magnetic field produced by a current-carrying conductor. When the signal, a sinusoidal current with a constant frequency, was applied, the cantilever beam exhibited a vibration motion along the vertical axis when placed closer to the line current. This motion created corresponding capacitance changes and generated a voltage output proportional to the capacitive change in the signal-processing circuitry attached to the microcantilever. The equivalent massspring system theory was used to describe and analyse the effect of the natural frequency of the system vibrations and motion due to the applied magnetic field, in a single-degree of freedom. The main application of this microcantilever is in current measurements to develop a non-contact current sensor mote.

  16. On-axis current drive experiment using a quasi-optical Electron Cyclotron Heating/Current Drive system on the WT-3 tokamak

    International Nuclear Information System (INIS)

    An 89 GHz quasi-optical Electron Cyclotron Heating (ECH)/Current Drive (ECCD) system has been installed on the WT-3 tokamak. In order to investigate the effect of localized ECH/ECCD on the MHD instabilities, this system is designed to focus the micro-wave beam into a small focal spot with the radius about 1 cm in the plasma center. This radius is smaller than the inversion radius of the sawtooth oscillation observed in WT-3. Utilizing this feature, the experiment on control of sawtooth oscillation by on-axis current drive have been performed. Stabilization of sawtooth by counter-ECCD is observed when the power deposition is localized inside the inversion radius. This result may be due to the decrease in current density near the magnetic axis. For the optimal coupling of the micro-wave to obliquely propagating waves at the plasma surface, a linear-elliptical polarization converter has been installed recently. This polarization converter may raise the effective current drive efficiency by a factor of 1.5 for the injected micro-wave power. (author)

  17. High Current Beam Transport to SIS18

    CERN Document Server

    Richter, S; Dahl, L; Glatz, J; Groening, L; Yaramishev, S

    2004-01-01

    The optimized transversal and longitudinal matching of space charged dominated ion beams to SIS18 is essential for a loss free injection. This paper focuses on the beam dynamics in the transfer line (TK) from the post-stripper accelerator to the SIS18. Transverse beam emittance measurements at different positions along the TK were done. Especially, the different foil stripping modes were investigated. A longitudinal emittance measurement set-up was commissioned at the entry to the TK. It is used extensively to tune all the rebunchers along the UNILAC. An addition, a test bench is in use for measurements of longitudinal bunch profiles, which enables to monitor for the final debunching to SIS18. Multi particle simulations by means of PARMILA allow a detailed analysis of experimental results for different ion currents.

  18. Current drive at plasma densities required for thermonuclear reactors.

    Science.gov (United States)

    Cesario, R; Amicucci, L; Cardinali, A; Castaldo, C; Marinucci, M; Panaccione, L; Santini, F; Tudisco, O; Apicella, M L; Calabrò, G; Cianfarani, C; Frigione, D; Galli, A; Mazzitelli, G; Mazzotta, C; Pericoli, V; Schettini, G; Tuccillo, A A

    2010-01-01

    Progress in thermonuclear fusion energy research based on deuterium plasmas magnetically confined in toroidal tokamak devices requires the development of efficient current drive methods. Previous experiments have shown that plasma current can be driven effectively by externally launched radio frequency power coupled to lower hybrid plasma waves. However, at the high plasma densities required for fusion power plants, the coupled radio frequency power does not penetrate into the plasma core, possibly because of strong wave interactions with the plasma edge. Here we show experiments performed on FTU (Frascati Tokamak Upgrade) based on theoretical predictions that nonlinear interactions diminish when the peripheral plasma electron temperature is high, allowing significant wave penetration at high density. The results show that the coupled radio frequency power can penetrate into high-density plasmas due to weaker plasma edge effects, thus extending the effective range of lower hybrid current drive towards the domain relevant for fusion reactors. PMID:20975718

  19. Physics of electron cyclotron current drive on DIII-D

    CERN Document Server

    Petty, C C; Harvey, R W; Kinsey, J E; Lao, L L; Lohr, J; Luce, T C; Makowski, M A; Prater, R

    2002-01-01

    OAK A271 PHYSICS OF ELECTRON CYCLOTRON CURRENT DRIVE ON DIII-D. Recent experiments on the DIII-D tokamak have focused on determining the effect of trapped particles on the electron cyclotron current drive (ECCD) efficiency. The measured ECCD efficiency increases as the deposition location is moved towards the inboard midplane or towards smaller minor radius for both co and counter injection. The measured ECCD efficiency also increases with increasing electron density and/or temperature. The experimental ECCD is compared to both the linear theory (Toray-GA) as well as a quasilinear Fokker-Planck model (CQL3D). The experimental ECCD is found to be in better agreement with the more complete Fokker-Planck calculation, especially for cases of high rf power density and/or loop voltage. The narrow width of the measured ECCD profile is consistent with only low levels of radial transport for the current carrying electrons.

  20. Dynamic modelling of tearing mode stabilization by RF current drive

    International Nuclear Information System (INIS)

    The theory of tearing mode stabilization in toroidal plasmas by RF-driven currents that are modulated in phase with the island rotation is investigated. A time scale analysis of the phenomena involved indicates that transient effects, such as finite time response of the driven currents, island rotation during the power pulses, and the inductive response of the plasma, are intrinsically important. A dynamic model of such effects is developed, based on a 3-D Fokker-Planck code coupled to both the electric field diffusion and the island evolution equations. Extensive applications to both Electron Cyclotron and Lower Hybrid current drive in ITER are presented. (author)

  1. An Imposed Dynamo Current Drive Experiment: Demonstration of Confinement

    Science.gov (United States)

    Jarboe, Thomas; Hansen, Chris; Hossack, Aaron; Marklin, George; Morgan, Kyle; Nelson, Brian; Sutherland, Derek; Victor, Brian

    2014-10-01

    An experiment for studying and developing the efficient sustainment of a spheromak with sufficient confinement (current-drive power heats the plasma to its stability β-limit) and in the keV temperature range is discussed. A high- β spheromak sustained by imposed dynamo current drive (IDCD) is justified because: previous transient experiments showed sufficient confinement in the keV range with no external toroidal field coil; recent results on HIT-SI show sustainment with sufficient confinement at low temperature; the potential of IDCD of solving other fusion issues; a very attractive reactor concept; and the general need for efficient current drive in magnetic fusion. The design of a 0.55 m minor radius machine with the required density control, wall loading, and neutral shielding for a 2 s pulse is presented. Peak temperatures of 1 keV and toroidal currents of 1.35 MA and 16% wall-normalized plasma beta are envisioned. The experiment is large enough to address the key issues yet small enough for rapid modification and for extended MHD modeling of startup and code validation.

  2. Current drive by synergy of slow modes in tokamaks

    International Nuclear Information System (INIS)

    Enhancement of lower hybrid current drive in the presence of wave converted ion-ion slow modes is discussed using a one-dimensional quasi-linear equation. The special case in which the slow mode resulting from conversion in a deuterium-hydrogen mixture is absorbed by low energy electrons is considered in detail. In this scheme, the effect of the ion-ion modes is to increase the electron tail density, and the current enhancement is given by the ratio of the parallel velocity distributions with and without mode converted slow modes, calculated at the lower pparallel limit of the lower hybrid (LH) tail. The method of synergy is suited for remote control of the LH fast tail population, and is useful for current drive optimization. The computation also gives some insight into current drive by ion-ion slow modes in the absence of LH waves, a situation of relevance in a high temperature plasma where LH accessibility is severely reduced. (author). 8 refs, 5 figs

  3. System studies of rf current drive for MST

    International Nuclear Information System (INIS)

    Two rf schemes are being studied on the MST reversed field pinch for their potential in current profile control experiments. MHD modeling has shown that a substantial externally-driven off axis parallel current can improve stability of the dominant core tearing modes. A radially localized axisymmetric population of fast electrons has been observed by SXR emission during LH injection (100kW at 800MHz), and is consistent with CQL3D modeling which predicts a small driven current. Computational work suggests that doubling the input power will statistically improve the LH-induced SXR signal to background ratio, and that about 2MW of injected power (an order of magnitude increase) will drive enough current for stabilization of tearing modes. Additionally, a 1 MW 5.5 GHz electron Bernstein wave (EBW) experiment is under construction, which utilizes a very simple and compact antenna compatible with the demands of the RFP. EBW allows access to electron cyclotron heating and current drive in the overdense plasma. Coupling of the external electromagnetic wave to the EBW has been demonstrated, and initial tests at ∼100kW power have produced a small, localized xray flux consistent with rf heating and high diffusivity of fast electrons. Computational work is currently underway to answer the very important questions of how much power is required, and what level of electron diffusivity is tolerable, to generate a consequential amount of EBW current.

  4. Driving convection by a temperature gradient or a heat current

    OpenAIRE

    Matura, P.; Luecke, M

    2006-01-01

    Bifurcation properties, stability behavior, dynamics, and the heat transfer of convection structures in a horizontal fluid layer that is driven away from thermal equilibrium by imposing a vertical temperature difference are compared with those resulting from imposing a heat current. In particular oscillatory convection that occurs in binary fluid mixtures in the form of travelling and standing waves is determined numerically for the two different driving mechanisms. Conditions are elucidated ...

  5. Brushless DC motor Drive during Speed regulation with Current Controller

    Directory of Open Access Journals (Sweden)

    Bhikshalu Manchala

    2015-04-01

    Full Text Available Brushless DC Motor (BLDC is one of the best electrical drives that have increasing popularity, due to their high efficiency, reliability, good dynamic response and very low maintenance. Due to the increasing demand for compact & reliable motors and the evolution of low cost power semiconductor switches and permanent magnet (PM materials, brushless DC motors become popular in every application from home appliances to aerospace industry. The conventional techniques for controlling the stator phase current in a brushless DC drive are practically effective in low speed and cannot reduce the commutation torque ripple in high speed range. This paper presents the PI controller for speed control of BLDC motor. The output of the PI controllers is summed and is given as the input to the current controller. The BLDC motor is fed from the inverter where the rotor position and current controller is the input. The complete model of the proposed drive system is developed and simulated using MATLAB/Simulink software. The operation principle of using component is analysed and the simulation results are presented in this to verify the theoretical analysis.

  6. Current status of the LBNE neutrino beam

    CERN Document Server

    Moore, Craig Damon; Crowley, Cory Francis; Hurh, Patrick; Hylen, James; Lundberg, Byron; Marchionni, Alberto; McGee, Mike; Mokhov, Nikolai V; Papadimitriou, Vaia; Plunkett, Rob; Reitzner, Sarah Diane; Stefanik, Andrew M; Velev, Gueorgui; Williams, Karlton; Zwaska, Robert Miles

    2015-01-01

    The Long Baseline Neutrino Experiment (LBNE) will utilize a neutrino beamline facility located at Fermilab. The facility is designed to aim a beam of neutrinos toward a detector placed in South Dakota. The neutrinos are produced in a three-step process. First, protons from the Main Injector hit a solid target and produce mesons. Then, the charged mesons are focused by a set of focusing horns into the decay pipe, towards the far detector. Finally, the mesons that enter the decay pipe decay into neutrinos. The parameters of the facility were determined by an amalgam of the physics goals, the Monte Carlo modeling of the facility, and the experience gained by operating the NuMI facility at Fermilab. The initial beam power is expected to be ~700 kW, however some of the parameters were chosen to be able to deal with a beam power of 2.3 MW. The LBNE Neutrino Beam has made significant changes to the initial design through consideration of numerous Value Engineering proposals and the current design is described.

  7. Towards fully non-inductive current drive operation in JET

    International Nuclear Information System (INIS)

    Quasi steady operation has been achieved at JET in the high confinement regime with Internal Transport Barriers, ITBs. The ITBs' performances are maintained up to 11 s. This duration, much larger than the energy confinement time, is already approaching a current resistive time. The high performance phase is limited only by plant constraints. The radial profiles of the thermal electron and ion pressures have steep gradients typically at mid-plasma radius. A large fraction of non-inductive current (above 80%) is sustained throughout the high performance phase with a poloidal beta exceeding unity. The safety factor profile plays an important role in sustaining the ITB characteristics. In this regime where the self-generated bootstrap current (up to LOMA) represents 50% of the total current, the resistive evolution of the non-monotonic q-profile is slowed down by using off-axis lower hybrid current drive. (authors)

  8. Current drive by spheromak injection into a tokamak

    OpenAIRE

    Brown, M. R.; Bellan, P. M.

    1990-01-01

    We report the first observation of current drive by injection of a spheromak plasma into a tokamak (Caltech ENCORE small reasearch tokamak) due to the process of helicity injection. After an abrupt 30% increase, the tokamak current decays by a factor of 3 due to plasma cooling caused by the merging of the relatively cold spheromak with the tokamak. The tokamak density profile peaks sharply due to the injected spheromak plasma (n¯3 increases by a factor of 6) then becomes hollow, suggestive of...

  9. Current drive for stability of thermonuclear plasma reactor

    Science.gov (United States)

    Amicucci, L.; Cardinali, A.; Castaldo, C.; Cesario, R.; Galli, A.; Panaccione, L.; Paoletti, F.; Schettini, G.; Spigler, R.; Tuccillo, A.

    2016-01-01

    To produce in a thermonuclear fusion reactor based on the tokamak concept a sufficiently high fusion gain together stability necessary for operations represent a major challenge, which depends on the capability of driving non-inductive current in the hydrogen plasma. This request should be satisfied by radio-frequency (RF) power suitable for producing the lower hybrid current drive (LHCD) effect, recently demonstrated successfully occurring also at reactor-graded high plasma densities. An LHCD-based tool should be in principle capable of tailoring the plasma current density in the outer radial half of plasma column, where other methods are much less effective, in order to ensure operations in the presence of unpredictably changes of the plasma pressure profiles. In the presence of too high electron temperatures even at the periphery of the plasma column, as envisaged in DEMO reactor, the penetration of the coupled RF power into the plasma core was believed for long time problematic and, only recently, numerical modelling results based on standard plasma wave theory, have shown that this problem should be solved by using suitable parameter of the antenna power spectrum. We show here further information on the new understanding of the RF power deposition profile dependence on antenna parameters, which supports the conclusion that current can be actively driven over a broad layer of the outer radial half of plasma column, thus enabling current profile control necessary for the stability of a reactor.

  10. High gain free electron laser for heating and current drive in the ALCATOR-C tokamak

    International Nuclear Information System (INIS)

    The free electron laser (FEL) particle simulation code, FRED, has been used to examine the design of an FEL for amplifying radiation in the one to two millimeter wavelength range for use in electron heating and current drive in a tokamak device such as ALCATOR-C. As a desired design goal a peak output power of 8 GW, with a minimum input power in the 1 to 100 watt range has been used. The effects of electron beam current, energy and brightness, laser frequency and input power as well as wiggler wavelength and overall wiggler length on the performance of the FEL have been examined

  11. Sustainment of spheromak plasma by driving the toroidal current

    International Nuclear Information System (INIS)

    Spheromak plasma productions by means of quasi-static method on the basis of z-discharge and theta-discharge have been investigated using the machine named TS-3. This machine consists of a SUS vacuum vessel with an inner diameter of 76 cm and an axial length of 95 cm, two internal poloidal coils enclosed with SUS thin cases with a major diameter of 43 cm and an axial separation of 39 cm, and two sets of eight pairs of electrodes around each poloidal coil. Up to 0.2 T vertical magnetic field can be applied using an external DC mirror type magnet. Either one or two isolated spheromak(s) can be generated by the selection of sets of electrodes in proper manner. An optional current transformer with an outer cylinder diameter of 9 cm installed along the major symmetric axis of the vessel enables us to perform toroidal current driving of spheromak plasma. Spheromak plasmas produced in He has of about 10 mTorr have a decay time of about 30 micro sec. with the center conductor when it has no current for the toroidal current driving. However, when a flux change of 30 to 60 Wb/s is given to the center coil during 100 micro sec after the initiation of the spheromak configuration, the sustainment of the configuration is observed by the measurement of both poloidal and toroidal field spatial profile

  12. Radio frequency current drive for small aspect ratio tori

    International Nuclear Information System (INIS)

    Non-inductive current drive (CD) is required during plasma initiation and for current sustainment in NSTX. The physics of high harmonic fast waves (HHFW) and the design of an antenna system for NSTX are studied. It is found that the theoretical current drive efficiency for HHFW can be high, and a general survey of parameters gives a good target for the antenna design. The primary issue for HHFW during plasma initiation is loading since the CD efficiency is very high for low density plasmas. For high beta operation at full current launching in the usual manner from the equatorial plane may lead to marginal CD performance. However, advanced antenna designs exploiting the theoretical results show some promise for high beta operation. Two methods to optimize the CD efficiency have been explored. The first non-zero poloidal mode excitation, provides enhanced efficiency because of improved penetration and a reduction of detrimental trapped particle effects. A second, placement of the antenna away from the equatorial plane, can also be used to reduce trapped particle effects. These methods can be used separately or together, yielding potential improvements of more than a factor of 2 in CD efficiency for NSTX

  13. Penetration of lower hybrid current drive waves in tokamaks

    International Nuclear Information System (INIS)

    Lower hybrid (LH) ray propagation in toroidal plasma is shown to be controlled by combination of the azimuthal spectrum launched by the antenna, the poloidal variation of the magnetic field, and the scattering of the waves by the drift wave fluctuations. The width of the poloidal and radial radio frequency wave spectrum increases rapidly as the rays penetrate into higher density and scatter from the drift waves. The electron temperature gradient (ETG) spectrum is particularly effective in scattering the LH waves due to its comparable wavelengths and phase velocities. ETG turbulence is also driven by the radial gradient of the electron current profile giving rise to an anomalous viscosity spreading the LH driven plasma currents. The LH wave scattering is derived from a Fokker-Planck equation for the distribution of the ray trajectories with diffusivities derived from the drift wave fluctuations. The condition for chaotic diffusion for the rays is derived. The evolution of the poloidal and radial mode number spectrum of the lower hybrid waves are both on the antenna spectrum and the spectrum of the drift waves. Antennas launching higher poloidal mode number spectra drive off-axis current density profiles producing negative central shear [RS] plasmas with improved thermal confinement from ETG transport. Core plasma current drive requires antennas with low azimuthal mode spectra peaked at m = 0 azimuthal mode numbers

  14. Penetration of lower hybrid current drive waves in tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Horton, W. [The University of Texas at Austin, Austin, Texas 78712 (United States); Aix-Marseille University, 58, Bd Charles Livon, 13284 Marseille (France); Goniche, M.; Peysson, Y.; Decker, J.; Ekedahl, A.; Litaudon, X. [CEA, IRFM, F-13108 Saint-Paul-Lez Durance (France)

    2013-11-15

    Lower hybrid (LH) ray propagation in toroidal plasma is shown to be controlled by combination of the azimuthal spectrum launched by the antenna, the poloidal variation of the magnetic field, and the scattering of the waves by the drift wave fluctuations. The width of the poloidal and radial radio frequency wave spectrum increases rapidly as the rays penetrate into higher density and scatter from the drift waves. The electron temperature gradient (ETG) spectrum is particularly effective in scattering the LH waves due to its comparable wavelengths and phase velocities. ETG turbulence is also driven by the radial gradient of the electron current profile giving rise to an anomalous viscosity spreading the LH driven plasma currents. The LH wave scattering is derived from a Fokker-Planck equation for the distribution of the ray trajectories with diffusivities derived from the drift wave fluctuations. The condition for chaotic diffusion for the rays is derived. The evolution of the poloidal and radial mode number spectrum of the lower hybrid waves are both on the antenna spectrum and the spectrum of the drift waves. Antennas launching higher poloidal mode number spectra drive off-axis current density profiles producing negative central shear [RS] plasmas with improved thermal confinement from ETG transport. Core plasma current drive requires antennas with low azimuthal mode spectra peaked at m = 0 azimuthal mode numbers.

  15. Initial results of lower hybrid current drive experiment on JT-60

    International Nuclear Information System (INIS)

    The initial results of current drive experiment by lower hybrid range of frequencies (LHRF) on JT-60 are reported. This experiment is a first trial of RF current drive on a reactor grade tokamak. As the result, the current of 1.7 MA is driven by LHRF with the power of 1.2 MW (2.0 GHz) at the density n-bare = 0.3 x 1019 m-3. The efficiency of current drive ηCD(≡ n-bare(1019 m-3)IRF(MA)R(m)/PRF(MW)) is 0.7 ∼ 1.7. When neutral beams are combined with LHRF, ηCD increased to 2.0 ∼ 2.8. Furthermore, current ramp up and recharging were carried out. The efficiencies of current ramp up and recharging are approximately 0.2 for both. Also, the suppression of soft X-ray sawtooth signals is recognized, as obserbed on middle sized tokamak. (author)

  16. Pushing beam currents to the limit

    International Nuclear Information System (INIS)

    One of the cyclotron systems running at the Nordion Int. radioisotope production facility at TRIUMF is the EBCO TR30. This cyclotron produces up to 250μA on each of two beamlines simultaneously. Two solid (for the production of 201Tl, 57Co, 67Ga and 111In) and a gaseous (for producing 123I) target station are in routine operation on this facility. Since future projections indicate a greater demand for reliable radioisotope production there is a program underway to increase the output of the facility to double the present level. One way that this is being achieved is through a careful thermal analysis of the the solid target system to maximize its performance. In conjunction with this we have developed and tested a 500μA upgrade of our solid target system. Gas targets are being investigated for possible ways of increasing the efficiency of production via rotating/sweeping beams which allow higher beam currents. Finally, the TR30 cyclotron is being upgraded to deliver 50-100% more beam on target. By pushing both the cyclotron and target technology to the limit we will be able to produce significantly higher levels of radioisotopes than many other comparable facilities. (author) 11 refs., 3 figs

  17. The PHIN photoinjector for the CTF3 Drive beam

    CERN Document Server

    Losito, R; Braun, H; Champault, N; Chevallay, E; Divall, M; Fedosseev, V; Hirst, G; Kumar, A; Kurdi, G; Martin, W; Masi, A; Mercier, B; Musgrave, I; Prevost, C; Ross, I; Roux, R; Springate, E; Suberlucq, Guy

    2006-01-01

    A new photoinjector for the CTF3 drive beam has been designed and is now being constructed by a collaboration among LAL, CCLRC and CERN within PHIN, the second Joint Research Activity of CARE. The photoinjector will provide a train of 2332 pulses at 1.5 GHz with a complex timing structure (sub-trains of 212 pulses spaced from one another by 333 ps or 999 ps) to allow the frequency multiplication scheme, which is one of the features of CLIC, to be tested in CTF3. Each pulse of 2.33 nC will be emitted by a Cs2Te photocathode deposited by a co-evaporation process to allow high quantum efficiency in operation (>3% for a minimum of 40 h). The 3 GHz, 2 1/2 cell RF gun has a 2 port coupler to minimize emittance growth due to asymmetric fields, racetrack profile of the irises and two solenoids to keep the emittance at the output below 20 p.mm.mrad. The laser has to survive very high average powers both within the pulse train (15 kW) and overall (200 W before pulse slicing). Challenging targets are also for amplitude ...

  18. Emittance optimisation in the Drive Beam Recombination Complex at CTF3

    CERN Document Server

    Gamba, D

    2014-01-01

    According to the Conceptual Design Report, the power to accelerate the main colliding beams of CLIC is taken from parallel high intensity (100 A), low energy (2.37 GeV) beams. These beams are generated by long trains, accelerated by conventional klystrons and then time-compressed in the so called Drive-Beam Recombination Complex (DBRC). A scaled version of the DBRC has been built at the CLIC Test Facility (CTF3) at CERN in order to prove its principle and study any arising feasibility issues. One of the main constraints is the emittance control during the recombination process. This work presents an overview of the studies ongoing at CTF3, keeping in view possible improvements of the nominal CLIC design. In particular, a generic feedback algorithm to solve (quasi-)linear systems has been implemented and used in order to optimize the process by tuning the energy of the beam and steer the orbits in the different lines, as well matching the design dispersion. Current results and possible room for further optimiz...

  19. Dependence of EC-driven current on the EC-wave beam direction in LHD

    International Nuclear Information System (INIS)

    Electron cyclotron current drive (ECCD) experiments were conducted in the Large Helical Device to investigate the characteristics of EC-driven current and its profile and the possibility of controlling current and rotational transform profiles by ECCD. Successful ECCD helps prevent magnetohydrodynamic instabilities in plasmas. Scanning the EC-wave beam direction with a long pulse width of 8 s revealed a systematic change in the plasma current. The current's direction was reversed by a reversal of the beam direction. The direction agrees with the prediction of Fisch-Boozer theory regarding EC-wave beam injection from low-field side. The maximum driven current is 9 kA with an EC-wave power of 100 kW. The optimum beam direction that maximizes the driven current is investigated with the help of ray-tracing code. This direction depends on the magnetic field, efficiency of power absorption, and fraction of the power absorbed by trapped electrons. (author)

  20. Drive Current Enhancement in TFET by Dual Source Region

    Directory of Open Access Journals (Sweden)

    Zhi Jiang

    2015-01-01

    Full Text Available This paper presents tunneling field-effect transistor (TFET with dual source regions. It explores the physics of drive current enhancement. The novel approach of dual source provides an effective technique for enhancing the drive current. It is found that this structure can offer four tunneling junctions by increasing a source region. Meanwhile, the dual source structure does not influence the excellent features of threshold slope (SS of TFET. The number of the electrons and holes would be doubled by going through the tunneling junctions on the original basis. The overlap length of gate-source is also studied. The dependence of gate-drain capacitance Cgd and gate-source capacitance Cgs on gate-to-source voltage Vgs and drain-to-source voltage Vds was further investigated. There are simulation setups and methodology used for the dual source TFET (DS-TFET assessment, including delay time, total energy per operation, and energy-delay product. It is confirmed that the proposed TFET has strong potentials for VLSI.

  1. Recent experimental results of KSTAR RF heating and current drive

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S. J., E-mail: sjwang@nfri.re.kr; Kim, J.; Jeong, J. H.; Kim, H. J.; Joung, M.; Bae, Y. S.; Kwak, J. G. [National Fusion Research Institute, Daejoen, 305-806 (Korea, Republic of)

    2015-12-10

    The overview of KSTAR activities on ICRH, LHCD and ECH/CD including the last experimental results and future plan aiming for long-pulse high-beta plasma will be presented. Recently we achieved reasonable coupling of ICRF power to H-mode plasma through several efforts to increase system reliability. Power balance will be discussed on this experiment. LHCD is still struggling in the low power regime. Review of antenna spectrum for the higher coupling in H-mode plasma will be tried. ECH/CD provides 41 sec, 0.8 MW of heating power to support high-performance long-pulse discharge. Also, 170 GHz ECH system is integrated with the Plasma Control System (PCS) for the feedback controlling of NTM. Status and plan of ECH/CD will be discussed. Finally, helicon current drive is being prepared for the next stage of KSTAR operation. The hardware preparation and the calculation results of helicon current drive in KSTAR plasma will be discussed.

  2. Spectral Effects on Fast Wave Core Heating and Current Drive

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-05-11

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

  3. Conceptual Design of the Drive Beam for a PWFA-LC

    Energy Technology Data Exchange (ETDEWEB)

    Pei, S.; Hogan, M.J.; Raubenheimer, T.O.; Seryi, A.; /SLAC; Braun, H.H.; Corsini, R.; Delahaye, J.P.; /DESY

    2009-08-03

    Plasma Wake-Field Acceleration (PWFA) has demonstrated acceleration gradients above 50 GeV/m. Simulations have shown drive/witness bunch configurations that yield small energy spreads in the accelerated witness bunch and high energy transfer efficiency from the drive bunch to the witness bunch, ranging from 30% for a Gaussian drive bunch to 95% for bunch with triangular shaped longitudinal profile. These results open the opportunity for a linear collider that could be compact, efficient and more cost effective than the present microwave technologies. A concept of a PWFA-based Linear Collider (PWFA-LC) has been developed by the PWFA collaboration. Here we will describe the conceptual design and optimization of the drive beam, which includes the drive beam linac and distribution system. We apply experience of the CLIC drive beam design and demonstration in the CLIC Test Facility (CTF3) to this study. We discuss parameter optimization of the drive beam linac structure and evaluate the drive linac efficiency in terms of the drive beam distribution scheme and the klystron/modulator requirements.

  4. Optimized calculation of the synergy conditions between electron cyclotron current drive and lower hybrid current drive on EAST

    Science.gov (United States)

    Wei, Wei; Bo-Jiang, Ding; Y, Peysson; J, Decker; Miao-Hui, Li; Xin-Jun, Zhang; Xiao-Jie, Wang; Lei, Zhang

    2016-01-01

    The optimized synergy conditions between electron cyclotron current drive (ECCD) and lower hybrid current drive (LHCD) with normal parameters of the EAST tokamak are studied by using the C3PO/LUKE code based on the understanding of the synergy mechanisms so as to obtain a higher synergistic current and provide theoretical reference for the synergistic effect in the EAST experiment. The dependences of the synergistic effect on the parameters of two waves (lower hybrid wave (LHW) and electron cyclotron wave (ECW)), including the radial position of the power deposition, the power value of the LH and EC waves, and the parallel refractive indices of the LHW (N∥) are presented and discussed. Project supported by the National Magnetic Confinement Fusion Science Program of China (Grant Nos. 2011GB102000, 2012GB103000, and 2013GB106001), the National Natural Science Foundation of China (Grant Nos. 11175206 and 11305211), the JSPS-NRF-NSFC A3 Foresight Program in the Field of Plasma Physics (Grant No. 11261140328), and the Fundamental Research Funds for the Central Universities of China (Grant No. JZ2015HGBZ0472).

  5. Effects of beam-driven poloidal rotation on the neoclassical bootstrap current

    International Nuclear Information System (INIS)

    Unbalanced neutral beam injection drives toroidal and poloidal rotations in a tokamak plasma. The beam toroidal momentum input drives the toroidal rotation, and the parallel friction between the thermal ions and fast ions induces the poloidal rotation. A theory of the beam-driven poloidal rotation and its effects on energy transport was given recently by Hinton and Kim. In this work, we extend their considerations to the effects on the neoclassical bootstrap current. For parameters of interest in present neutral beam heated tokamaks, the magnitude of the beam-driven poloidal rotation can be significantly larger than that of the standard neoclassical value due to the ion temperature gradient. The presence of this driven poloidal rotation will manifest itself in modification of the neoclassical bootstrap current. In the case of coinjection, the driven poloidal rotation is in the opposite direction to the rotation driven by the temperature gradient, therefore it enhances the bootstrap current. In comparison with the standard theoretical predictions of the neutral beam-driven current, that enhancement in the bootstrap current varies with the beam and plasma parameters. A calculation of the parallel transport coefficients associated with the driven poloidal flow in finite-aspect ratio tokamaks will be presented. Experimental conditions for observing the enhancement in bootstrap current will be discussed

  6. Current profile modification with electron cyclotron current drive in the DIII-D tokamak

    International Nuclear Information System (INIS)

    Proof-of-principle experiments on the suitability of electron cyclotron current drive (ECCS) for active current profile control are reported. Experiments with second harmonic extraordinary mode absorption at power levels near 1 MW have demonstrated ability to modify the current profile. This modification is manifested in changes in the internal inductance and the time at which sawteeth appear. Measurements of the local current density and internal loop voltage using high resolution motional Stark effect spectroscopy to half of the minor radius in discharges with localized deposition clearly demonstrate localized off-axis ECCS at the predicted location. Comparison with theory indicates the detrimental effect of trapped electrons on the current drive efficiency is less than predicted. Modification of the theory for finite collisionality is the leading candidate to explain the observations. (author)

  7. Optimization of the EC Heating and Current Drive Capabilities

    International Nuclear Information System (INIS)

    Full text: A 24 MW CW Electron Cyclotron Heating and Current Drive (EC H&CD) system operating at 170 GHz is to be installed for the ITER tokamak. The ITER EC system will represent a large step forward in the use of microwave systems for plasma heating and current drive applications. Present day systems are operating in relatively short pulses (≤ 10 s) and installed power levels of ≤ 4.5 MW, while the ITER EC system parameters are CW operation and 20 MW injected power. The technical challenge facing the development and installation of the EC system is further complicated due to the harsh ITER in-vessel environment and complicated procurement strategy. The ITER EC international community has confronted these challenges, aiming at integrating the modifications proposed from the 2007 ITER design review and further enhancing the EC system capabilities. These changes have not only simplified the technical design, but have also simplified the procurement interfaces and increased the functional capabilities for plasma heating and current drive applications. The functional improvements include increasing the access of the EC power from ∼ 50% to nearly ∼ 90% of the plasma cross section. In particular the UL has been modified to allow power deposition over the range of ∼ 0.3 ≤ ρΤ ≤ 0.9 compared to previous access of ∼ 0.55 ≤ ρΤ ≤ 0.85 (where ρΤ is the square root of the normalized toroidal flux). This allows the UL to be applicable for a broader access for stabilization of neoclassical tearing modes (NTMs) and sawtooth instability. The EC heating is functionally limited in magnetic field region depending on the resonant harmonic. The heating access in ITER was assumed to be applicable over ∼ 33% of the range from 2.3 T to 5.3 T, regions of fundamental and second harmonics. Recent analysis associated with the EL has demonstrated that the EC system is applicable over a much broader range: ∼ 75% for central heating (ρΤ ≤ 0.5) and ∼ 90% for L

  8. Summary and viewgraphs from the Q-121 US/Japan advanced current drive concepts workshop

    International Nuclear Information System (INIS)

    With the emphasis placed on current drive by ITER, which requires steady state operation in its engineering phase, it is important to bring theory and experiment in agreement for each of the schemes that could be used in that design. Both neutral beam and lower hybrid (LH) schemes are in excellent shape in that regard. Since the projected efficiency of all schemes is marginal it is also important to continue our search for more efficient processes. This workshop featured experimental and theoretical work in each processes. This workshop featured experimental and theoretical work in each of these areas, that is, validation of theory and the search for better ideas. There were a number of notable results to report, the most striking again (as with last year) the long pulse operation of TRIAM-1M. A low current was sustained for over 1 hour with LH waves, using new hall-effect sensors in the equilibrium field circuit to maintain position control. In JT-60, by sharpening the wave spectrum the current drive efficiency was improved to 0.34 x 1020m-2A/W and 1.5 MA of current was driven entirely by the lower hybrid system. Also in that machine, using two different LH frequencies, the H-mode was entered. Finally, by using the LH system for startup they saved 2.5 resistive volt-sec of flux, which if extrapolated to ITER would save 40 volt-sec there. For the first time, and experiment on ECH current drive showed reasonable agreement with theory. Those experiments are reported here by James (LLNL) on the D3-D machine. Substantially lower ECH current drive than expected theoretically was observed on WT-3, but if differed by being in a low absorption regime. Nonetheless, excellent physics results were achieved in the WT-3 experiments, notably in having careful measurements of the parallel velocity distributions

  9. Lower hybrid current drive in the presence of ICRF waves

    International Nuclear Information System (INIS)

    Motivated by recent JET results showing an enhancement in the lower hybrid current drive (LHCD) efficiency in ICRF heated plasmas, the authors have been studying the interaction of lower hybrid generated electron tails with fast Alfven waves (FAW) and ion-Bernstein waves (IBW). The IBW's are generated by mode conversion, at the hybrid resonance layers inside the plasma, of the externally launched FAW's. The numerical solutions of the Fokker-Planck equation using CQL3D show that, for the powers used in JET, the FAW cannot significantly modify the LH electron tail and, consequently, does not play a role in the enhancement of the LHCD efficiency. Similar analysis for IBW's shows that these waves play an important role in the enhancement of the current drive efficiency. Calculations show that for small kparallel's about 20% of the FAW power is mode converted to the IBW's. Previous analysis of the propagation of IBW's has shown that the electric field amplitudes are considerably enhanced as IBW propagate in toroidal plasmas. This compensates for the possibly small fraction of the total input power that mode converts to IBW's. Furthermore, IBW's interact with electrons off-axis through Landau damping on flux surfaces where LHW's generate currents. FAW's only interact with electrons near the ion cyclotron or ion-ion hybrid resonance layers which, in the case of JET, may be near the axis of the plasma while the LH waves damp well off-axis. So IBW's are more likely to enhance the LHCD efficiency. In fact, the conditions for which JET shows an enhancement in LHCD efficiency are those for which mode conversion to IBW's occurs. The authors present detailed analytical and numerical results in support of the statements made above

  10. Stabilization of tearing modes in DIII-D by localized electron cyclotron current drive

    Science.gov (United States)

    Luce, T. C.; La Haye, R. J.; Humphreys, D. A.; Petty, C. C.; Prater, R.

    2001-10-01

    Tearing modes have been shown to limit β and confinement in conventional ELMing H-mode tokamak regimes. The tearing modes grow from a "seed" island due to the destabilizing effect of pressure flattening in the island leading to a reduction in the local bootstrap current. Recent experiments on the DIII-D tokamak have demonstrated stabilization of m=3/n=2 tearing modes in the presence of sawteeth through localized electron cyclotron current drive (ECCD). Variation of the deposition location indicates the ECCD remains localized despite the beam traversing an ELMing edge. The effect of the ECCD on the mode is consistent with predictions that the ECCD must be within the island for stabilization. The calculated EC current density (JEC) is greater than the calculated local bootstrap current density (JBS) also in accord with predictions. A closed-loop feedback scheme has been successfully operated for the first time using position control and magnetic signals as the actuator and sensor, respectively.

  11. Lower-hybrid current drive with opposing ohmic drive on PLT

    International Nuclear Information System (INIS)

    Two distinct conditions where the rf phase velocity is directed opposite to the ohmically induced electron drift have been studied experimentally: (1) rf current ramp-up (f/sub p/ > 0), where an induced electric field opposes the current increase; (2) rf current ramp-down, where waves are launched opposite the electron drift direction for a decaying plasma current. The time behavior of the electron tail is inferred from hard x-ray (30 to 750 keV) emission as a function of angle to B. In cases (1) and (2) we find that the emission amplitude in the reverse (opposite the LH phase velocity) direction increases throughout the rf pulse, while it is constant in the forward direction. This increase indicates that some high energy electrons are accelerated or are even running away in the direction opposite to the main rf produced tail. It also indicates for case (1) that the electric field in the plasma center has been reversed by the rf current drive

  12. Analysis of current driving capability of pentacene TFTs for OLEDs

    Science.gov (United States)

    Ryu, Gi Seong; Byun, Hyun Sook; Xu, Yong Xian; Pyo, Kyung Soo; Choe, Ki Beom; Song, Chung Kun

    2005-01-01

    The flexible display and the application of Roll-To-Roll process is difficult because high temperature process of a-Si;H TFT and poly-Si TFT limited the use of plastic substrate. We proposed AMOLED using Pentacene TFT (OTFT) to fabricate flexible display. The first stage for OTFT application to OLED, we analyzed OTFT as driving device of OLED. The process performed on glass and plastic (PET) substrate that is coated ITO and PVP is used for gate insulator. The field effect mobility of the fabricated OTFT is 0.1~0.3cm2/V"sec and Ion/Ioff current ratio is 103~105. OLED is fabricated with two stories structure of TPD and Alq3, and we can observe the light at 5V by the naked eye. The wavelength of observed lights is 530nm ~550nm. We can confirm the driving of OLED due to OTFT using Test panel and observe OLED control by gate voltage of OTFT. Also, we verify designed structure and process, and make a demonstration fabricating 64 by 64 backplane based on Test panel.

  13. Bootstrap current of fast ions in neutral beam injection heating

    International Nuclear Information System (INIS)

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

  14. EC heating and current drive studies during current ramp-up in Tore Supra

    International Nuclear Information System (INIS)

    Electron cyclotron current drive (ECCD) has been successfully used for current profile tailoring during the current ramp-up in Tore-Supra. Different ECCD scenarios have been compared: with counter-ECCD on axis, high core electron temperatures and steep gradients have been observed, which are maintained for some time on the current flat-top and with the addition of ion cyclotron resonance heating through on-axis (H)D scenarios. There are strong experimental indications that a negative magnetic shear region is produced in the core, confirmed by simulation modelling with the CRONOS code

  15. Electron cyclotron current drive compensation of the bootstrap current in quasi-symmetric reactor devices

    International Nuclear Information System (INIS)

    Previous results have shown that the bootstrap current (BC) can considerably affect the equilibrium and stability of some reactor-size stellarator configurations through its alteration of the rotational transform profile. This suggests that a way to externally compensate the effects of the BC may be needed in order to keep the ι within MHD stable values. The present work is devoted to model the current driven (CD) by an electromagnetic wave in the region where the BC profile needs to be locally altered. The simulations are carried out with the 3D ray-tracing code ART in which an interface with a current drive module based on the solution of the Langevin equations has been implemented. The ensemble calculates the current drive density at each magnetic surface pierced by the ray. The method allows to investigate different launching scenarios (position, wave frequency, input power, polarization, etc.) depending on the amount, localization and magnitude of the current to be induced. Two contrasting configurations have been considered, a 3-period quasi-axisymmetric (QAS) and a 4-period quasi helically-symmetric (QHS), in which the BC affects the rotational transform in opposite ways. In the QAS case, the goal is to induce a counter-current in the vicinity of ρ = 0 .76 where the ι approaches the resonant value ιc = 2/3 value, at β = 6 .4%. A second harmonic X-mode wave launched from a high field region, with 385 GHz of frequency (the configuration has B0 = 4.9 Tesla) and 1.5 MWatt of power has been modeled which drives a current opposite to the BC in the desired location. Both currents together lead to an equilibrium in which the ι is held well beneath the ιc = 2/3 value ensuring that the configuration is stable. In contrast, for the QHS case studied, the idea is to create a current in the same direction as the BC to further decrease the ι near the axis at β = 3%, pushing it away from the ιc = 1 rational value. This has been obtained with a 3rd harmonic X

  16. Solar wind double ions beams and the heliospheric current sheet

    Science.gov (United States)

    Hammond, C. M.; Feldman, W. C.; Phillips, J. L.; Goldstein, B. E.; Balogh, A.

    1995-01-01

    Double ion beams are often observed in the solar wind, but little work has been done in relating these beams to structures within the solar wind. Double ion beams are observed as beams of a given ion species and charge state occurring at two different energies. We use the three-dimensional ion plasma instrument on board the Ulysses spacecraft to look for evidence of such beams associated with the heliospheric current sheet. In a subset chosen independently of plasma parameters consisting of 8 of cover 47 crossings of the current sheet made during the inecliptic phase of the Ulysses mission we find that these double ion beams are always present on either side of the current sheet. The double beams are present in both the proton and helium species. The secondary beam typically has a higher helium abundance, which suggests that these beams are formed in the helium-rich corona rather than in interplanetary space. The double beams are not present in the interior of the current sheet. Neither collisions nor effects of plasma beta can account for the disappearance of the double beams inside the current sheet in all eight cases. We postulate that these beams are formed by reconnection occurring near the Sun in the boundary region between the open field lines of the coronal holes and the closed field line region of the heliospheric current sheet. Such a scenario would be consistent with previous X ray measurements which suggect that reconnection is occurring in this region.

  17. Neoclassical Physics for Current Drive in Tokamak Plasmas

    International Nuclear Information System (INIS)

    The Lie transform formalism is applied to charged particle dynamics in tokamak magnetic topologies, in order to build a Fokker-Planck type operator for Coulomb collisions usable for current drive. This approach makes it possible to reduce the problem to three dimensions (two in velocity space, one in real space) while keeping the wealth of phase-space cross-term coupling effects resulting from conservation of the toroidal canonical momentum (axisymmetry). This kinetic approach makes it possible to describe physical phenomena related to the presence of strong pressure gradients in plasmas of an unspecified form, like the bootstrap current which role will be paramount for the future ITER machine. The choice of coordinates and the method used are particularly adapted to the numerical resolution of the drift kinetic equation making it possible to calculate the particle distributions, which may present a strong variation with respect to the Maxwellian under the effect of an electric field (static or produced by a radio-frequency wave). This work, mainly dedicated to plasma physics of tokamaks, was extended to those of space plasmas with a magnetic dipole configuration. (author)

  18. Quasisteady High-Confinement Reversed Shear Plasma with Large Bootstrap Current Fraction under Full Noninductive Current Drive Condition in JT-60U

    International Nuclear Information System (INIS)

    A quasisteady reversed shear plasma with a large bootstrap current fraction (∼80% ) has been obtained for the first time in the JT-60U tokamak. The shrinkage of reversed shear region was suppressed by the bootstrap current peaked at the internal transport barrier (ITB) layer and the ITBs at a large radius were sustained, which, by combination with an H -mode edge pedestal, resulted in a high confinement or 2.2times the H -mode scaling for 6times energy confinement time or 2.7s. Furthermore, a full noninductive current drive was obtained by the bootstrap current and the beam driven current

  19. A thermodynamical analysis of rf current drive with fast electrons

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-08-15

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

  20. A thermodynamical analysis of rf current drive with fast electrons

    Science.gov (United States)

    Bizarro, João P. S.

    2015-08-01

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

  1. A thermodynamical analysis of rf current drive with fast electrons

    International Nuclear Information System (INIS)

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

  2. Current Behaviours and Attitudes Towards Texting While Driving in Australia

    DEFF Research Database (Denmark)

    Adamsen, Jannie Mia; Beasley, Keiran

    2011-01-01

    This paper aims to understand the behaviour of texting and driving among the broader driving public in Australia and uncover whether attitudes are congruent with behaviours. Recent studies have generally been focussing on the behaviours of 18-24 year olds suggesting that the practice is mainly...... confined to people in this age bracket. Findings from an anonymous online survey show that the practice of texting and driving is widespread in Australia and not just confined to the younger demographic. Additionally, evidence suggests smart phone users are more likely to engage in texting while driving...

  3. Measurement of accelerated electron beam current at the Erevan synchrotron

    International Nuclear Information System (INIS)

    A system which ensures high accuracy of accelerated electro n beam current measurement at the synchrotron is described. The expected limits for the frequency characteristic of the measured magnitude, i.e. current of accelerated electron beam, are analyzed. A structure of measurement devices ensuring a necessary frecuency range for measured signals is chosen. A magnetoinduction feedback converter operating in aperiodic mode is taken as a primary beam current monitor. The parameters of the converter with a coincidence amplifier were calculated with a computer. Oscillograms of accelerated electron beam current corresponding to different operational modes of the synchrotron are presented

  4. Current neutralization in ballistic transport of light ion beams

    International Nuclear Information System (INIS)

    Intense light ion beams are being considered as drivers to ignite fusion targets in the Laboratory Microfusion Facility (LMF). Ballistic transport of these beams from the diode to the target is possible only if the beam current is almost completely neutralized by plasma currents. This paper summarizes related work on relativistic electron beam and heavy ion beam propagation and describes a simple simulation model (DYNAPROP) which has been modified to treat light ion beam propagation. DYNAPROP uses an envelope equation to treat beam dynamics and uses rate equations to describe plasma and conductivity generation. The model has been applied both to the high current, 30 MeV Li+3 beams for LMF as well as low current, 1.2 MeV proton beams which are currently being studied on GAMBLE B at the Naval Research Laboratory. The predicted ratio of net currents to beam current is ∼0.1--0.2 for the GAMBLE experiment and ∼0.01 for LMF. The implications of these results for LMF and the GAMBLE experiments art discussed in some detail. The simple resistive model in DYNAPROP has well-known limitations in the 1 torr regime which arise primarily from the neglect of plasma electron transport. Alternative methods for treating the plasma response are discussed

  5. Bootstrap current of fast ions in neutral beam injection heating

    International Nuclear Information System (INIS)

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

  6. Photoinjector beam quality improvement by shaping the wavefront of a drive laser with oblique incidence

    Institute of Scientific and Technical Information of China (English)

    HE Zhi-Gang; WANG Xiao-Hui; JIA Qi-Ka

    2012-01-01

    To increase the quantum efficiency (QE) of a copper photocathode and reduce the thermal emittance of an electron beam,a drive laser with oblique incidence was adopted in a BNL type photocathode rf gun.The disadvantageous effects on the beam quality caused by oblique incidence were analyzed qualitatively.A simple way to solve the problens through wavefront shaping was introduced and the beam quality was improved.

  7. Electron cyclotron heating and current drive in toroidal geometry

    International Nuclear Information System (INIS)

    Work of the Principal Investigator has continued on the development, use and dissemination of numerical tools required in both the planning of electron cyclotron heating experiments and in answering physics questions associated with those experiments. The TORCH code which evolved from the earlier TORAY code has been linked with the BALDUR 11/2 D transport and equilibrium code. This allows us to carry out combined electron cyclotron ray tracing and transport studies for the Compact Ignition Tokamak. Moreover, our concern has not only been with propagation of electron cyclotron radiation into the plasma and the deposition of this radiation there, but also with the excitation and presence of synchrotron radiation and the propagation of that radiation out of the plasma. The ray tracing codes that have been developed for studying ECH heating and current drive, have been generalized and used in our studies to trace the path of synchrotron radiation. This allows us to examine in detail the background as well as the enhanced radiation signals that are detected at the edge of the plasma

  8. Application of Electron Cyclotron Current Drive on ITER

    International Nuclear Information System (INIS)

    The TORAY-GA code has been used to calculate the effectiveness of electron cyclotron waves for applications on the International Tokamak Experimental Reactor (ITER) using the steerable launchers of the reference design. This study focuses on the effect on the electron cyclotron current drive of operation of ITER over a range of toroidal magnetic field BT from 2.35 to 5.3 T. For BT above 4.3 T and for BT near 2.6 T where the second harmonic takes the place of the fundamental, the launchers are satisfactory for addressing the main objectives of ECCD in ITER. Between about 4.3 T and 3.3 T, the top launcher is not usable and the midplane launchers can only be used to deposit heat near the outer part of the plasma. The applications for which the midplane launchers can be used for BT between 3.3 T and 2.6 T depend rather sensitively on the equilibrium and the application

  9. Improved beam current densities at high voltages

    International Nuclear Information System (INIS)

    The performance of ion extractors is analyzed with crude approximations that show improved performance to be possible with the certain modifications. However, additional studies are required to evaluate the beam optics in the presence of the deformed grids

  10. High current precision long pulse electron beam position monitor

    CERN Document Server

    Nelson, S D; Fessenden, T J; Holmes, C

    2000-01-01

    Precision high current long pulse electron beam position monitoring has typically experienced problems with high Q sensors, sensors damped to the point of lack of precision, or sensors that interact substantially with any beam halo thus obscuring the desired signal. As part of the effort to develop a multi-axis electron beam transport system using transverse electromagnetic stripline kicker technology, it is necessary to precisely determine the position and extent of long high energy beams for accurate beam position control (6 - 40 MeV, 1 - 4 kA, 2 μs beam pulse, sub millimeter beam position accuracy.) The kicker positioning system utilizes shot-to-shot adjustments for reduction of relatively slow (< 20 MHz) motion of the beam centroid. The electron beams passing through the diagnostic systems have the potential for large halo effects that tend to corrupt position measurements.

  11. Two-dimensional Fokker-Planck analysis code for RF current drive

    International Nuclear Information System (INIS)

    A two-dimensional Fokker-Planck analysis code has been developed to study applicabilities of current drive to fusion reactors by waves in the ion cyclotron range of frequency. The current drive efficiency can be obtained by the code for various kinds of current drive mechnisms, i.e., Landau damping, transit time magnetic pumping, and their combination. The current profile can also be obtained by coupling the code with a wave equation analysis code. (author)

  12. Advances in modeling of lower hybrid current drive

    Science.gov (United States)

    Peysson, Y.; Decker, J.; Nilsson, E.; Artaud, J.-F.; Ekedahl, A.; Goniche, M.; Hillairet, J.; Ding, B.; Li, M.; Bonoli, P. T.; Shiraiwa, S.; Madi, M.

    2016-04-01

    First principle modeling of the lower hybrid (LH) current drive in tokamak plasmas is a longstanding activity, which is gradually gaining in accuracy thanks to quantitative comparisons with experimental observations. The ability to reproduce simulatenously the plasma current and the non-thermal bremsstrahlung radial profiles in the hard x-ray (HXR) photon energy range represents in this context a significant achievement. Though subject to limitations, ray tracing calculations are commonly used for describing wave propagation in conjunction with Fokker-Planck codes, as it can capture prominent features of the LH wave dynamics in a tokamak plasma-like toroidal refraction. This tool has been validated on several machines when the full absorption of the LH wave requires the transfer of a small fraction of power from the main lobes of the launched power spectrum to a tail at a higher parallel refractive index. Conversely, standard modeling based on toroidal refraction only becomes more challenging when the spectral gap is large, except if other physical mechanisms may dominate to bridge it, like parametric instabilities, as suggested for JET LH discharges (Cesario et al 2004 Phys. Rev. Lett. 92 175002), or fast fluctuations of the launched power spectrum or ‘tail’ LH model, as shown for Tore Supra (Decker et al 2014 Phys. Plasma 21 092504). The applicability of the heuristic ‘tail’ LH model is investigated for a broader range of plasma parameters as compared to the Tore Supra study and with different LH wave characteristics. Discrepancies and agreements between simulations and experiments depending upon the different models used are discussed. The existence of a ‘tail’ in the launched power spectrum significantly improves the agreement between modeling and experiments in plasma conditions for which the spectral gap is large in EAST and Alcator C-Mod tokamaks. For the Alcator C-Mod tokamak, the experimental evolution of the HXR profiles with density suggests

  13. Two 352 MHz push pull linac pairs to generate two drive beams for CLIC multibunch operation

    International Nuclear Information System (INIS)

    The present note describes a drive beam generation scheme for multibunch operation at 1 TeV continuous mode and the luminosity of 1034 cm-2s-1. This rather conventional scheme is essentially based on acceleration with 352 MHz superconducting cavities. Contrary to a previous proposal for single bunch operation, an independent push pull linac pair per drive beam is foreseen mainly for the following reasons. Twice as many drive bunchlets per 352 MHz period halves the required charge per bunchlet. With two trains, the bunchlet deceleration variation inside one train is reduced. A good drive beam to RF efficiencies are obtained through matching of the train energy profile to the decelerating wake pattern in the drive linac. The reduced wake variation makes it feasible to preshape the train energy profile to the required ramp by simple phase shifting of the 352 MHz voltage in the superconducting cavities in conjunction with a small harmonics correction. The layout of the system consists of the 30 GHz accelerating structures, 30 GHz transfer structures, fourth harmonics (1408 MHz) superconducting structures, push pull fundamental (352 MHz) linac pair and switch yards. Emphasis has been put on wall-plug to main beam efficiency and minimum capital cost to the extent possible for the concept chosen. The issues of studies are harmonic synthesis of an optimum acceleration ramp, beam loading compensation for fundamental frequency cavities, acceleration of 22 bunchlets, fourth harmonic cavities, wall plug to main beam efficiency and RF deflectors. The main disadvantage of the scheme seem to be: a) high bunchlet charge of 45 n C. b) overall efficiency of only 10.1%, essentially because of the limited stored RF energy in the 352 MHz structures, which limits the number of drive bunchlet trains per pulse. c) significant amount of RF and cryogenics hardware for complete drive beam generation complex. The main advantage appears to be: a) no long drive beam transport lines, no 180 and

  14. High illumination uniformity scheme with 32 beams configuration for direct-drive inertial confinement fusion

    Science.gov (United States)

    Li, Li; Gu, Chun; Xu, Lixin; Zhou, Shenlei

    2016-04-01

    The self-adapting algorithms are improved to optimize a beam configuration in the direct drive laser fusion system with the solid state lasers. A configuration of 32 laser beams is proposed for achieving a high uniformity illumination, with a root-mean-square deviation at 10-4 level. In our optimization, the parameters such as beam number, beam arrangement, and beam intensity profile are taken into account. The illumination uniformity robustness versus the parameters such as intensity profile deviations, power imbalance, intensity profile noise, the pointing error, and the target position error is also discussed. In this study, the model is assumed a solid-sphere illumination, and refraction effects of incident light on the corona are not considered. Our results may have a potential application in the design of the direct-drive laser fusion of the Shen Guang-II Upgrading facility (SG-II-U, China).

  15. Beam dynamics simulations for linacs driving short-wavelength FELs

    International Nuclear Information System (INIS)

    The fast code HOMDYN has been recently developed, in the framework of the TTF (Tesla test facility) collaboration, in order to study the beam dynamics of linacs delivering high brightness beams as those needed for short wavelength Fel experiments. These linacs are typically driven by radio-frequency photo-injectors, where correlated time dependent space charge effects are of great relevance: these effects cannot be studied by standard beam optics codes (TRACE3D, etc.) and they have been modeled so far by means of multi-particle (Pic or quasistatic) codes requiring heavy cpu time and memory allocations. HOMDYN is able to describe the beam generation at the photo-cathode and the emittance compensation process in the injector even running on a laptop with very modest running rimes (less than a minute). In this paper it is showed how this capability of the code is exploited so to model a whole linac up to the point where the space charge dominated regime is of relevance (200 MeV)

  16. Application of data mining in beam current forecast

    International Nuclear Information System (INIS)

    Data mining technique is briefly introduced in the paper. The comparability of history beam current curves was analyzed first, then a method to forecast the beam current was put forward based on time sequence comparability study, and used in Hefei light source operational data analysis. The result indicates it's useful. (authors)

  17. The current status of the psychoanalytic theory of instinctual drives. I: Drive concept, classification, and development.

    Science.gov (United States)

    Compton, A

    1983-07-01

    The evolution of Freud's theory of instinctual drives, with the accompanying models of a mental apparatus, is remarkable for its tenacious adherence to addressing the fundamental problems of human psychology, here phrased as the problems of body-mind-environment relationships. The concept of instinctual drives continues to be one of the most pervasive concepts of psychoanalysis, weathering considerable attack over the last several decades, although losing some clarity in the process. I have cited and discussed as basic issues of the concept of instinctual drives: the relationship of observational data and theoretical constructs in psychology; whether our construct of drives is or should be or can be purely psychological; the problem of conceptualizing the ontogenetic origin of mind; the issues of the "force-meaning conjunction" and the problem of psychic energy in psychoanalytic constructs; and the relation of our concept of instinctual drives to the concept of instincts in general. It seems that progress with these fundamental issues might be made by utilizing models that are more homologous with present knowledge in related fields than is Freud's reflex arc model of the nervous system, in order to build a better drive construct within the framework of psychoanalysis. The classification of instinctual drives remains a problem. Clinically, aggression seems to be a factor in conflict, very much like sexuality. Despite widespread acceptance of the idea of aggression as simply parallel to sexuality in all respects, there are major discrepancies. Perhaps aggression cannot be viewed as a drive after all; perhaps our drive construct needs to be modified to accommodate aggression. Certainly, controversy in this area has interfered with the production of good clinical studies which could begin to increase our understanding of aggression and its place in the human personality. The psychoanalytic theory of drive development has probably undergone less change in the last

  18. Fast Beam Current Change Monitor for the LHC

    CERN Document Server

    Kral, Jan

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

  19. Low Current, Long Beam Pulse with SLED

    International Nuclear Information System (INIS)

    The 3 km long linac at the Stanford Linear Accelerator Center (SLAC) is used for fixed target experiments such as E-155, with energies up to 50 GeV. The SLAC Energy Development (SLED) system increase the maximum no-load energy by a factor of 1.6, but it also causes a varying beam energy curve. To provide a long pulse or bunch train for the experiment the energy profile has to be flat. Besides more sophisticated methods such as varying the phase of two klystrons feeding one structure section as proposed in the NLC design, we describe the method used for E-155 in spring of 1997. The desired low charged beam didn't have any significant beam loading, but by inserting a 1800 phase notch during the SLED pulse, a beam pulse of up to 500 ns was achieved. The energy range without compensation would have been 15%, while with compensation the energy spread was reduced to about 0.15%. The phase notch was achieved by triggering a pair of two additional 180d0 phase switches about half a structure fill-time after the SLED pulse was triggered. Simulations are compared with the experimental result

  20. High-current runaway electron beam in a tokamak plasma

    International Nuclear Information System (INIS)

    An equilibrium of toroidal plasma with a large electron-beam current has been realized using the runaway effect in a tokamak. Reproducible runaway-mode discharges are obtained with pure hydrogen gas by the help of intense titanium flashing which results in a low electron density. The beam current is estimated to be more than a half of the total toroidal current. The equilibrium of this discharge is maintained by a strong vertical field because the beam pressure gives rise to an additional increase in Shafranov Λ. The beam pressure is estimated to be more than 80% of the total pressure. The kinetic energy and the spatial distributions of beam electrons are studied by seeing X-ray emission from a tungsten wire inserted into the plasma. The increase of Shafranov Λ due to beam pressure is enhanced by puffing gas into the discharge. (author)

  1. Impact of Toroidal Effect on Lower Hybrid Current Drive in Tokamak

    Institute of Scientific and Technical Information of China (English)

    Jiao Yiming; Long Yongxing; Dong Jiaqi; Gao Qingdi

    2005-01-01

    The main topics concerning lower hybrid wave heating (LHH) and lower hybrid current drive (LHCD) in tokamak systems are presented. The inherent properties of tokamak the other hand, induce a consumption of wave energy by the trapped electrons, which reduce the current drive efficiency. The methods for the enhancement of the current drive efficiency may be derived from detailed analyses by drawing upon the ray tracing technology on toroidal geometry and the Fokker-Planck theory on velocity space.

  2. High-current negative-ion beam transport

    International Nuclear Information System (INIS)

    The requirements for transporting high-current, negative-ion beams are presented with particular emphasis on applications involving negative-hydrogen-ion beams. In addition to the usual matching and steering problems, particular attention must be paid to beam emittance growth in the transport system. Depending on the application, a number of approaches have been developed using both magnetic and electric lenses. I discuss the design considerations for transporting and matching these beams to radiofrequency quadrupole accelerators, and present a survey of the various types of beamlines now used for negative-ion beams

  3. Heating, current drive and energetic particles studies on JET in preparation of ITER operation

    International Nuclear Information System (INIS)

    This paper summarizes the recent work on JET in the three areas of heating, current drive and energetic particles. The achievements have extended the possibilities of JET, have a direct connection to ITER operation and provide new and interesting physics. Toroidal rotation profiles of plasmas heated far off axis with little or no refueling or momentum input are hollow with only small differences on whether the power deposition is located on the low field side or on the high field side. With LH current drive the magnetic shear was varied from slightly positive to negative. The improved coupling (through the use of plasma shaping and CD4) allowed up to 3.4 MW of PLH in ITB plasmas with more than 15MW of combined NBI and ICRF heating. The q profile with negative magnetic shear and the ITB could be maintained for the duration of the high heating pulse (8s). Fast ions have been produced in JET with ICRF to simulate alpha particles: by using third harmonic 4He heating, beam injected 4He at 120 kV were accelerated to energies above 2 MeV, taking advantage of the unique capability of JET to use NBI with 4He and to confine MeV class ions. ICRF heating was used to replicate the dynamics of alpha heating and the control of an equivalent Q=10 'burn' was simulated. (author)

  4. Studies of Cs3Sb cathodes for the CLIC drive beam photo injector option

    CERN Document Server

    Martini, Irene; Doebert, Steffen; Fedosseev, Valentine; Hessler, Christoph; Martyanov, Mikhail

    2013-01-01

    Within the CLIC (Compact Linear Collider) project, feasibility studies of a photo injector option for the drive beam as an alternative to its baseline design using a thermionic electron gun are on-going. This R&D program covers both the laser and the photocathode side. Whereas the available laser pulse energy in ultra-violet (UV) is currently limited by the optical defects in the 4thharmonics frequency conversion crystal induced by the0.14 ms long pulse trains, recent measurements of Cs3Sbphotocathodes sensitive to green light showed their potential to overcome this limitation. Moreover, using visible laser beams leads to better stability of produced electron bunches and one can take advantages of the availability of higher quality optics. The studied Cs3Sbphotocathodes have been produced in the CERN photo emission laboratory using the co-deposition technique and tested in a DC gun set-up. The analysis of data acquired during the cathode production process will be presented in this paper, as well as the r...

  5. Design and development of DCCT for measurement of beam current

    International Nuclear Information System (INIS)

    Charged Particle beams in accelerators need measurement of beam current during operations and diagnostics. The beam passes through a resonant cavity that is excited at a fixed resonant frequency and is maintained at a vacuum level as high as 10E-8 Ton. Non-intrusive method is needed for beam current measurement. DCCT is a non-intrusive, accurate and stable device that is widely used for measurement of the beam intensity in particle accelerators. DCCT is based on principle of flux gate magnetometers. It consists of magnetic modulator, magnetizing coils, sense coils, back end and front end electronics. A prototype DCCT for vacuum chamber of 24 mm nominal inner diameter is designed and developed at CnID. During laboratory experiments beam current is simulated by passing DC current generated by stable current source along the axis of the DCCT. In absence of beam current sense coils senses zero voltage. Even harmonics are generated at the output winding when DC current is passed and the magnitude of the 2nd harmonic gives the corresponding value of the beam current. The prototype DCCT is designed for 0.5 mA to 10 mA range with resolution better than 0.1 mA. This paper describes the magnetic, electronics and mechanical design of the prototype DCCT which is optimized for amplitude and frequency of magnetizing current. The dependence of the amplitude and frequency of the magnetizing current on the second harmonic is discussed in detail. Shielding to external noise is provided with help of high permeability soft magnetic material. A compensation core with coil is used to determine the direction/charge of the beam. The current in this coil is tuned to reduce the 2nd harmonics generated due to beam current, back to zero. The value of this current gives magnitude of the beam current and its polarity gives information on direction/charge of the beam. Front and back end electronics designed for prototype DCCT is also discussed. It is planned to deploy the developed DCCT in Linac

  6. Computer simulation of high current uranium beams for the injection beam line of the UNILAC

    International Nuclear Information System (INIS)

    In an attempt to generate an ion beam with high current and high brightness for the design ion, the computer code KOBRA3-INP has been used to evaluate the extraction system, the DC post-acceleration system as well as the quadrupole transport beam line, and to study the behavior of the ion beam in the combined system. (orig.)

  7. Current ramp-up experiments in full current drive plasmas on TRIAM-1M

    International Nuclear Information System (INIS)

    Four types of plasma current ramp-up experiments were executed on TRIAM-1M in full lower hybrid current drive plasmas (LHCD: 8.2GHz, up to 0.4 MW, 8 x 2 grill antenna); 1) the current start up by the combination between electron cyclotron resonance heating (ECH: 170GHz, up to 0.2 MW, O-mode launching) and LHCD at the density of ∼2x1019m-3 at Bt=6.7T, 2) the tail heating by the additional LHCD, 3) the bulk heating by ECH, 4) the spontaneous ramp up by the transition to enhanced current drive (ECD) mode. The time evolutions of plasma current during four types of ramp-up phase were investigated and an exponential type and a tangent-hyperbolic one were observed. The time evolutions of plasma current during the tail and the bulk heating show the exponential type except the tail heating with high nparallel and it has a tangent-hyperbolic one during the ECD mode and the current start-up. A simple model with two different time constants, which are a time defined by L/R, τL/R, and a time caused by change of the effective refractive index along the magnetic field, τ, is proposed to explain two types of the time evolution of the plasma current. The estimated τL/R is consistent with the calculated one from the plasma parameter. It is found that τ are less than τL/R in the cases of the tail and the bulk heating, and comparable in the cases of the ECD mode, and more than τL/R in the cases of the plasma start-up. This indicates that the value of the effective refractive index along the magnetic field, parallel>, develops during the ECD mode and the current start-up. The value of τ depends on the RF power. The estimated is close to the expected up-shifted nparallel due to the toroidal effect and the magnetic shear. (author)

  8. Propagation and scattering in Lower Hybrid Current Drive (LHCD)

    International Nuclear Information System (INIS)

    Full text of publication follows. The propagation and scattering of the 5 GHz RF waves planned for driving and controlling the plasma current in stage 2 of ITER is analyzed with theory, simulations and data from Tore Supra. The internal RF wavenumber spectrum is determined by a combination of elements including the (1) the azimuthal spectrum launched by the antenna, (2) coupling of the radial and azimuthal oscillations of the ray trajectories described the ray Hamiltonian with the radial and the poloidal variation of plasma and scattering from the drift wave turbulence (ref. 1, 2). The scattering of the RF waves from the drift wave turbulence in the plasma is described through a Fokker-Planck equation for the probability density of the rays. The new 4D ray kinetic equation has (1) an edge source from the antenna, (2) a core sink from the electron resonances, and (3) a global scattering rate tensor Dij(k,r,t) derived from the ambient plasma turbulence. The tensor reduces to a parallel and cross-field component with the cross-field component describing side-scatter of the RF waves. The solutions give a spectral distribution for the parallel index of refraction from the antenna to the region of three times the core electron thermal velocity. Strong absorption of the rays occurs where the plateau in the fast electron distribution joins the steeply increasing slope of the thermal electron phase space density (ref. 3). Solutions of the ray kinetic equation with the source, sink and scattering provide the filling of the spectral gap and the efficiency of the LHCD system. The ETG turbulence is modified by the temperature anisotropies and the sharp radial gradients of the LHCD electron distribution function (ref. 3). In the presence of the ETG turbulence projections of the partial differential equations to low-order transport models are derived with dynamical feed-forward/ feedback loops following L-H-ELM modeling (ref. 4). The low-order models may be used with feedback

  9. The development of beam current monitors in the APS

    International Nuclear Information System (INIS)

    The Advanced Photon Source (APS) is a third-generation 7-GeV synchrotron radiation source. The precision measurement of beam current is a challenging task in high energy accelerators, such as the APS, with a wide range of beam parameters and complicated noise, radiation, and thermal environments. The beam pulses in the APS injector and storage ring have charge ranging from 50pC to 25nC with pulse durations varying from 30ps to 30ns. A total of nine non- intercepting beam current monitors have been installed in the APS facility (excluding those in the linac) for general current measurement. In addition, several independent current monitors with specially designed redundant interlock electronics are installed for personnel safety and machine protection. This paper documents the design and development of current monitors in the APS,. discusses the commissioning experience in the past year, and presents the results of recent operations

  10. Electrical measurement techniques for pulsed high current electron beams

    International Nuclear Information System (INIS)

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

  11. Enhancing the accelerated beam current in the booster synchrotron by optimizing the transport line beam propagation

    Indian Academy of Sciences (India)

    Saini R S; Tyagi Y; Ghodke A D; Puntambekar T A

    2016-04-01

    In this paper, we present the results of transverse beam emittance and twiss parameter measurement of an electron beam, delivered by a 20 MeV microtron which is used as a pre-injector system for a booster synchrotron in the Indus Accelerator Facility at RRCAT Indore. Based on these measured beam parameters, beam optics of a transport line was optimized and its results are alsodiscussed in this paper. This beam transport line is used to transport the electron beam from the 20MeV microtron to the booster synchrotron. The booster synchrotron works as a main injector for Indus-1 and Indus-2 synchrotron radiation facilities. To optimize the beam optics of a transport linefor proper beam transmission through the line as well as to match the beam twiss parameters at the beam injection point of another accelerator, it is necessary to know the transverse beam emittance and twiss parameters of the beam coming from the first one. A MATLAB-based GUI program has been developed to calculate the beam emittance and twiss parameters, using quadrupole scanmethod. The measured parameters have been used for beam transport line optimization and twiss parameters matching at booster injection point. After this optimization, an enhancement of ∼50% beam current has been observed in the booster synchrotron.

  12. A Gas-Jet Profile Monitor for the CLIC Drive Beam

    CERN Document Server

    Jeff, A; Lefevre, T; Tzoganis, V; Welsch, C P

    2013-01-01

    The Compact Linear Collider (CLIC) will use a novel acceleration scheme in which energy extracted from a very intense beam of relatively low-energy electrons (the Drive Beam) is used to accelerate a lower intensity Main Beam to very high energy. The high intensity of the Drive Beam, with pulses of more than 1015 electrons, poses a challenge for conventional profile measurements such as wire scanners. Thus, new non-invasive profile measurements are being investigated. Profile monitors using gas ionisation or fluorescence have been used at a number of accelerators. Typically, extra gas must be injected at the monitor and the rise in pressure spreads for some distance down the beam pipe. In contrast, a gas jet can be fired across the beam into a receiving chamber, with little gas escaping into the rest of the beam pipe. In addition, a gas jet shaped into a thin plane can be used like a screen on which the beam crosssectionis imaged. In this paper we present some arrangements for the generation of such a jet. In ...

  13. Low Starting Electron Beam Current in Degenerate Band Edge Oscillators

    CERN Document Server

    Othman, Mohamed A K; Figotin, Alexander; Capolino, Filippo

    2016-01-01

    We propose a new principle of operation in vacuum electron-beam-based oscillators that leads to a low beam current for starting oscillations. The principle is based on super synchronous operation of an electron beam interacting with four degenerate electromagnetic modes in a slow-wave structure (SWS). The four mode super synchronous regime is associated with a very special degeneracy condition in the dispersion diagram of a cold periodic SWS called degenerate band edge (DBE). This regime features a giant group delay in the finitelength SWS and low starting-oscillation beam current. The starting beam current is at least an order of magnitude smaller compared to a conventional backward wave oscillator (BWO) of the same length. As a representative example we consider a SWS conceived by a periodically-loaded metallic waveguide supporting a DBE, and investigate starting-oscillation conditions using Pierce theory generalized to coupled transmission lines (CTL). The proposed super synchronism regime can be straightf...

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

    Science.gov (United States)

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

    2016-02-01

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

  15. RADLAC II high current electron beam propagation experiment

    International Nuclear Information System (INIS)

    The resistive hose instability of an electron beam was observed to be convective in recent RADLAC II experiments for higher current shots. The effects of air scattering for these shots were minimal. These experiments and theory suggest low-frequency hose motion which does not appear convective may be due to rapid expansion and subsequent drifting of the beam nose

  16. Optimal condition for oscillating field current drive in a bootstrapped tokamak

    International Nuclear Information System (INIS)

    A simple physical form of the optimal condition for oscillating field current drive (OFCD) in a bootstrapped tokamak is given. The results of the analysis suggest that the required OFCD driving frequency can be reduced in a bootstrapped tokamak directly in proportion to the reduction in the OFCD fraction of the total toroidal current, while the total required poloidal magnetic flux content is independent of the OFCD driving frequency. (author)

  17. Brushless DC motor Drive during Speed regulation with Current Controller

    OpenAIRE

    Bhikshalu Manchala; T.Amar Kiran

    2015-01-01

    Brushless DC Motor (BLDC) is one of the best electrical drives that have increasing popularity, due to their high efficiency, reliability, good dynamic response and very low maintenance. Due to the increasing demand for compact & reliable motors and the evolution of low cost power semiconductor switches and permanent magnet (PM) materials, brushless DC motors become popular in every application from home appliances to aerospace industry. The conventional techniques for controlling...

  18. Optimization of Driving Based on Currently Measured Data

    Czech Academy of Sciences Publication Activity Database

    Nagy, Ivan; Suzdaleva, Evgenia; Mlynářová, Tereza

    Hague: IEEE, 2013, s. 2088-2093. ISBN 978-1-4799-2914-6. [16th International IEEE Conference on Intelligent Transportation Systems (ITSC 2013). The Hague (NL), 06.10.2013-09.10.2013] R&D Projects: GA TA ČR TA01030123 Institutional support: RVO:67985556 Keywords : fuel consumption optimization * eco-driving * adaptive control Subject RIV: BC - Control Systems Theory http://library.utia.cas.cz/separaty/2013/AS/nagy-0397318.pdf

  19. An Improved Variable-Frequency Drive Based on Current Tracking

    Directory of Open Access Journals (Sweden)

    Zhiwei He

    2013-11-01

    Full Text Available Variable frequency devices are widely used in many power systems. A current tracking based VFD is proposed in this paper. The output current is firstly fed back and compared with a standard sine wave, the difference of them is then used for a PI regulator to control the PWM signal, so as to change the output current accordingly to make it approach the standard sine wave. Simulation and experiments results show that the current tracking VFD not only has a fast dynamic response, high current tracking precision, current limiting ability, but also has small distortion of the output sine wave current and low loss of the motor.    

  20. Electron-Bernstein-wave current drive in an overdense plasma at the Wendelstein 7-AS stellarator

    International Nuclear Information System (INIS)

    Electron-Bernstein-wave (EBW) current drive in an overdense plasma was demonstrated at the Wendelstein 7-AS stellarator for the first time. The EBWs were generated by O-X-B mode conversion. The relatively high current drive efficiency was consistent with theoretical predictions. The experiments provided first investigations of EBW phase space interaction for wave refractive indices much larger than unity

  1. Determination of passive synchrotron radiation current drive efficiency in tokamaks with fish-scale first wall

    International Nuclear Information System (INIS)

    Current drive efficiency generated by asymmetric synchrotron radiation in tokamaks is investigated. It is shown that experimental measurements of the differential first wall reflectivity determining the asymmetric cyclotron radiation and the related current drive can be envisaged in existing tokamaks using conventional measurements of radiation temperature. (author)

  2. Development of an external Faraday cup for beam current measurements

    International Nuclear Information System (INIS)

    In general, beam current measurements are very important for many kinds of experiments using highly energetic particle beams at accelerators, such as cyclotrons, linacs, etc. The Faraday cup is known to be one of the most popular beam current measurement tools. We developed an external Faraday cup to measure the beam current at a dedicated beam line for low-flux experiments installed at the MC-50 cyclotron of Korea Institute of Radiological and Medical Sciences (KIRAMS). It was designed for external beam current measurements and is composed of a vacuum chamber, an entrance window, a collimator, a electrostatic suppressor ring, and a cup. The window is made of 75-um-thick Kapton film, and the diameter of the collimator is 10 mm or 20 mm. The ring and the cup has 5-cm inner diameters, and the thickness of the bottom of the cup is 2 cm, which is enough to absorb the total proton energy up to 45 MeV. Using this external Faraday cup, we measured the beam current from the cyclotron, and we compared measured flux to the results from film dosimetry using GAF films.

  3. Dynamics of a high-current relativistic electron beam

    International Nuclear Information System (INIS)

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

  4. ADAPTIVE CONTROL OF FLEXIBLE BEAM WITH UNKNOWN DEAD-ZONE IN THE DRIVING MOTOR

    Institute of Scientific and Technical Information of China (English)

    Wang Xingsong; Hong Henry; Su Chunyi

    2004-01-01

    Adaptive control of a flexible beam system preceded by an unknown dead-zone in the driving motor is investigated in state space form. By introducing an important lemma for simplifying error equation between the flexible beam model and the matching reference model, a robust adaptive control scheme is developed by involving the dead-zone inverse terms. The new adaptive control law ensures global stability of the entire system and achieves desired tracking precision even when the slopes of the dead-zone are not equal. Simulations performed on a typical flexible beam system illustrate and clarify the validity of this approach.

  5. Collective effects and experimental verification of the CLIC drive beam and decelerator

    OpenAIRE

    2014-01-01

    The Compact Linear Collider (CLIC) is a potential next-generation particle collider, in which electrons and positrons collide at a center-of-mass energy of up to 3 TeV. In order to reach a high accelerating gradient and reduce the length of the machine, CLIC uses a novel two-beam scheme. Here, the acceleration energy for the main beam is provided by energy extraction from a secondary electron drive beam, by the use of Power Extraction and Transfer Structures (PETS). This Ph.D. thesis descr...

  6. Production of high-efficiency microsecond heavy-current beams

    International Nuclear Information System (INIS)

    The comparative analysis of various constructions of diodes with magnetic insulation is reported. It is shown that the diode current leakage decrease results in increase of pulse duration of relativistic electron beam and diode efficiency. A ring high quality electron beam of 0.6 MeV energy, current - 3-4 kA, duration - 2.5 μs and ring width 0.8 - 1 mm is obtained

  7. Integrated modelling of steady-state scenarios and heating and current drive mixes for ITER

    International Nuclear Information System (INIS)

    current drive including parallel momentum conservation effects and for neutral beam current drive with finite orbit and magnetic pitch effects.

  8. Beam loading compensation of traveling wave linacs through the time dependence of the rf drive

    International Nuclear Information System (INIS)

    Beam loading in traveling-wave linear accelerating structures leads to unacceptable spread of particle energies across an extended train of bunched particles due to beam-induced field and dispersion. Methods for modulating the rf power driving linacs are effective at reducing energy spread, but for general linacs do not have a clear analytic foundation. We report here methods for calculating how to modulate the rf drive in arbitrarily nonuniform traveling-wave linacs within the convective-transport (power-diffusion) model that results in no additional energy spread due to beam loading (but not dispersion). Varying group velocity, loss factor, and cell quality factor within a structure, and nonzero particle velocity, are handled.

  9. Recent progress in JET on heating and current drive studies in view of ITER

    International Nuclear Information System (INIS)

    Full text: This paper summarizes recent results obtained on JET for optimizing heating and current drive systems, in view of ITER. Fast T ions, injected during off-axis beam heating show anomalous transport to the plasma centre for discharges with ITER relevant q95 ∼ 3. This is not the case for discharges with high q95 ∼ 8. Several possible reasons for this anomaly have been investigated, but so far the results are not explained. Similar effects have been seen on other tokamaks. The results of this study could show to be of importance to improve predictions for the off-axis NBI current drive for ITER. Fast fusion born alpha particles in ITER could induce sawteeth with long periods, which in turn could create seed islands large enough to trigger NTMs. Recent JET experiments demonstrated that fast ion induced long sawteeth can be destabilised with ICCD applied close to the q=1 surface. This driven current significantly increases the shear at the q=1 surface (as confirmed by simulations with the SELFO code) and leads to sawtooth destabilisation. This study shows also that any method capable of driving a current of sufficient magnitude around the q=1 surface would be useful for ITER. Polychromatic ICRF heating should allow better ion heating on ITER compared to monochromatic heating. This has been tested in JET using 3He and H minority heating in D plasmas with different frequencies simultaneously excited on the 4 JET ICRF antennas. Fast ion tail temperature and energy content are found to be lower with polychromatic heating; smaller-amplitude and shorter-period sawteeth, and higher ion to electron temperature ratios have been observed. Inverted heating scenarios are one of the few options for ICRH heating during the hydrogen phase of ITER. Exploration of such scenarios at JET showed the importance of small amounts (1-2%) of C impurity ions, as their presence prevents any D minority heating. Results are confirmed with TOMCAT and CYRANO simulations. Increasing the

  10. Large Dynamic Range Beam Profile Measurements with Low Current Electron Beams

    International Nuclear Information System (INIS)

    Large dynamic range [Peak/Noise > 105] beam profile measurements are routinely performed in the Hall-B beamline at Jefferson Lab. These measurements are made with a 1 to 10nA electron beam current with energies between 1 to 6 GeV. The electron beam scatters off of a thin [25 mu-m] W or Fe wire and the scattered particle/shower is detected via scintillation or Cerenkov light several meters downstream of the wire. This light is converted to an electrical pulse via photomultiplier tubes [PMT]. The PMT readout and wire motion are controlled and synchronized by VME electronics. This report describes results on increasing the dynamic range by using multiple wires of varying diameters. Profile measurements with this large dynamic range can be of use for machines with very large beam currents (ERL) where any FR-actional beam loss represents a significant amount of beam power [1,2

  11. Observation of Lower-Hybrid Current Drive at High Densities in the Alcator C Tokamak

    Science.gov (United States)

    Porkolab, M.; Schuss, J. J.; Lloyd, B.; Takase, Y.; Texter, S.; Bonoli, P.; Fiore, C.; Gandy, R.; Gwinn, D.; Lipschultz, B.; Marmar, E.; Pappas, D.; Parker, R.; Pribyl, P.

    1984-07-01

    A quasi-steady-state lower-hybrid current-drive operation is demonstrated in the Alcator C tokamak at densities up to n―e~=1×1014 cm-3. The current-drive efficiency is measured experimentally over a wide range of densities and magnetic fields. The radial distribution of high-energy x rays indicates that the current-carrying electrons peak near the plasma axis.

  12. ANALYSIS OF EFFECTS OF VECTOR CONTROL ON TOTAL CURRENT HARMONIC DISTORTION OF ADJUSTABLE SPEED AC DRIVE

    Directory of Open Access Journals (Sweden)

    KARTIK TAMVADA

    2012-04-01

    Full Text Available Adjustable speed drive (ASD is becoming a significant load component for power distribution. It involves the use of an Induction motor (IM. This paper involves modeling and control of an Induction motor andinvestigates its effects on the total current harmonic distortion of the adjustable speed ac drives. The simulation was carried out with the aid of the Simulink toolbox available in Matlab. It is seen that with Vector control the THDi of the drive reduces considerably.

  13. ANALYSIS OF EFFECTS OF VECTOR CONTROL ON TOTAL CURRENT HARMONIC DISTORTION OF ADJUSTABLE SPEED AC DRIVE

    OpenAIRE

    KARTIK TAMVADA; R.KAMESWARA RAO

    2012-01-01

    Adjustable speed drive (ASD) is becoming a significant load component for power distribution. It involves the use of an Induction motor (IM). This paper involves modeling and control of an Induction motor andinvestigates its effects on the total current harmonic distortion of the adjustable speed ac drives. The simulation was carried out with the aid of the Simulink toolbox available in Matlab. It is seen that with Vector control the THDi of the drive reduces considerably.

  14. Beam centroid motion estimate for a high current LIA

    International Nuclear Information System (INIS)

    A high current linear induction accelerator now is being constructed in Institute of Fluid Physics. It consists of 18 blocks, totally 72 induction accelerating cells, and 18 connection cells with ports for beam diagnostic hardware and vacuum pump. The goal of the facility is to obtain high quality, high current pulse electron beams. In order to reduce corkscrew motion caused by energy spread and misalignment of a focusing system some measures to control the transverse motion of beam centroid must be taken. At first magnetic alignment is performed by using pulsed-wire technique very carefully, then the tilt errors is corrected by a pair of steering coils, which are located inside each cell, after that based on the alignment data a simple estimate of the beam centroid motion has been done by transfer matrix algorithm. In this paper, the calculated and analysis results are presented

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

    International Nuclear Information System (INIS)

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

  16. Current drive by EC and LH waves in Tore Supra for steady-state reactor studies

    International Nuclear Information System (INIS)

    A long term ECRH program in TORE SUPRA for current drive researches is proposed. The aim of the program is twofold, namely, optimization of the rf driven current in TS by an appropriate combination of LH and EC waves and the search of current drive scenarii of relevance for the steady-state reactor. It is shown that under favourable conditions, steady-state operation can be envisioned by rf current drive with a marginally acceptable efficiency. Experimental results on selective wave absorption at down shifted frequency obtained in PLT and on current drive by EC and LH wave in WT-2 and JFT-2M are given besides the studies presented on Tore Supra

  17. Determination of the Electron Cyclotron Current Drive Profile

    International Nuclear Information System (INIS)

    Evaluation of the profile of non-inductive current density driven by absorption of electron cyclotron waves (ECCD) using time evolution of the poloidal flux indicated a broader profile than predicted by theory. To determine the nature of this broadening, a 1-1/2 D transport calculation of current density evolution was used to generate the signals which the DIII-D motional Stark effect (MSE) diagnostic would measure in the event that the current density evolution followed the neoclassical Ohm's law with the theoretical ECCD profile. Comparison with the measured MSE data indicates the experimental data is consistent with the ECCD profile predicted by theory. The simulations yield a lower limit on the magnitude of the ECCD which is at or above the value found in Fokker-Planck calculations of the ECCD including quasilinear and parallel electric field effects

  18. Some Properties of Current Source Inverter Fed Induction Motor Drive

    Czech Academy of Sciences Publication Activity Database

    Lettl, Jiří; Frackiewicz, Z.

    Szczecin: Technical University of Szczecin, 2001, s. 657-660. ISBN 83-88764-70-5. [International Conference UEES 01 /5./. Miedzyzdroje (PL), 05.09.2001-08.09.2001] Institutional research plan: CEZ:AV0Z2057903 Keywords : induction motor * current source inverter * torque angle control Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  19. Current drive and profile control in low aspect ratio tokamaks

    International Nuclear Information System (INIS)

    The key to the theoretically predicted high performance of a low aspect ratio tokamak (LAT) is its ability to operate at very large plasma current*Ip. The plasma current at low aspect ratios follows the approximate formula: Ip ∼ (5a2Bt/Rqψ) [(1 + κ2)/2] [A/(A - 1)] where A quadruple-bond R/a which was derived from equilibrium studies. For constant qψ and Bt, Ip can increase by an order of magnitude over the case of tokamaks with A approx-gt 2.5. The large current results in a significantly enhanced βt (quadruple-bond βNIp/aBt) possibly of order unity. It also compensates for the reduction in A to maintain the same confinement performance assuming the confinement time τ follows the generic form ∼ HIpP-1/2R3/2κ1/2. The initiation and maintenance of such a large current is therefore a key issue for LATs

  20. Magnetoinduction sensor of beam current with magnetic noise screening

    International Nuclear Information System (INIS)

    A description is given of a magnetoinduction sensor of beam current in a synchrotron, the latter being a booster of the VEhPP-4 electron-positron complex. The sensor operates under conditions of heavy background noise induced by the synchrotron pulsed magnetic fields. The means reducing the noise level in the sensor are considered. The most efficient screen protecting against pulsed fields is one made of conducting materials where the field is reduced at the expense of induced currents passing in a skin-layer. The screen has an azimuthal slit, which results in the beam vortex field penetration to the sensor without reduction. The noise field is reduced due to the conducting walls and deep slit. Application of the means deseribed allowed to measure low (of the order of 100 mcA) synchrotron beam currents

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

    Science.gov (United States)

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

    2012-01-01

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

  2. Theoretical studies of lower hybrid current drive in the Alcator C tokamak

    International Nuclear Information System (INIS)

    Theoretical studies of lower hybrid current drive in the Alcator C tokamak using a simulation model is presented, the model incorporates a 1-D radial transport code to solve for the time evolution of the bulk plasma quantities

  3. Fast wave current drive modeling using the combined RANT3D and PICES codes

    International Nuclear Information System (INIS)

    Two numerical codes are combined to give a theoretical estimate of the current drive and direct electron heating by fast waves launched from phased antenna arrays on the DIII-D tokamak. Results are compared with experiment

  4. Radio-frequency wave trajectories for current drive in tokamak reactors

    International Nuclear Information System (INIS)

    Detailed ray tracing calculations were carried out for three modes of waveguide-launched radio-frequency waves for tokamak reactor parameters to evaluate their applicability for steady state current drive. The merits and demerits of each mode are discussed

  5. Isotopic effect in experiments on lower hybrid current drive in the FT-2 tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Lashkul, S. I., E-mail: Serguey.lashkul@mail.ioffe.ru; Altukhov, A. B.; Gurchenko, A. D., E-mail: aleksey.gurchenko@mail.ioffe.ru; Gusakov, E. Z.; D’yachenko, V. V.; Esipov, L. A.; Irzak, M. A., E-mail: irzak@mail.ioffe.ru; Kantor, M. Yu.; Kouprienko, D. V.; Saveliev, A. N.; Stepanov, A. Yu. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Shatalin, S. V. [St. Petersburg State Technical University (Russian Federation)

    2015-12-15

    To analyze factors influencing the limiting value of the plasma density at which lower hybrid (LH) current drive terminates, the isotopic factor (the difference in the LH resonance densities in hydrogen and deuterium plasmas) was used for the first time in experiments carried out at the FT-2 tokamak. It is experimentally found that the efficiency of LH current drive in deuterium plasma is appreciably higher than that in hydrogen plasma. The significant role of the parametric decay of the LH pumping wave, which hampers the use of the LH range of RF waves for current drive at high plasma densities, is confirmed. It is demonstrated that the parameters characterizing LH current drive agree well with the earlier results obtained at large tokamaks.

  6. Radio-frequency wave trajectories for current drive in tokamak reactors

    Energy Technology Data Exchange (ETDEWEB)

    Wong, K.L.; Ono, M.

    1982-12-01

    Detailed ray tracing calculations were carried out for three modes of waveguide-launched radio-frequency waves for tokamak reactor parameters to evaluate their applicability for steady state current drive. The merits and demerits of each mode are discussed.

  7. Coupling of α-channeling to |k∥| upshift in lower hybrid current drive

    Energy Technology Data Exchange (ETDEWEB)

    Ochs, I. E. [Harvard University, Cambridge, MA (United States). Department of Physics.; Bertelli, N. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Fisch, N. J. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

    2014-08-26

    Although lower hybrid waves have been shown to be effective in driving plasma current in present-day tokamaks, they are predicted to strongly interact with the energetic α particles born from fusion reactions in eventual tokamak reactors.

  8. Langmuir probe study in the nonresonant current drive regime of helicon discharge

    Indian Academy of Sciences (India)

    Manash Kumar Paul; Dhiraj Bora

    2008-07-01

    Characterization of the current drive regime is done for helicon wave-generated plasma in a torus, at a very high operating frequency. A radiofrequency-compensated Langmuir probe is designed and used for the measurement of plasma parameters along with the electron energy distributions in radial scans of the plasma. The electron energy distribution patterns obtained in the operational regime suggest that Landau damping cannot be responsible for the efficient helicon discharge in the present study. A typical peaked radial density profile, high plasma temperature and absence of an appreciable amount of energetic electrons for resonant wave–particle interactions, suggest that the chosen operational regime is suitable for the study of nonresonant current drive by helicon wave. Successful and significant current drive achieved in our device clearly demonstrates the capability of nonresonant current drive by helicon waves in the present operational regime.

  9. Quadrupole betatron accelerator for high current ion beams

    International Nuclear Information System (INIS)

    Properties of a strong non-neutral ion ring in a quadrupole betatron field are investigated. Superimposed on the axial betatron field, it is shown that the quadrupole field is necessary for the stability of the orbits where the self-fields of the ion ring are not negligible. A closed algebraic expression for the ion limiting current is obtained in terms of the quadarupole field intensity, the channel radius, the transverse temperature of ion beam, and the strength of betatron field. According to the theoretical calculation, high energy ion beam with its current order of one kiloampere can easily be attainable

  10. A relativistic model of electron cyclotron current drive efficiency in tokamak plasmas

    OpenAIRE

    Lin-Liu Y.R.; Hu Y.J.; Hu Y.M.

    2012-01-01

    A fully relativistic model of electron cyclotron current drive (ECCD) efficiency based on the adjoint function techniques is considered. Numerical calculations of the current drive efficiency in a tokamak by using the variational approach are performed. A fully relativistic extension of the variational principle with the modified basis functions for the Spitzer function with momentum conservation in the electron-electron collision is described in general tokamak geometry. The model developed ...

  11. DPSS Laser Beam Quality Optimization Through Pump Current Tuning

    Energy Technology Data Exchange (ETDEWEB)

    Omohundro, Rob; /Newport Spectra-Physics, Santa Clara; Callen, Alice; /SLAC; Sukuta, Sydney; /San Jose City Coll.

    2012-03-30

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

  12. Fast-wave current-drive efficiency calculations for JET A2-antennas

    International Nuclear Information System (INIS)

    Fast-wave transit-time magnetic-pumping (TTMP) current drive efficiency calculating using ray tracing techniques are presented using A2-antennas for the experiments to be carried out in the divertor phase of the extended JET programme. The antenna plasma coupling problem is properly solved using a full wave solution which allows to incorporate the antenna array directivity and full asymmetric spectrum in the calculations. Current drive calculation at each step of the ray allows to take into account th power deposition profile and the electron trapping effects correctly. The poloidal field effects which change k// and therefore have important consequences on the current drive efficiencies are also taken into account. It is shown that current drive efficiency factor γ ≅ 0.11 in units of 1020 A/W/m2 is obtained for an electron temperature of 10 keV. Synergistic effects between the ICRH and the lower hybrid current drive system in which a population of fast electrons (≅ 100 - 200keV) is produced is also evaluated. It is found that a 0.5% concentration of 200 keV fast electrons would increase the current drive efficiency by 35% at a toroidal mode number n = 11 and this increase could be as large as a factor of 2 at lower n = 2-4

  13. Measurement of helicon wave coupling for current drive and anticipated role for high beta KSTAR plasmas

    Science.gov (United States)

    Wang, S. J.; Kim, H. J.; Joung, M.; Jeong, J. H.; Kim, J. H.; Bae, Y. S.; Kwak, J. G.; Wi, H. H.; Kim, H.-S.

    2015-11-01

    Helicon wave current drive has been suggested for efficient off-axis current drive in high electron beta tokamak plasmas. Fast wave drives centrally peaking current in the frequency range up to several ion cyclotron harmonics in the present tokamaks, such as KSTAR. Increasing fast wave frequency up to LH resonance frequency at the plasma edge, the spiral propagation of wave at the outer region of plasma lengthens the wave path to the plasma center. Also, optical thickness increases with frequency. It is expected that these effects produce efficient off-axis power deposition depending on the electron beta and magnetic field pitch. A low power TWA for helicon wave was installed and tested in KSTAR tokamak which is aiming for the steady-state high beta plasma requiring off-axis current drive. The power coupling properties of TWA at various plasma conditions will be presented. In addition to the coupling efficiency, issues such as load sensitivity and unwanted slow wave coupling will be addressed. Also, the simulation of plasma performance with the combination of helicon wave current drive and other conventional heating and current drive power in KSTAR will be discussed. This work was supported by the Korean Ministry of Science, ICT and Future Planning and by R&D Program through the National Fusion Research Institute of Korea (NFRI) funded by the Government funds.

  14. Energy Transport in the Steady State Plasma Sustained by DC Helicity Current Drive

    OpenAIRE

    K. Itoh; Itoh, S.-I.; Fukuyama, A.

    1992-01-01

    Steady state operation of tokamaks which is sustained by the DC helicity current drive near edge is studied. The necessary value of the current diffusivity is obtained. Relation between the current diffusivity and the thermal diffusivity, which are governed by the microscopic turbulence, indicates that this requires too large thermal transport for the parameters in present day experiments.

  15. Changing Chilean coastal currents could drive aquatic evolution

    Science.gov (United States)

    Schultz, Colin

    2012-01-01

    For invertebrate and fish species that spend most of their lives in rich coastal waters rather than migrating freely throughout the open ocean, the formation of island populations and the associated risk of genetic diversity loss are threats to long-term population health. Many species cope through a spawning mechanism whereby larvae are released en masse into near-shore ocean currents, like pollen adrift in the wind. The larvae are viable in open waters from days to months, but only those that find their way back to shore can settle and develop. To increase their chances, different species' larvae often use particular swimming behaviors, for example, varying their depth in the water column throughout the day.

  16. Ion collective acceleration and high current beam transport

    International Nuclear Information System (INIS)

    Results of investigation of high-current beam (HCB) transport in vacuum channels with dielectric walls (VCDW) are presented. It is shown, that HCB transport can be realized not only in rectilinear dielectric channels, but also in curvili also in curvilitear oges. In particular, it proved to be possible to bend the beam with parameters 50 kA, 400 keV by 90 deg. A problem of negative ion intense beam production is considered. It is shown, that in magnetic insulation diodes hydrogen ion currents of about several kA are obtained at current densities 10 A/cm2. Results of collective ion acceleration in VCDW are given. Two regions with different physical mechanisms of ion acceleration should be distinguished. In the first region (''plasma''), corresponding to HCB motion in VCDW ion generation and their acceleration in quasipotential field of HCB up to the energy of the order of electrons or less takes place. In the second region (''beam''), corresponding to joint motion of ''extracted'' ions and HCB electrons, ion acceleration takes place in the fields of waves, which can be excited due to the mechanism of two-beam instability type. Considerable contribution can also be made by stochastic mechanism of ion acceleration

  17. Nested folded-beam suspensions with low longitudinal stiffness for comb-drive actuators

    International Nuclear Information System (INIS)

    Nested folded-beam suspensions with a low longitudinal spring constant and a high lateral spring constant have been used in comb-drive actuators. In the new design, every two flexible beams and two stiff members form a parallelogram flexure, which is considered as an ‘element’ of the nested folded-beam suspension. A set of these flexures of increasing size were placed one outside another to compose a nested structure. In this way, a serial mechanical connection between adjacent parallelogram flexures was formed; thus, a longer output stroke was obtained by combining the stroke displacements of all flexures in an additive fashion. The designed suspensions were theoretically analyzed and numerically simulated. Furthermore, comb-drive actuators with conventional and new suspensions were fabricated and tested to verify the predicted function. In the testing cases, the longitudinal spring constants of suspensions with two (conventional), three and four parallelogram flexures on each side were measured as 2.77, 1.75 and 1.36 N m−1. The ratio among these three values was approximately 6:4:3, which is consistent with the theoretical predictions and simulation results. Microfabricated folded beams in series were achieved. (paper)

  18. The drive to strive: goal generation based on current needs

    Directory of Open Access Journals (Sweden)

    Elisabeth A Murray

    2013-06-01

    Full Text Available Hungry animals are influenced by a multitude of different factors when foraging for sustenance. Much of the work on animal foraging has focused on factors relating to the amount of time and energy animals expend searching for and harvesting foods. Models that emphasize such factors have been invaluable in determining when it is beneficial for an animal to search for pastures new. When foraging, however, animals also have to determine how to direct their search. For what food should they forage? There is no point searching for more of a particular food when you are sated from eating it. Here we review work in macaques and humans that has sought to reveal the neural circuits critical for determining the subjective value of different foods and associated objects in our environment and tracking this value over time. There is mounting evidence that a network composed of the orbitofrontal cortex (OFC, amygdala and medial thalamus is critical for linking objects in the environment with food value and adjusting those valuations in real time based on current biological needs. Temporal inactivation studies have revealed that the amygdala and OFC play distinct, but complementary roles in this valuation process. Such a network for determining the subjective value of different foods and, by extension, associated objects, must interact with systems that determine where and for how long to forage. Only by efficiently incorporating these two factors into their decisions will animals be able to achieve maximal fitness.

  19. Electron cyclotron current drive in low collisionality limit: On parallel momentum conservation

    International Nuclear Information System (INIS)

    A comprehensive treatment of the models used in ray- and beam-tracing codes to calculate the electron cyclotron current drive (ECCD) by means of the adjoint technique, based on the adjoint properties of the collision and Vlasov operators appearing in the drift-kinetic equation, is presented. Particular attention is focused on carefully solving the adjoint drift-kinetic equation (generalized Spitzer problem) with parallel momentum conservation in the like-particle collisions. The formulation of the problem is valid for an arbitrary magnetic configuration. Only the limit of low collisionality is considered here, which is of relevance for high-temperature plasmas. It is shown that the accurate solution of the adjoint drift-kinetic equation with parallel momentum conservation significantly differs (apart from the suprathermal electron portion) from that calculated in the high-speed-limit, which is most commonly used in the literature. For high-temperature plasmas with significant relativistic effects, the accuracy of the resulting numerical models is demonstrated by ray-tracing calculations and benchmark results are presented. It is found that the ECCD efficiency calculated for ITER with parallel momentum conservation significantly exceeds the predictions obtained with the high-speed-limit model.

  20. Consistency between current ramp-up/recharging scenario by non-inductive current drive and dense and cold divertor plasma

    International Nuclear Information System (INIS)

    Consistency between non-inductive current drive and the formation of cold and dense divertor plasma in phases of plasma current ramp-up and recharging. When we consider the current drive efficiency obtained in the experiments of JT-60 as the actual upper limit, it is difficult to realize the low plasma temperature below 50 eV near the divertor plate for the reasonable absorbed power (20MW) in FER. Divertor plasma temperature is reduced to about 20 eV for the absorbed power 30 MW. It is essentially important to increase the drive efficiency in order to attain the cold divertor plasma. When we use the slightly higher efficiency model than the experimental result of JT-60, the divertor plasma temperature will be reduced to 20 eV and about 10 eV for the absorbed power 20 MW and 30 MW respectively. (author)

  1. Analysis of electron current instability in E-beam writer

    Czech Academy of Sciences Publication Activity Database

    Bok, Jan; Horáček, Miroslav; Král, Stanislav; Kolařík, Vladimír; Matějka, František

    Ostrava : TANGER Ltd, 2012, s. 295-299. ISBN 978-80-87294-32-1. [NANOCON 2012. International Conference /4./. Brno (CZ), 23.10.2012-25.10.2012] R&D Projects: GA MŠk ED0017/01/01; GA TA ČR TE01020118; GA MPO FR-TI1/576 Institutional support: RVO:68081731 Keywords : electron beam * current measurement * current drift and noise * fourier analysis Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  2. Effects of Plasma Density and Toroidal Magnetic Field on Lower Hybrid Current Drive Efficiencv on HT-7 Tokamak

    Institute of Scientific and Technical Information of China (English)

    DING Bo-Jiang; YANG Chun-Sheng; XU Han-Dong; YU Jia-Wen; HUANG Yi-Yun; SHANG Lian-Quan; SHI Yue-Jiang; WU Zhen-Wei; ZHANG Jin-Song; YIN Fu-Xian; ZHANG Xiao-Dong; KUANG Guang-Li; LIU Xiao-Ning; XIE Ji-Kang; WAN Yuan-Xi; LIU Yue-Xiu; LIU Deng-Cheng; ZHENG Guang-Hua; WU Jun-Shuan; LIU Fu-Kun; SHEN Wei-Ci; LIN Jian-An

    2000-01-01

    Lower hybrid current drive experiments on the HT-7 device have been carried out by scanning the following parameters: central line averaged electron density (ne = 0.6 - 2.0 × 1019m-3) and toroidal magnetic field (Bt = 1.62 - 2.0 T). The dependence of current drive efficiency on these parameters has been studied and the experimental curves of current drive efficiency as a function of ne and Bt have also been obtained. From these experimental results, it can be seen that current drive efficiency rises with the increase of toroidal magnetic field. As plasma density increases, the current drive efficiency first increases to a certain value, then gradually decreases, that is, there exists an optimized density regime where a better drive efficiency can be obtained. The analysis shows that the current drive efficiency is mainly affected by wave accessibility and impurity concentration, and the competition of these two factors determines the current drive efficiency.

  3. On neutral-beam injection counter to the plasma current

    Science.gov (United States)

    Helander, P.; Akers, R. J.; Eriksson, L.-G.

    2005-11-01

    It is well known that when neutral beams inject ions into trapped orbits in a tokamak, the transfer of momentum between the beam and the plasma occurs through the torque exerted by a radial return current. It is shown that this implies that the angular momentum transferred to the plasma can be larger than the angular momentum of the beam, if the injection is in the opposite direction to the plasma current and the beam ions suffer orbit losses. On the Mega-Ampere Spherical Tokamak (MAST) [R. J. Akers, J. W. Ahn, G. Y. Antar, L. C. Appel, D. Applegate, C. Brickley et al., Plasma Phys. Controlled Fusion 45, A175 (2003)], this results in up to 30% larger momentum deposition with counterinjection than with co-injection, with substantially increased plasma rotation as a result. It is also shown that heating of the plasma (most probably of the ions) can occur even when the beam ions are lost before they have had time to slow down in the plasma. This is the dominant heating mechanism in the outer 40% of the MAST plasma during counterinjection.

  4. Practical application High-Tc SQUID beam current monitor

    International Nuclear Information System (INIS)

    To measure the DC current of heavy-ion beams non-destructively at high resolution, we have developed a high critical temperature (HTc) superconducting quantum interference device (SQUID) beam current monitor for use in the radioactive isotope beam factory (RIBF) at RIKEN. Unlike at other existing facilities, a low vibration, pulse-tube refrigerator cools the HTc fabrications including the SQUID in such a way that the size of the system is reduced and the running costs are lowered. Last year, the magnetic shielding system has been greatly reinforced. The new strong magnetic shielding system can attenuate the external magnetic noise to 10-10. Aiming at its practical use for acceleration operation, the prototype HTc SQUID monitor was disassembled, exchange the improved parts and re-assembled. Beginning this year, we have installed the HTc SQUID monitor in the beam transport line in the RIBF. Here we report the present details of the developed HTc SQUID monitor system and the results of the beam measurement. (author)

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Science.gov (United States)

    Simon, A.

    1998-11-01

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

  7. Beam position dependence of a wall-current monitor

    International Nuclear Information System (INIS)

    It was pointed out recently that there exists an appreciable beam position dependence in the wall-current monitor widely used in electron accelerators. Detailed study of this dependence is performed on a test bench varying the pulse width and the frequency of the input signal simulating the beam. The results of experiments show that when the pulse width becomes shorter more appreciable becomes the dependence, and it approaches to that of calculated from the method of images. A unified analysis is under way. (author)

  8. Squeezed state of high-current electron beam

    International Nuclear Information System (INIS)

    The results of the computer simulation of an electron beam propagating serially through two coaxial tubes with different radii are presented. It is shown that the virtual cathode in this system may be located in one of two positions depending on the injection current, variation of which yields fast movements of the potential barrier. Under certain conditions, a part of the beam may be in its squeezed state, forming, therefore, a cloud of a dense warm plasma. The qualitative analytical theory based on the consideration of the energy and momentum balance is also discussed

  9. Beam dynamics studies of high current RF and DTL tanks

    International Nuclear Information System (INIS)

    An accelerator for spallation breeding of fissile fuel must have low beam loss and high acceleration efficiency. An extensive investigation using the PARMTEQ and PARMILA computer beam dynamics codes has been undertaken to obtain a reference design for a 100% duty cycle 300 mA 10 MeV proton linac called ZEBRA (Zero Energy BReeder Accelerator) that could serve as the first stage of an accelerator-breeder. This paper discusses results of this investigation, showing how current carrying capacity and accelerating efficiency in both RFQ's and DTL's is affected by accelerator and injector parameters

  10. Collective monitors for high-current pulse electron beam diagnostics

    International Nuclear Information System (INIS)

    A collector monitor for high-current pulsed electron beams at average power of 100 W and pulse current of 100 A has been developed. The monitor comprises a Faraday cup, profile monitor, sector diaphragm, energy detector. The collector was fixed on a brass radiator transformed into a rod. The rod ensures reliable and electric contact of the collector with the ''earth'' and small RC of this line. Such design permits to stabilize the heat mode of the collector without utilization of external cooling. The monitors have been tested in electron beams at head load up to 100 W during 40 hours. Wear at the expense of evaporation, microexplosions were not observed. Accuracy of current measuring made up 5-10% for absolute and 1-2% for relative measurements

  11. A novel zero-current soft-switching converter for switched reluctance motor drives

    OpenAIRE

    Ching, TW; Chan, CC; Chan, MSW; Chau, KT

    1998-01-01

    A new zero-current-transition (ZCT) power converter for switched reluctance motor drive applications is presented. The proposed ZCT power converter possesses the definite advantages that both the main and auxiliary switches are operating with zero-current switching (ZCS), as well as minimum current and voltage stresses. It has a simple circuit topology, minimum component count and low cost. The ZCT technique can significantly reduce the switch-on or -off losses by forcing the current to zero ...

  12. A Smart Current Modulation Scheme for Harmonic Reduction in Three- Phase Motor Drive Applications

    OpenAIRE

    Davari, Pooya; Zare, Firuz; Blaabjerg, Frede

    2015-01-01

    Electric motor-driven systems consume considerable amount of the global electricity. Majority of three-phase motor drives are equipped with conventional diode rectifier and passive harmonic mitigation, being witnessed as the main source in generating input current harmonics. While many active harmonic mitigation methods have been developed over the years, the total cost and complexity has become the main obstacle in employing prior-art methods for motor drive systems. This paper presents a no...

  13. Modeling of the electron distribution based on bremsstrahlung emission during lower hybrid current drive on PLT

    International Nuclear Information System (INIS)

    Lower hybrid current drive requires the generation of a high energy electron tail anisotropic in velocity. Measurements of bremsstrahlung emission produced by this tail are compared with the calculated emission from reasonable model distributions. The physical basis and the sensitivity of this modeling process are described and the plasma properties of current driven discharges which can be derived from the model are discussed

  14. The effect of toroidal field on the rotating magnetic field current drive in rotamak plasmas

    Institute of Scientific and Technical Information of China (English)

    Zhong Fang-Chuan; Huang Tian-Sen; Petrov Yuri

    2007-01-01

    A rotamak is one kind of compact spherically shaped magnetic-confinement device. In a rotamak the plasma current is driven by means of rotating magnetic field (RMF). The driven current can reverse the original equilibrium field and generate a field-reversed-configuration. In a conventional rotamak, a toroidal field (TF) is not necessary for the RMF to drive plasma current, but it was found that the present of an additional TF can influence the RMF current drive. In this paper the effect of TF on the RMF current drive in a rotamak are investigated in some detail.The experimental results show that addition of TF increases the RMF driven current greatly and enhances the RMF penetration dramatically. Without TF, the RMF can only penetrate into plasma in the edge region. When a TF is added, the RMF can reach almost the whole plasma region. This is an optimal strength of toroidal magnetic field for getting maximum plasma current when Bv and radio frequency generator power are fixed. Besides driving current,the RMF generates high harmonic fields in rotamak plasma. The effect of TF on the harmonic field spectra are also reported.

  15. Progress in EC heating and current drive physics and technology at RTP

    International Nuclear Information System (INIS)

    Recent achievements in both the technical development program and the experimental physics program related to electron cyclotron waves are described: - first lasing of the Free Electron Maser; - feedback control of the gyrotron output;- second harmonic current drive experiments; - control of the current decay in disruptions; -cross- polarisation scattering experiments. (author)

  16. Progress in EC heating and current drive physics and technology at RTP

    International Nuclear Information System (INIS)

    Recent achievements in both the technical development program and the experimental physics program related to electron cyclotron waves are described: first lasing of the Free Electron Maser; feedback control of the gyrotron output; second harmonic current drive experiments; control of the current decay in disruptions; cross-polarisation scattering experiments. (author)

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

    Science.gov (United States)

    Parke, E.

    2015-11-01

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

  18. Numerical modelling of lower hybrid RF heating and current drive experiments in the Alcator C tokamak

    International Nuclear Information System (INIS)

    A simulation model is described for lower hybrid (LH) current drive, rampup, heating, and sawtooth stabilization. The model incorporates a one-dimensional radial transport code, parallel velocity Fokker-Planck calculation, and a toroidal ray tracing code. For steady LH current drive it is found that the RF current generation is accurately predicted by a fast electron confinement time of the form τL=τ0(±)γ3, with τ0(±)=3ms in the density range of 3x1019m-3 e 19m-3 (where ± distinguishes electrons moving parallel (antiparallel) to the current drive direction). Also in this range, the theoretically predicted wave absorption and experimentally measured electron temperatures and stored energy were found to be consistent with an electron thermal diffusivity whose magnitude is independent of ne. To reproduce the experimentally measured values of LH rampup efficiency at n-bare=3x1019m-3, it was necessary to take τ0(±)=3ms. For LH heating at densities of n-bare approx.= 1.4x1020m-3, the power lost due to collisional damping of the LH ray trajectories at the plasma periphery was found to be significant, because of higher edge densities. Studies of LHRF sawtooth stabilization experiments with RF current drive indicated the possibility of creating stable profiles of the safety factor, q, via the generation of positive RF current near the q=1 surface, thus producing a current 'pedestal'. (author). 41 refs, 13 figs, 3 tabs

  19. Investigation of lower hybrid current drive during H-mode in EAST tokamak

    Institute of Scientific and Technical Information of China (English)

    Li Miao-Hui; Liu Fu-Kun; Wang Mao; Xu Han-Dong; Wan Bao-Nian; Ding Bo-Jiang; Kong Er-Hua; Zhang Lei; Zhang Xin-Jun; Qian Jin-Ping; Yan Ning; Han Xiao-Feng; Shan Jia-Fang

    2011-01-01

    H-mode discharges with lower hybrid current drive (LHCD) alone are achieved in EAST divertor plasma over a wide parameter range.These H-mode discharges are characterized by a sudden drop in Dα emission and a spontaneous rise in main plasma density.Good lower hybrid (LH) coupling during H-mode is obtained by putting the plasma close to the antenna and by injecting D2 gas from a pipe near the grill mouse.The analysis of lower hybrid current drive properties shows that the LH deposition profile shifts off axis during H-mode,and current drive (CD) efficiency decreases due to the increase in density.Modeling results of H-mode discharges with a general ray tracing code GENRAY are reported.

  20. U.S.-Japan workshop on 'RF heating and current drive in confinement systems tokamaks'

    International Nuclear Information System (INIS)

    The workshop was attended by 8 US scientists and 30 Japanese scientists. The agenda was divided into 2 1/2 days of presentation, 1/2 day group discussions and 1/2 day summary session. There were 10 papers on rf physics, technologies and applications; 6 papers on new concepts, helicity injection and transport; and 6 papers on heating/current drive and scrape-off-layer/divertor conditions. The wide range of topics discussed is an indication of the impressive growth, both in depth and breadth, of the US-Japan workshop in RF Heating and Current Drive. It also benefitted by being combined with the new current drive concepts workshops and the active participation of JAERI scientists. (J.P.N.)

  1. Neoclassical current effects in neutral beam-heated tokamaks

    International Nuclear Information System (INIS)

    There is a long-standing prediction from neoclassical theory that strong contributions to the toroidal current should be driven by friction between trapped and passing particles when β/sub pol/ exceeds √R/a in a tokamak. A number of neutral beam heating experiments can now produce such parameters, and it is of interest to calculate the behavior which should occur in this regime to determine the feasibility of using such a bootstrap current as a steady-state tokamak current source. Since gross manifestations are absent in a wide range of experiments on the Impurity Study Experiment (ISX-B), as reported earlier, the conclusion is that the neoclassical current, if present, can have a value no larger than 25% of its theoretically calculated value. Since the neoclassical particle (Ware) pinch is strongly related to the neoclassical current in the theory (Onsager reciprocity), the existence of the particle pinch is thus called into question

  2. Electron beam induced current in photovoltaics with high recombination

    OpenAIRE

    Haney, Paul M.; Yoon, Heayoung P.; Koirala, Prakash; Collins, Robert W.; Zhitenev, Nikolai B.

    2014-01-01

    Electron beam induced current (EBIC) is a powerful characterization technique which offers the high spatial resolution needed to study polycrystalline solar cells. Ideally, an EBIC measurement reflects the spatially resolved quantum efficiency of the device. In this work, a model for EBIC measurements is presented which applies when recombination within the depletion region is substantial. This model is motivated by cross-sectional EBIC experiments on CdS-CdTe photovoltaic cells which show th...

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

    International Nuclear Information System (INIS)

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

  4. Heating, current drive and transport properties of large area ICRF couplers

    International Nuclear Information System (INIS)

    Initially, the large area ICRF couplers were studied in Macrotor in order to minimize the effects of the RF on the edge plasma and on the related transport. Recently, the following three aspects of these couplers have been studied. (1) Reduction of the edge power density by size alone. (2) Formation of a narrow K-parallel spectrum. (3) The utilization of this powerful technique for fast wave lower hybrid current drive generation. Current drive experiments in Macrotor have resulted in the prediction that a continuously driven tokamak operation can be achieved at a level that will be consistent with neo-Alcator scaling

  5. X-ray analysis of nonMaxwellian distributions (current drive)

    International Nuclear Information System (INIS)

    The plasma bremsstrahlung emission is utilized to determine the shape of the electron velocity distribution in situations where it deviates strongly from a Maxwellian distribution. The instrumentation used to measure the hard x-ray emission is briefly discussed. Model calculations show that polarization measurements give best results for unrelativistic tails with tail temperatures T/sub b/ 50 keV. The techniques were originally developed in order to analyze runaway discharges. Recently, they found new interest because of the formation of energetic electron tails during current drive. The first x-ray results from the current drive during LH heating on PLT are discussed

  6. Analysis of JET LCHD/ICRH synergy experiments in terms of relativistic current drive theory

    Energy Technology Data Exchange (ETDEWEB)

    Start, D.F.H.; Baranov, Y.; Brusati, M.; Ekedahl, A.; Froissard, P.; Gormezano, C.; Jacquinot, J.; Paquin, L.; Rimini, F.G. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Cox, M.; Gardner, C.; O`Brien, M.R. [UKAEA Culham Lab., Abingdon (United Kingdom); Di Vita, A. [Ansaldo SpA, Genoa (Italy)

    1994-07-01

    The present analysis shows that the observed efficiency of current drive with synergy between LHCD and ICRH is in good agreement with the relativistic theory of Karney and Fisch for Landau damped waves. The predicted power absorption from the fast wave by the electron tail is within 30% of the measured value. In the presence of significant fast electron diffusion within a slowing down time it would be possible to produce central current drive using multiple ICRF resonances even when the LHCD deposition is at half radius, as in an ITER type device. (authors). 4 refs., 6 figs.

  7. Modelling Ion Cyclotron Resonance Heating and Fast Wave Current Drive in Tokamaks

    OpenAIRE

    Hannan, Abdul

    2013-01-01

    Fast magnetosonic waves in the ion cyclotron range of frequencies have the potential to heat plasma and drive current in a thermonuclear fusion reactor. A code, SELFO-light, has been developed to study the physics of ion cyclotron resonantheating and current drive in thermonuclear fusion reactors. It uses a global full wave solver LION and a new 1D Fokker-Planck solver for the self-consistent calculations of the wave field and the distribution function of ions.In present day tokamak experimen...

  8. A Smart Current Modulation Scheme for Harmonic Reduction in Three- Phase Motor Drive Applications

    DEFF Research Database (Denmark)

    Davari, Pooya; Zare, Firuz; Blaabjerg, Frede

    2015-01-01

    Electric motor-driven systems consume considerable amount of the global electricity. Majority of three-phase motor drives are equipped with conventional diode rectifier and passive harmonic mitigation, being witnessed as the main source in generating input current harmonics. While many active...... harmonic mitigation methods have been developed over the years, the total cost and complexity has become the main obstacle in employing prior-art methods for motor drive systems. This paper presents a novel current modulation method based on the electronic inductor concept for three-phase ac-dc systems to...

  9. Hot electrical conductivity in lower hybrid current drive plasmas in the HT-7 tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Z.Y. [Department of Physics, Yunnan Normal University, Kunming 650092 (China) and Key Laboratory of Advanced Technology and Manufacture for Renewable Energy Material, Ministry of Education, Kunming 650092 (China)], E-mail: chenzy1003@163.com; Ju, H.J. [Department of Physics, Yunnan Normal University, Kunming 650092 (China); Wan, B.N.; Gao, H.X.; Sajjad, S.; Shi, Y.J. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2008-06-02

    The interaction between the hot electrical conductivity and the residual electric field have been investigated in lower hybrid current drive (LHCD) experiments with non-zero loop voltage in the HT-7 tokamak. It has been found that the hot electrical conductivity contribute significantly to the current drive in partial non-inductively sustained plasmas. The hot electrical conductivities under different lower hybrid power levels and different parallel refractive indexes have been obtained. It is comparable to the Spitzer conductivity in high power LHCD experiments.

  10. Hot electrical conductivity in lower hybrid current drive plasmas in the HT-7 tokamak

    International Nuclear Information System (INIS)

    The interaction between the hot electrical conductivity and the residual electric field have been investigated in lower hybrid current drive (LHCD) experiments with non-zero loop voltage in the HT-7 tokamak. It has been found that the hot electrical conductivity contribute significantly to the current drive in partial non-inductively sustained plasmas. The hot electrical conductivities under different lower hybrid power levels and different parallel refractive indexes have been obtained. It is comparable to the Spitzer conductivity in high power LHCD experiments

  11. Implications of ITER requirements on R and D of RF heating and current drive systems

    International Nuclear Information System (INIS)

    Heating and Current Drive (H and CD) systems have an essential role in ITER-FEAT operation, as all phases of ITER operation are driven and controlled by the auxiliary power flow. The RF (Electron Cyclotron and Ion Cyclotron) systems, planned to contribute for ∼ 60% of the total auxiliary power (72 MW), with Lower Hybrid used for the specialised function of current drive in the extended performance phase (20 MW), are at different level of technology development. All systems, need a significant development in order to meet ITER operation requirements In this paper these requirements are reviewed and CEA proposals for the development of the Ion cyclotron system presented. (author)

  12. Compensation methods applied in current control schemes for large AC drive systems

    DEFF Research Database (Denmark)

    Rus, D. C.; Preda, N. S.; Teodorescu, Remus; Imecs, M.

    The paper deals with modified PI current control structures for large AC drive systems which use surface mounted permanent magnet synchronous machines or squirrel-cage induction motors supplied with voltage source inverters. In order to reduce the power losses caused by high frequency switching of...... the semiconductor devices, various compensation methods are used and a modified structure for a PI current controller is proposed, to reduce the switching frequency of the inverter for the same operating frequency of the drive. Simulation, experimental development and test results are presented in...

  13. Beta effects on rf-driven current profile and driving efficiency in reversed field pinch plasma

    International Nuclear Information System (INIS)

    The current density profile in reversed field pinch (RFP) plasma is controlled by rf current drive using a single-ray fast magnetosonic wave (FMW; f - 10fDC, fDC is deuteron cyclotron frequency). This paper reports more detailed beta effects on both the current density profile and the current driving efficiency with a fixed wave parameters. Any increase of beta value due to either increase of electron temperature Te0(0) or density ne0(0) makes the force-free current distribution more flat in the inner region. Increasing Te0(0) at a fixed higher beta value enhances the rf-driven current and the magnetic shear, but a positive gradient of force-free current which makes m=1 tearing mode unstable. There is an optimum Te0(0) value which maximizes the region of constant force-free current not having its positive gradient, although its positive gradient can be also controlled by adjusting wave parameters. Then the global current driving efficiency is lower rather than that for the lower beta plasma. (author)

  14. Lower hybrid heating and current drive in Iter operation scenarios and outline system design

    International Nuclear Information System (INIS)

    Lower Hybrid Waves (LHW) are considered a valid method of plasma heating and the best demonstrated current drive method. Current drive by LHW possesses the unique feature, as compared to the other methods, to retain a good current drive efficiency in plasma regions of low to medium temperature, or in low-β phases of the discharges. This makes them an essential element to realize the so called 'advanced steady-state Tokamak scenarios' in which a hollow current density profile (deep shear reversal) - established during the ramp-up of the plasma current - offers the prospects of improved confinement and an MHD-stable route to continuous burn. This report contains both modelling and design studies of an LHW system for ITER. It aims primarily at the definition of concepts and parameters for steady-state operation using LHW combined with Fast Waves (FW), or other methods of generating a central seed current for high bootstrap current operation. However simulations addressing the use of LHW for current profile control in the high current pulsed operation scenario are also presented. The outline design of a LHW system which covers the needs for both pulsed and steady-state operation is described in detail. (author). 28 refs., 49 figs

  15. Extracting DC bus current information for optimal phase correction and current ripple in sensorless brushless DC motor drive

    Institute of Scientific and Technical Information of China (English)

    Zu-sheng HO; Chii-maw UANG; Ping-chieh WANG

    2014-01-01

    Brushless DC motor (BLDCM) sensorless driving technology is becoming increasingly established. However, op-timal phase correction still relies on complex calculations or algorithms. In finding the correct commutation point, the problem of phase lag is introduced. In this paper, we extract DC bus current information for auto-calibrating the phase shift to obtain the correct commutation point and optimize the control of BLDC sensorless driving. As we capture only DC bus current information, the original shunt resistor is used in the BLDCM driver and there is no need to add further current sensor components. Software processing using only simple arithmetic operations successfully accomplishes the phase correction. Experimental results show that the proposed method can operate accurately and stably at low or high speed, with light or heavy load, and is suitable for practical applications. This approach will not increase cost but will achieve the best performance/cost ratio and meet market expectations.

  16. Lower hybrid heating and current drive in ignitor shear reversal scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Barbato, E.; Pinaccione, L. [Italian Agengy for New Technologies, Energy and the Environment, Centro Ricerche Frascati, Rome (Italy). Dip. Energia

    1996-05-01

    Injection of Lower Hybrid (LH) Wave power at 8 GHz is considered into IGNITOR shear reversal scenarios, characterized by a reduced plasma current and density. Power deposition calculation are performed to establish whether LH waves can be used both as central heating and off axis current drive tool. It turns out that LH waves can be used (a) for central plasma heating purpose during the current vamp phase, to freeze the shear reversed configuration, at the power level of {approx}10 MW. (b) to drive a current in the outer part of the plasma at the power level of 20 MW. In this way around 1/3-1/6 of the total current in the proper plasma position (i.e. where q is minimum) is driven.

  17. Theory and experiments on RF plasma heating, current drive and profile control in TORE SUPRA

    International Nuclear Information System (INIS)

    This paper reviews the main experimental and theoretical achievements related to the study of RF heating and non-inductive current drive and particularly phenomena related to the current density profile control and the potentiality of producing stationary enhanced performance regimes: description of the Lower Hybrid (LH) and Ion Cyclotron Resonant Frequency (ICRF) systems; long pulse coupling performance of the RF systems; observation of the transition to the so-called ''stationary LHEP regime'' in which the (flat) central current density and (peaked) electron temperature profiles are fully decoupled; experiments on ICRF sawtooth stabilization with the combined effect of LHCD modifying the current density profile; diffusion of fast electrons generated by LH waves; ramp-up experiments in which the LH power provided a significant part of the resistive poloidal flux and flux consumption scaling; theory of spectral wave diffusion and multipass absorption; fast wave current drive modelling with the Alcyon full wave code; a reflector LH antenna concept. 18 figs., 48 refs

  18. Shaping of electron beam picosecond current pulses in waveguide accelerators

    International Nuclear Information System (INIS)

    Results are given of experiments on extracting a single bunch in an experimental SHF wavegujde accelerator operating in the stoped energy mode. The accelerator has the following parameters: 8 MeV energy, 1818 MHz frequency of the accelerating field, 10 ns pulse duration of current; 20 A pulsed current, operation in the mode of single massages. An electron beam in the shape of a 10 ns pulse has been injected into the waveguide at the end of a SHF-pulse. The shape of detected picosecond pulses of accelerated electron current is close to triangular one, pulse duration at half-height with correction for rise time of the measuring system is equal to 50 ps, pulse current is about 100 A, electron energy equals 8 MeV

  19. Sensitivity improvement of beam current monitor with a high-Tc current sensor and SQUID

    International Nuclear Information System (INIS)

    It is widely recognized that non-destructive measurement at high resolution of the DC current of high-energy heavy-ion beams is important. Therefore, a high critical temperature (HTc) superconducting quantum interference device (SQUID) beam current monitor has been developed for use in the radioactive isotope beam factory (RIBF) at RIKEN in Japan. Unlike at other existing facilities, a low-vibration, pulse-tube refrigerator cools the HTc fabrications including the SQUID in such a way that the size of the system is reduced and the running costs are lowered. As a result, using a prototype of the HTc SQUID monitor, the intensity of a 4 μA Xe beam (10.8 MeV/u) was successfully measured with 100 nA resolution. Furthermore, since higher resolution is necessary, development of an improved HTc current sensor with two coils has begun. A spaying machine was developed to fabricate the new HTc current sensor by dip-coating a thin layer of Bi2-Sr2-Ca2-Cu3-Ox (Bi-2223) onto a 99.7% MgO ceramic substrate. Results from a new HTc current sensor produced using this machine are reported here. (author)

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

    International Nuclear Information System (INIS)

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

  1. Current to frequency converter for digitization of millisecond beam signals

    International Nuclear Information System (INIS)

    Beam-intensity monitoring in the Fermilab Neutrino Area requires sensitive and fast processing for beam signals (with four or five decade amplitude variations for a typical detector) which are digitized with a current-to-frequency converter (IFC). The converter digitizes the input charge at a 1 pC/Hz rate with a processing limit at 10 MHz for a 10 nC charge input or a 10 ;mu;A current input. For a 1 ms beam pulse, the IFC can generate a 1 to 10,000 count output. The digitizer is two to three decades more sensitive than the fastest commercial V to F converters and the upper frequency limit is two or three decades higher than the present laboratory built IFC's. The resolution over the 0 to 50 C temperature range and the linearity from 1 Hz to 1 MHz is held to ;plus or minus;1% with a linearity deviation of +5% at 10 MHz. 3 refs

  2. Beam current transformer (BCT) for experiment WA1/2

    CERN Multimedia

    1978-01-01

    In experiment WA1/2, a 400 GeV proton beam from the SPS was directed at a target, downstream of which a hadron line selected, in several narrow momentum bands, a beam of either pi+ and K+ or pi- and K-. These neutrino-parent particles, before entering a 292 m long decay tunnel, passed through a set of 2 BCTs of a design seen here. They measured the hadron intensity (10^10 to 10^11 particles/pulse) with a precision of the order of 1%. There were 2 of them, for enhanced precision and confidence. After the discovery of neutral currents in the Gargamelle-experiment, WA1/2 was the first follow-up, high-precision experiment (Z.Phys.C35, 443-452, 1987 and Z.Phys.C45, 361-379, 1990). See also 7706516X.

  3. Collective ion acceleration in high current relativistic electron beams

    International Nuclear Information System (INIS)

    This report describes the progress made during the current contract period investigating the use of high power relativistic electron beams for electron and ion acceleration. Section 2 gives a summary of results from the relativistic klystron experiment and details our plans for a large diameter coaxial system. Section 3 summarizes our efforts to generate upper hybrid waves on relativistic electron beams. Simulation work of the upper hybrid excitation process is reported. Our experiment using high power microwaves for electron acceleration is discussed. This paper also reports progress on development of repetitive pulsed experimental and data acquisition systems. Our future research plans are outlined, followed by a list of publications and presentations from our present work. 10 figs

  4. Fast wave current drive modeling using the combined RANT3D and PICES Codes

    International Nuclear Information System (INIS)

    Two numerical codes are combined to give a theoretical estimate of the current drive and direct electron heating by fast waves launched from phased antenna arrays on the DIII-D tokamak. Results are compared with experiment. copyright 1996 American Institute of Physics

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

    International Nuclear Information System (INIS)

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

  6. Theory of free-electron-laser heating and current drive in magnetized plasmas

    International Nuclear Information System (INIS)

    The introduction of a powerful new microwave source, the free-electron laser, provides new opportunities for novel heating and current-drive schemes to be used in toroidal fusion devices. This high-power, pulsed source has a number of technical advantages for these applications, and its use is predicted to lead to improved current-drive efficiencies and opacities in reactor-grade fusion plasmas in specific cases. The Microwave Tokamak Experiment at the Lawrence Livermore National Laboratory will provide a test for some of these new heating and current-drive schemes. Although the motivation for much of this research has derived from the application of a free-electron laser to the heating of a tokamak plasma at a frequency near the electron cyclotron frequency, the underlying physics, i.e., the highly nonlinear interaction of an intense, pulsed, coherent electromagnetic wave with an electron in a magnetized plasma including relativistic effects, is of general interest. Other relevant applications include ionospheric modification by radio-frequency waves, high-energy electron accelerators, and the propagation of intense, pulsed electromagnetic waves in space and astrophysical plasmas. This review reports recent theoretical progress in the analysis and computer simulation of the absorption and current drive produced by intense pulses, and of the possible complications that may arise, e.g., parametric instabilities, nonlinear self-focusing, trapped-particle sideband instability, and instabilities of the heated plasma

  7. Study on Current Sensorless Vector Control Method for Electric Vehicle Drive Motor

    Directory of Open Access Journals (Sweden)

    Xiaoyong Shen

    2013-07-01

    Full Text Available With the aggravation of environment pollution and the reduction of petroleum resources, the development of electric vehicle (EV draws more and more people’s attention. In the EV research field, that seeking for a high efficient and reliable motor control method that suits the operating conditions and characteristics of the vehicle drive motor has become one of the key techniques that need to be broken through urgently. Owing to the problems that the efficient work area is narrow and it leads to over-current phenomenon when traditional motor vector control method is applied to vehicle drive motor, this paper presents a current sensorless vector control technique for electric vehicle drive motor. According to motor speed and command torque which is gained from the speed loop control, this method directly controls the magnitude and phase angle of voltage vector to realize the orientation control of the magnetic field and then achieve the purpose of controlling the motor torque and speed. The feasibility and effectiveness of this method are verified by simulation results and bench test. Moreover, this method can not only improve the efficient work area, but also increase the reliability of motor control system. At the same time, it overcomes the dependence on the current sensor, circumvents the over-current defect caused by traditional motor vector control approach and reduces its cost. So it is a suitable and efficient control method for electric vehicle drive motor.  

  8. Mode-converted electron Bernstein waves for heating and current drive in NSTX

    International Nuclear Information System (INIS)

    The power coupled to electron Bernstein waves in a triplet mode conversion resonator from a fast X-mode at the plasma edge in NSTX is shown to be > 80% for fce ce. The EBW damping in the plasma is strong and localized and, thus, should be useful for heating, current drive, or profile control. (author)

  9. Modeling of the influences of electron cyclotron current drive on neoclassical tearing modes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Long; Liu, Jinyuan; Sun, Jizhong, E-mail: jsun@dlut.edu.cn [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Sun, Guanglan [Basic Science Section, North China Institute of Aerospace Engineering, Langfang 065000 (China); Duan, Ping [Department of Physics, Dalian Maritime University, Dalian 116026 (China)

    2015-05-15

    Influences of external current drive on neoclassical tearing modes are studied numerically with a set of compressible magnetohydrodynamics equations. By considering the effects of driven current parameters and its deposition timing, and by examining the relationship between driven current and the missing bootstrap current, the basic requirements of deposition width and external current density for effectively suppressing neoclassical tearing modes are investigated. When the driven current density is able to compensate the missing bootstrap current and the deposition region is comparable with the saturated island, the suppression results are notable. Meanwhile, the pre-emptive strategy of current deposition reported experimentally is also evaluated, and the results agree with the experimental ones that early current deposition can enhance suppression effectiveness greatly. In addition, the deficiencies of continuous driven current are discussed when the plasma rotation has been taken into account, and the application of modulated current drive, which is synchronized in phase with the rotating island, can restore the stabilizing role under some conditions. The favorable parameters of modulation such as duty cycle are also addressed.

  10. Modeling of the influences of electron cyclotron current drive on neoclassical tearing modes

    International Nuclear Information System (INIS)

    Influences of external current drive on neoclassical tearing modes are studied numerically with a set of compressible magnetohydrodynamics equations. By considering the effects of driven current parameters and its deposition timing, and by examining the relationship between driven current and the missing bootstrap current, the basic requirements of deposition width and external current density for effectively suppressing neoclassical tearing modes are investigated. When the driven current density is able to compensate the missing bootstrap current and the deposition region is comparable with the saturated island, the suppression results are notable. Meanwhile, the pre-emptive strategy of current deposition reported experimentally is also evaluated, and the results agree with the experimental ones that early current deposition can enhance suppression effectiveness greatly. In addition, the deficiencies of continuous driven current are discussed when the plasma rotation has been taken into account, and the application of modulated current drive, which is synchronized in phase with the rotating island, can restore the stabilizing role under some conditions. The favorable parameters of modulation such as duty cycle are also addressed

  11. Numerical study on the stabilization of neoclassical tearing modes by electron cyclotron current drive

    International Nuclear Information System (INIS)

    It is well known that electron cyclotron current drive (ECCD) around the o-point of magnetic island along the plasma current direction can stabilize neoclassical tearing modes (NTMs) in tokamak devices. The effects of the radial misalignment between the island and the driven current, the phase misalignment, and the on-duty ratio for modulated current drive on NTM stabilization are studied numerically in this paper. A small radial misalignment is found to significantly decrease the stabilizing effect. When a sufficiently large phase misalignment occurs for the modulated ECCD, the stabilization effect is also reduced a lot. The optimal on-duty ratio of modulated ECCD to stabilize NTMs is found to be in the range of 60%–70%. A larger on-duty ratio than 50% could also mitigate the effect of phase misalignment if it is not too large. There is no benefit from modulation if the phase misalignment is larger than a threshold

  12. Numerical study on the stabilization of neoclassical tearing modes by electron cyclotron current drive

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaoguang; Zhang, Xiaodong; Wu, Bin; Zhu, Sizheng; Hu, Yemin [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei (China)

    2015-02-15

    It is well known that electron cyclotron current drive (ECCD) around the o-point of magnetic island along the plasma current direction can stabilize neoclassical tearing modes (NTMs) in tokamak devices. The effects of the radial misalignment between the island and the driven current, the phase misalignment, and the on-duty ratio for modulated current drive on NTM stabilization are studied numerically in this paper. A small radial misalignment is found to significantly decrease the stabilizing effect. When a sufficiently large phase misalignment occurs for the modulated ECCD, the stabilization effect is also reduced a lot. The optimal on-duty ratio of modulated ECCD to stabilize NTMs is found to be in the range of 60%–70%. A larger on-duty ratio than 50% could also mitigate the effect of phase misalignment if it is not too large. There is no benefit from modulation if the phase misalignment is larger than a threshold.

  13. Optimum Torque/Current Control of Dual-PMSM Single-VSI Drive

    OpenAIRE

    Andrea Del Pizzo; Diego Iannuzzi; Ivan Spina

    2010-01-01

    The paper deals with isotropic PM-brushless drives in configuration “single-inverter, dual-motor” operating with unbalanced load-torques. An innovative control algorithm is presented. It is suitable to minimize the resultant armature current needed to obtain an assigned resultant motor torque, whatever is the load unbalance. Simplified analytical expressions are given in order to quickly evaluate optimized reference currents with good approximation. From these reference values, a predictive f...

  14. Achievement of second stability by means of lower hybrid current drive

    Energy Technology Data Exchange (ETDEWEB)

    Bonoli, P.T.; Porkolab, M. (Plasma Fusion Center, MIT, Cambridge, MA (USA)); Blackfield, D.T. (TRW/LLNL, Redondo Beach, CA (USA)); Devoto, R.S.; Fenstermacher, M.E. (LLNL, Livermore, CA (USA))

    1989-07-01

    It is shown that profiles of the safety factor, necessary to access a high beta operating regime in shaped, low aspect ratio tokamaks, can be achieved via off-axis lower hybrid current drive (LHCD). In order to accurately access this RF current generation, a simulation model for LHCD has been extended to noncircular equilibria and combined with an MHD equilibrium solver. Model results will be presented for Versator Upgrade parameters.

  15. Sawtooth control by on-axis electron cyclotron current drive on the WT-3 tokamak

    International Nuclear Information System (INIS)

    The experiments on control of sawtooth oscillations (STO) by electron cyclotron current drive (ECCD) have been performed on the WT-3 tokamak. Stabilization and excitation of STO are observed for counter-ECCD and co-ECCD, respectively, when the position of the power deposition is located inside the inversion radius. These results are due to the modification of the current profile near the magnetic axis. (author)

  16. Mapping ion beam induced current changes in a commercial MOSFET

    Energy Technology Data Exchange (ETDEWEB)

    Alves, A.D.C.; Thompson, S.; Yang, C. [School of Physics, University of Melbourne, Victoria 3010 (Australia); Jamieson, D.N., E-mail: d.jamieson@unimelb.edu.au [School of Physics, University of Melbourne, Victoria 3010 (Australia)

    2011-10-15

    We demonstrate a novel nuclear microprobe imaging and analysis modality for micrometre-scale field effect transistor devices probed with focused beams of MeV ions. By recording the drain current as a function of time during ion irradiation it is possible to identify current transients induced by the passage of single ions through the sensitive structures of the device. This modality takes advantage of the fact that the ionization produced by the passage of a single ion acts in an equivalent way to a transient change in the gate bias which therefore modulates the drain current as a function of time. This differs from the traditional ion beam induced charge technique where the ionization drifts in an internal electric field and induces a single charge pulse in an electrode applied to the device. Instead a richer variety of phenomena are observed, with different time constants which depend on the proximity of the ion strike to the channel of the device. The signals may be used to examine device function, radiation sensitivity or to count ion impacts within the channel.

  17. Neoclassical current effects in neutral-beam-heated tokamak discharges

    International Nuclear Information System (INIS)

    There is a long-standing prediction from neoclassical theory that strong contributions to the toroidal current should be driven by friction between trapped and passing particles when βsub(pol) exceeds root (R/a) in a tokamak. A number of neutral-beam heating experiments can now produce such parameters, and it is of interest to calculate the behaviour which should occur in this regime to determine the feasibility of using such a 'bootstrap' current as a steady-state tokamak current source. It is found that the neoclassical current should be large enough to reverse the external loop voltage for typical experimental parameters (ISX-B, in particular) in cases where the total current is fixed and to produce a detectable excess of total current above the pre-programmed (demand) value in cases where the loop voltage is regulated. Other manifestations of such a current should be either: a sharp rise in the central q-value (producing a cessation of internal m=1 and m=2 MHD activity), with an enhancement by two orders of magnitude of ion thermal conductivity (due to the formation of a hollow current density profile and a consequent drop in local values of the poloidal magnetic field in the central plasma region), or an enhanced tendency for disruption (arising from magnetic reconnection in hollow-profile equilibria). Since these gross manifestations are absent in a wide range of experiments on the Impurity Study Experiment (ISX-B), as reported earlier, the conclusion is that the neoclassical current, if present, can have a value no larger than 25% of its theoretically calculated value. Since the neoclassical particle (Ware) pinch is strongly related to the neoclassical current in the theory (Onsager reciprocity), the existence of the particle pinch is thus called into question. (author)

  18. $2\\times250$ GeV CLIC $\\gamma\\gamma$ Collider Based on its Drive Beam FEL

    CERN Document Server

    Aksakal, Husnu

    2007-01-01

    CLIC is a linear $e^+e^-$ ($\\gamma\\gamma$) collider project which uses a drive beam to accelerate the main beam. The drive beam provides RF power for each corresponding unit of the main linac through energy extracting RF structures. CLIC has a wide range of center-of-mass energy options from 150 GeV to 3 TeV. The present paper contains optimization of Free Electron Laser (FEL) using one bunch of CLIC drive beam in order to provide polarized light amplification using appropriate wiggler and luminosity spectrum of $\\gamma\\gamma$ collider for $E_{cm}$=0.5 TeV. Then amplified laser can be converted to a polarized high-energy $\\gamma$ beam at the Conversion point (CP-prior to electron positron interaction point) in the process of Compton backscattering. At the CP a powerful laser pulse (FEL) focused to main linac electrons (positrons). Here this scheme described and it is show that CLIC drive beam parameters satisfy the requirement of FEL additionally essential undulator parameters has been defined. Achievable $\\g...

  19. Electron cyclotron heating and current drive on Tore Supra 2002-2005

    International Nuclear Information System (INIS)

    The ECRH/ECCD (electron cyclotron resonance heating/electron cyclotron corral drive) system on Tore Supra, with its front steering antenna and its long pulse capability makes it ideal for testing essential technical and physics issues for ITER. This paper report the experimental results obtained and the technical evolution of the system since the last 'Strong Microwaves in Plasmas' workshop. The observation of a clear synergistic effect between Electron cyclotron current drive and Lower Hybrid Current Drive in fully non-inductively driven plasmas allowing a significant reduction in the Lower Hybrid power required to drive the plasma current is one of the major results of recent experiments. In another series of experiments ECCD has been exploited for studies of advanced scenarios with strongly or weakly reversed shear, resulting in high core electron temperatures and steep gradients. The operation of the system was halted for a year following a water leak in the armored water bellows feeding cooling water to the antenna mobile mirror. This incident highlighted the difficulty of cooling mobile components inside the vacuum vessel and a major modification in the mirror cooling system was implemented as a consequence. With these modifications the first test of control of the ECRH/CD injection angle in real time should proceed in the upcoming experimental campaign. (authors)

  20. Development of beam current control system in RF-knockout slow extraction

    Energy Technology Data Exchange (ETDEWEB)

    Mizushima, K., E-mail: mizshima@nirs.go.jp [Department of Accelerator and Medical Physics, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Graduate School of Science and Technology, Chiba University, Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Sato, S.; Shirai, T.; Furukawa, T.; Katagiri, K.; Takeshita, E.; Iwata, Y.; Himukai, T.; Noda, K. [Department of Accelerator and Medical Physics, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)

    2011-12-15

    A raster scanning method has been developed for cancer therapy at NIRS-HIMAC. This method requires a high-accuracy beam current control and fast beam-on/off switching. We have developed a feedback control system of the beam current with the RF-knockout slow extraction method. The system has allowed a stable response to beam-on/off switching using a feedback control delay function with a beam-current ripple of 7%.

  1. Suppression of sawtooth oscillations by lower-hybrid current drive in the ASDEX tokamak

    Science.gov (United States)

    Söldner, F. X.; McCormick, K.; Eckhartt, D.; Kornherr, M.; Leuterer, F.; Bartiromo, R.; Becker, G.; Bosch, H. S.; Brocken, H.; Derfler, H.; Eberhagen, A.; Fussmann, G.; Gehre, O.; Gernhardt, J.; Gierke, G. V.; Giuliana, A.; Glock, E.; Gruber, O.; Haas, G.; Hesse, M.; Hofmann, J.; Izvozchikov, A.; Janeschitz, G.; Karger, F.; Keilhacker, M.; Klüber, O.; Lackner, K.; Lenoci, M.; Lisitano, G.; Mast, F.; Mayer, H. M.; Meisel, D.; Mertens, V.; Müller, E. R.; Münich, M.; Murmann, H.; Niedermeyer, H.; Pietrzyk, A.; Poschenrieder, W.; Rapp, H.; Riedler, H.; Röhr, H.; Ryter, F.; Schmitter, K. H.; Schneider, F.; Setzensack, C.; Siller, G.; Smeulders, P.; Speth, E.; Steuer, K.-H.; Vien, T.; Vollmer, O.; Wagner, F.; Woyna, F. V.; Zasche, D.

    1986-09-01

    The sawtooth oscillations in tokamak discharges with Ohmic and neutral-beam heating could be suppressed when a large part of the plasma current was driven by lower-hybrid waves (IHF/Ip~=0.5). The stabilization is due to a flattening of the current profile j(r) and an increase of q(0) above 1. Higher central electron temperatures are obtained with neutral-beam heating if the sawteeth are stabilized. The increase in total energy content in this case was 30% higher than in the presence of sawteeth.

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

    International Nuclear Information System (INIS)

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

  3. An investigation of the applicability of a JxB type current drive in tokamaks

    International Nuclear Information System (INIS)

    Previous theoretical work on JxB current drives is briefly reviewed. Two separate cases are identified. The first is one in which the travelling wave propagates perpendicular to the steady state magnetic field and the second is for the situation in which propagation is parallel to a significant component of the steady state field. For the first case, field penetration and synchronous electron motion is possible. The second case is investigated by considering in detail an m=0 type mode for tokamak parameters, ion motion being taken into account. It is found that neither synchronous motion nor field penetration occurs. Since it is this latter case which is appropriate to tokamaks, these being characterised by the major current flow being parallel to the field, it is concluded that the JxB type current drive has no application in high temperature tokamak devices. (author)

  4. Oscillating field current drive and nonlinear plasma response in bootstrapped tokamaks

    International Nuclear Information System (INIS)

    The nonlinear response of bootstrapped tokamaks to oscillating field current drive (OFCD) is studied with the aid of a formal mathematical solution. The tokamak plasma response to OFCD is shown to be similar to that of a driven inductor--resistor (LR) circuit, but the effective plasma resistance can be negative. A physical picture is constructed in which the tokamak bootstrap effect is viewed as a nonlinear amplification of the plasma magnetic helicity. The bootstrap amplifier can rectify the toroidal plasma current. The importance of the tokamak thermal instability for peaking the plasma current and creating a plasma dynamo is stressed. Estimates are made which suggest that steady-state tokamak fusion reactors operating with OFCD may be achievable with moderate amplitude toroidal magnetic flux and loop voltage oscillations and oscillation driving frequencies significantly below the audible frequency range. copyright 1995 American Institute of Physics

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1994-07-01

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

  6. Modelling of RF current drive in the presence of radial diffusion

    International Nuclear Information System (INIS)

    The kinetic theory of radiofrequency current drive in tokamak plasmas is investigated. The problem of the impact of anomalous transport on the driven current profile and efficiency is considered in detail. Among the possible candidates for explaining anomalous transport in tokamaks, magnetic turbulence is known to have a strong influence on the dynamics of superthermal electrons and is assumed here to be the basic mechanism responsible for radial diffusion of the rf-driven. The 3-dimensional kinetic equation in the presence of rf heating and magnetic turbulence is studied. Its properties are first investigated by a non-local response function technique. Both the adjoint formalism and the Langevin equations method are extended to the case of radially diffusing electrons. The full kinetic equation is numerically solved by means of a 3-D Fokker-Planck code. Applications to lower-hybrid current drive are presented and several kinetic effects are discussed

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

    International Nuclear Information System (INIS)

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

  8. Electron cyclotron current drive and m=2 mode stabilization in NET

    International Nuclear Information System (INIS)

    Current drive by electron cyclotron waves (ECCD) in the Next European Torus is investigated. The profile and the efficiency of the driven current are calculated with a 3-dimensional bounce averaged Fokker-Placnk code coupled to a toroidal ray-tracing code. This study consists of two parts. In the first part the application of EC waves to drive the central part of the main plasma current for steady state operation is studied. It is shown taht the highest current drive efficiencies are obtained using the ordinary wave at up-shifted frequency (ω > ωc. The maximum obtainable efficiency is limited by overlap with the second harmonic resonance and is given by η∼0.3AW-1 102Om-2. Off-axis, this efficiency is reduced by a factor of 2 due to trapped particles. In the second part, the application of ECCD for control of the current profile around the q=2 surface to prevent growth of the m=2, n=1 tearing mode is studied. In all cases studied, the injection of 10 MW of EC wave power at the appropriate frequency and injection angle is sufficient to stabilize the m=2, n=1 tearing mode. (author). 11 refs.; 5 figs.; 2 tabs

  9. Electric Circuit Model Suitable for Common Mode Current Paths Distributing in the Motor Drive System

    Science.gov (United States)

    Mutoh, Nobuyoshi; Ogata, Mitsukatsu; Harashima, Fumio

    Experimental date are used to analyze conducted EMI noises which are produced in a motor drive system with power converters comprised of a converter and an inverter. The processes are investigated in which common mode noises (voltages and currents) are strongly influenced by voltage fluctuations occurring due to switching operations. It is found that the common mode currents are resonance currents which appear in series resonance circuits distributed in the motor drive system. The circuits have various kinds of resonance frequencies related to voltage fluctuations produced by switching operations and micro-surge voltages generated at the terminal of machines such as an ac rector or a motor. Thus, parameters of the distributed series resonance circuits are estimated using the transient waveforms obtained by separating the common mode current into waves analyzed by the FFT method. It is proved through simulations and experiments that the proposed circuit models closely represent actual electric circuits for common mode current paths distributed in the motor drive system.

  10. Current drive experiments in the helicity injected torus (HIT-II)

    International Nuclear Information System (INIS)

    The Helicity Injected Torus [HIT-II: T. Jarboe et al., Phys. Plasmas 5, 1807 (1998)] is a low-aspect-ratio tokamak capable of both inductive (ohmic) and Coaxial Helicity Injection (CHI) current drive. HIT-II is modest in size (major radius R=0.3 m, minor radius a=0.2 m, and on-axis toroidal field of up to 0.5 T), but has demonstrated 200 kA of toroidal plasma current, using either CHI or induction separately. The loop voltage, boundary flux, and plasma equilibrium are controlled by a real-time flux feedback system. HIT-II ohmic plasmas exhibit reconnection events during both the current ramp-up and decay, events that relax the current profile while conserving the magnetic helicity. A new operating regime for CHI plasmas, using a double-null divertor (DND) boundary flux, has been explored. DND CHI plasmas exhibit good shot-to-shot reproducibility, low impurity content, minimal shorting current in the absorber region, and EFIT-reconstructed equilibria consistent with significant closed-flux core regions [EFIT: L. Lao et al., Nucl. Fusion 25, 1611 (1985)]. HIT-II DND CHI discharges also exhibit a continuous n=1 mode at the outer midplane, a mode that has been correlated experimentally with current-profile relaxation. A detailed explanation of helicity injection current drive has been developed, which is consistent with experimental observations of HIT and HIT-II discharges. According to this mechanism, asymmetric distortion of the n=1 mode structure generates current drive in the core plasma by dynamo action, relaxing the CHI-driven current profile

  11. Impact of beam smoothing method on direct drive target performance for the NIF

    International Nuclear Information System (INIS)

    The impact of smoothing method on the performance of a direct drive target is modeled and examined in terms of its l-mode spectrum. In particular, two classes of smoothing methods are compared, smoothing by spectral dispersion (SSD) and the induced spatial incoherence (ISI) method. It is found that SSD using sinusoidal phase modulation (FM) results in poor smoothing at low l-modes and therefore inferior target performance at both peak velocity and ignition. Modeling of the hydrodynamic nonlinearity shows that saturation tends to reduce the difference between target performance for the smoothing methods considered. However, using SSD with more generalized phase modulation results in a smoothed spatial spectrum, and therefore target performance, which is identical to that obtained with the ISI or similar method where random phase plates are present in both methods and identical beam divergence is assumed

  12. Production and maintenance of high poloidal beta tokamak plasmas by means of rf current drive

    Energy Technology Data Exchange (ETDEWEB)

    Luckhardt, S.C.; Chen, K.; Coda, S.; Kesner, J.; Kirkwood, R.; Lane, B.; Porkolab, M.; Squire, J.

    1989-03-27

    It is shown that in tokamak plasmas sustained by rf current drive, the contribution of the suprathermal rf-driven electron population to the poloidal beta (..beta../sub p/) can be substantial if the total current is comparable to the Alfven critical current, I/sub A/ = (4..pi..mcv/..mu../sub 0/ec)..gamma... Equilibria with values of epsilon..beta../sub p/ up to approximately 1.3 were obtained, and no equilibrium or gross stability limits were observed.

  13. Current Reversal Due to Coupling Between Asymmetrical Driving Force and Ratchet Potential

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Transport of a Brownian particle moving in a periodic potential is investigated in the presence of an asymmetric unbiased external force. The asymmetry of the external force and the asymmetry of the potential are the two ways of inducing a net current. It is found that the competition of the spatial asymmetry of potential with the temporal asymmetry of the external force leads to the phenomena like current reversal. The competition between the two opposite driving factors is a necessary but not a sufficient condition for current reversals.

  14. Closure of the single fluid magnetohydrodynamic equations in presence of electron cyclotron current drive

    OpenAIRE

    Westerhof E.; Pratt J.; Ayten B.

    2015-01-01

    In the presence of electron cyclotron current drive (ECCD), the Ohm’s law of single fluid magnetohydrodynamics (MHD) is modified as E + v × B = η(J – JECCD). This paper presents a new closure relation for the EC driven current density appearing in this modified Ohm’s law. The new relation faithfully represents the nonlocal character of the EC driven current and its main origin in the Fisch-Boozer effect. The closure relation is validated on both an analytical solution of an approximated Fokke...

  15. Closure of the single fluid magnetohydrodynamic equations in presence of electron cyclotron current drive

    Science.gov (United States)

    Westerhof, E.; Pratt, J.; Ayten, B.

    2015-03-01

    In the presence of electron cyclotron current drive (ECCD), the Ohm's law of single fluid magnetohydrodynamics (MHD) is modified as E + v × B = η(J - JECCD). This paper presents a new closure relation for the EC driven current density appearing in this modified Ohm's law. The new relation faithfully represents the nonlocal character of the EC driven current and its main origin in the Fisch-Boozer effect. The closure relation is validated on both an analytical solution of an approximated Fokker-Planck equation as well as on full bounce-averaged, quasi-linear Fokker-Planck code simulations of ECCD inside rotating magnetic islands.

  16. High-harmonic ion cyclotron heating and current drive in ultra-small aspect ratio tokamaks

    International Nuclear Information System (INIS)

    Ultra-small aspect ratio tokamaks present a totally new plasma environment for heating and current drive experiments and involve a number of physics issues that have not previously been explored. These devices operate at low magnetic field and relatively high density so that the effective dielectric constant of the plasma to high harmonic fast waves (HHFW), is quite high, and perpendicular wavelength of fast waves is very short. λ ∼ 2.0 cm compared with λ - 10-20 cm. This makes possible strong electron absorption at high harmonics of the ion cyclotron frequency, Ωi, and at fairly high phase velocity in relation to electron thermal velocity. If the antenna system can control the parallel wave spectrum, this offers the promise of high efficiency off-axis current drive and the possibility for current drive radial profile control. Antenna phasing is ineffective for profile control in conventional tokamaks because of central absorption. There are also challenges for antenna design in this regime because of the high dielectric constant and the large angle of the magnetic field with respect to the equatorial plane (∼45 degrees), which varies greatly during current ramp. Preliminary experiments in this HHFW regime are being carried out in CDX-U

  17. Lower hybrid experiments at the 1 MW level on Alcator C: heating and current drive

    International Nuclear Information System (INIS)

    Lower hybrid current drive and heating experiments have been carried out on the Alcator C tokamak at power levels up to 1.15 MW in the density range 1.0 x 1013 less than or equal to anti n/sub e/(cm-3) less than or equal to 1.0 x 1014. By launching waves with 670, 900 or 1120 phasing of adjacent waveguides, maximum flat-top current drive efficiencies of eta = R(m) x n(1014cm-3)I(MA)/P(MW) = 0.12 at B = 10 tesla, and eta approx. = 0.08 at B = 8 tesla were obtained with molybdenum limiters. With graphite, or silicon-carbide coated graphite limiters the efficiencies were 30 to 40% lower. Current ramping experiments have also been carried out at densities up to anti n approx. = 6 x 1013cm-3. By phasing the adjacent waveguides at 1800, heating experiments were performed in the density range 8 x 1013 less than or equal to anti n(cm-3) less than or equal to 2 x 1014 in both hydrogen and deuterium plasmas. This range of densities corresponds to the electron Landau heating mode. Using molybdenum limiters, typical heating rates of the order of eta/sub H/ = delta Σ n/sub j/T/sub j//P/sub rf/ approx. = 10 eV/kW 1013cm-3 were obtained, whereas with the SiC coated graphite limiters heating rates up to eta/sub H/ approx. = 22 were achieved. Measurements of soft and hard x-rays indicate the presence of substantial electron tails in both the current drive and the electron heating regimes. A combined transport, ray-tracing and Fokker-Planck code is used to analyze and model both the heating and the current drive results

  18. An accurate low current measurement circuit for heavy iron beam current monitor

    International Nuclear Information System (INIS)

    Heavy-ion beams at 106 particles per second have been applied to the treatment of deep-seated inoperable tumors in the therapy terminal of the Heavy Ion Research Facility in Lanzhou (HIRFL) which is located at the Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS). An accurate low current measurement circuit following a Faraday cup was developed to monitor the beam current at pA range. The circuit consisted of a picoammeter with a bandwidth of 1 kHz and a gated integrator (GI). A low input bias current precision amplifier and new guarding and shielding techniques were used in the picoammeter circuit which allowed as to measure current less than 1 pA with a current gain of 0.22 V/pA and noise less than 10 fA. This paper will also describe a novel compensation approach which reduced the charge injection from switches in the GI to 10−18 C, and a T-switch configuration which was used to eliminate leakage current in the reset switch.

  19. Feedback stabilization of magnetic islands by rf heating and current drive

    International Nuclear Information System (INIS)

    Feedback stabilization of the m = 2 mode in tokamaks would be advantageous for disruption-free operation at low q-values. Stabilization of the m = 1 mode and resulting ''sawteeth'' could lead to substantial increases in the stable β-value, as well as indirect stabilization of the m = 2 mode, by permitting q(0)-values below unity. Stabilization of these modes at acceptable amplitudes appears possible by feedback-modulated heating or current drive applied to the region within the mode-induced magnetic islands. Current drive offers by far the more efficient mechanism, and it can be accomplished using lower-hybrid or electron-cyclotron radio-frequency (rf) techniques. For the lower-hybrid case, ray-tracing calculations demonstrate the needed localization of the rf power, despite long ray paths in the toroidal direction. Top-launched lower-hybrid waves are favored for localized absorption

  20. Design of Current Controller for Two Quadrant DC Motor Drive by Using Model Order Reduction Technique

    CERN Document Server

    Ramesh, K; Nirmalkumar, A; Gurusamy, G

    2010-01-01

    In this paper, design of current controller for a two quadrant DC motor drive was proposed with the help of model order reduction technique. The calculation of current controller gain with some approximations in the conventional design process is replaced by proposed model order reduction method. The model order reduction technique proposed in this paper gives the better controller gain value for the DC motor drive. The proposed model order reduction method is a mixed method, where the numerator polynomial of reduced order model is obtained by using stability equation method and the denominator polynomial is obtained by using some approximation technique preceded in this paper. The designed controllers responses were simulated with the help of MATLAB to show the validity of the proposed method.

  1. The effect of ion motion on rotating magnetic field current drive

    International Nuclear Information System (INIS)

    The effect of ion motion on rotating magnetic field (RMF) current drive in field reversed configurations is studied using a fully two-dimensional numerical code that solves the two fluid equations with massless electrons and constant uniform temperature. The ion momentum equation includes viscosity and collisions with neutrals, which remain fixed. The electrons are described with an Ohm's law that includes the Hall and pressure gradient terms. For full penetration of the RMF, ion spin-up due to collisions with electrons reduces the current drive efficiency and a large fraction of neutrals is needed to prevent the ions from acquiring high azimuthal velocities. For conditions that would result in incomplete penetration with the fixed ion model, ion rotation and variable density can facilitate the penetration of the RMF, thus increasing the efficiency. The rotation modifies the density profile and can trigger rotational instabilities

  2. FED-A, an advanced performance FED based on low safety factor and current drive

    International Nuclear Information System (INIS)

    The FED-A study aims to quantify the potential improvement in cost-effectiveness of the Fusion Engineering Device (FED) by assuming low safety factor q (less than 2 as opposed to about 3) at the plasma edge and noninductive current drive (as opposed to only inductive current drive). The FED-A performance objectives are set to be : (1) ignition assuming International Tokamak Reactor (INTOR) plamsa confinement scaling, but still achieving a fusion power amplification Q greater than or equal to 5 when the confinement is degraded by a factor of 2; (2) neutron wall loading of about 1 MW/m2, with 0.5 MW/m2 as a conservative lower bound; and (3) more clearly power-reactor-like operations, such as steady state

  3. Particle confinement improvement during 2. 45 GHz lower-hybrid current-drive experiments

    Energy Technology Data Exchange (ETDEWEB)

    Mayberry, M.J.; Chen, K.; Luckhardt, S.C.; Porkolab, M.

    1987-07-01

    Particle confinement behavior during 2.45 GHz lower-hybrid current drive has been investigated on the Versator II tokamak (Phys. Fluids 29, 1985 (1986)). It is found that during combined Ohmic and rf current drive the global particle confinement time tau/sub p/ increases by up to a factor of 2 compared to purely Ohmically driven discharges, as observed in earlier 800 MHz experiments at lower densities n-bar/sub e/ less than or equal to6 x 10/sup 12/ cm/sup -3/. In the present experiments, tau/sub p/ increases have been observed at densities up to n-bar/sub e/ = 2 x 10/sup 13/ cm/sup -3/.

  4. Transformer recharge by lower hybrid current drive on HT-7 superconducting tokamak

    International Nuclear Information System (INIS)

    The results of transformer recharging experiments by means of lower hybrid current drive (LHCD) on HT-7 superconducting Tokamak are summarized and analyzed on the basis of a simple transformer circuit. A steady-state plasma can be maintained at about 50 kA by LHCD while the primary coils of Tokamak transformer is recharged. During the recharge phase, a constant plasma loop voltage about -0.05 V keeps for about 1.0 s and the magnetic flux of the Tokamak transformer changes from 0.645 to 0.615 Vs. A maximum recharging efficiency of 1.25% has been obtained at a line averaged electron density of 0.5 x 1019 m-3. In addition, full non-inductive current drive experiment has been realized on HT-7 Tokamak

  5. A relativistic model of electron cyclotron current drive efficiency in tokamak plasmas

    Directory of Open Access Journals (Sweden)

    Lin-Liu Y.R.

    2012-09-01

    Full Text Available A fully relativistic model of electron cyclotron current drive (ECCD efficiency based on the adjoint function techniques is considered. Numerical calculations of the current drive efficiency in a tokamak by using the variational approach are performed. A fully relativistic extension of the variational principle with the modified basis functions for the Spitzer function with momentum conservation in the electron-electron collision is described in general tokamak geometry. The model developed has generalized that of Marushchenko’s (N.B . Marushchenko, et al. Fusion Sci. & Tech., 2009, which is extended for arbitrary temperatures and covers exactly the asymptotic for u ≫ 1 when Z → ∞, and suitable for ray-tracing calculations.

  6. FED-A, an advanced performance FED based on low safety factor and current drive

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Y.K.M.; Rutherford, P.H.

    1983-08-01

    The FED-A study aims to quantify the potential improvement in cost-effectiveness of the Fusion Engineering Device (FED) by assuming low safety factor q (less than 2 as opposed to about 3) at the plasma edge and noninductive current drive (as opposed to only inductive current drive). The FED-A performance objectives are set to be : (1) ignition assuming International Tokamak Reactor (INTOR) plamsa confinement scaling, but still achieving a fusion power amplification Q greater than or equal to 5 when the confinement is degraded by a factor of 2; (2) neutron wall loading of about 1 MW/m/sup 2/, with 0.5 MW/m/sup 2/ as a conservative lower bound; and (3) more clearly power-reactor-like operations, such as steady state.

  7. Coupling of alpha-channeling to parallel wavenumber upshift in lower hybrid current drive

    CERN Document Server

    Ochs, Ian E; Fisch, Nat J

    2014-01-01

    Although lower hybrid waves have been shown to be effective in driving plasma current in present-day tokamaks, they are predicted to strongly interact with the energetic alpha particles born from fusion reactions in eventual tokamak reactors. In the presence of the expected strong alpha particle birth gradient, however, this interaction can produce wave amplification rather than wave damping, but only if the launch position and orientation of the waveguides are suitably arranged. The flexibilities in achieving the amplification effect are identified through a consideration of symmetries in the channeling effect, in the wave propagation, and in the tokamak field configuration. Interestingly, for current drive that supports the poloidal magnetic field, the achievement of wave amplification through alpha channeling is fundamentally coupled to effects leading to the elusive parallel wavenumber upshift.

  8. Study and Experimental Characterization of a Novel Photo Injector for the CLIC Drive Beam

    CERN Document Server

    Mete, Oznur; Rivkin, Leonid

    2011-01-01

    Abstract In this thesis, the transverse and longitudinal beam properties of the PHIN photoinjector are characterized. The ob jective of the research is to demonstrate the reliable and stable production of a 1.3 µs long bunch train, with 2.33 nC charge per bunch and 4.5 µC of total charge, by the PHIN photoinjector. The results of this thesis are the important steps towards the feasibility demonstration of a photoinjector as the Compact Linear Collider’s drive beam source. The PHIN photoinjector has been conceptualized by a collaboration between “Laboratoire de l’Accélérateur Linéaire (LAL)”, “Rutherford Appleton Laboratory (RAL)” and “Organisation Européenne pour la Recherche Nucléaire (CERN)”. Within this collaboration, LAL and RAL have committed to the design and the construction of the RF gun and laser, respectively. The photocathode production as well as the overall coordination and commissioning were under the responsibility of CERN. The pro ject is in the framework of the second...

  9. Direct-drive, hollow-shell implosion studies on the 60-beam, UV OMEGA laser system

    International Nuclear Information System (INIS)

    Direct-drive implosion experiments have been performed on the University of Rochester's 60-beam, 30 kJ, UV (351 nm) OMEGA [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] laser system to investigate the conditions at maximum compression of polymer-shell targets with zero- or low-pressure (≤3 atm) gas fills. By using deuterium-bearing shells (CD), the imploded-core conditions have been diagnosed with both x-ray and neutron spectral measurements. The core electron temperature (kTe) and shell areal density (ρRshell) are determined from the emergent x-ray spectrum, while independent inferences of ρRshell are obtained from the measured primary (DD) and secondary (DT) neutron yields. Target performance was investigated for a range of beam-smoothing conditions [none to 0.25 THz-bandwidth smoothing by spectral dispersion along two dimensions (2-D SSD)] and a set of pulse shapes (1 ns square pulse to a 2.5 ns pulse with a 1:40 foot-to-main-pulse power ratio). The results have conclusively demonstrated the ability to compress targets to shell areal densities in the range of ∼60 to 130 mg/cm2. (c) 2000 American Institute of Physics

  10. Fast electron dynamics in lower hybrid current drive experiment on HT-7 tokamak

    Institute of Scientific and Technical Information of China (English)

    Shi Yue-Jiang; Kuang Gang-Li; Li Jian-Gang; HT-7 Team; Wan Bao-Nian; Chen Zhong-Yong; Hu Li-Qun; Lin Shi-Yao; Ruan Huai-Lin; Qian Jin-Ping; Zhen Xiang-Jun; Ding Bo-Jiang

    2005-01-01

    The dynamic behaviour of fast electron in lower hybrid current drive (LHCD) experiments is a crucial issue in the sense of enhancing plasma performance. A new hard x-ray diagnostic system on HT-7 allows the investigation of the lower hybrid wave dynamics. The behaviour of fast electron is studied in several kinds of LHCD experiments, including long pulse discharges, high performance discharges and counter-LHCD experiments.

  11. Recent Advances in the long pulse heating and current drive system for KSTAR

    International Nuclear Information System (INIS)

    The heating and current-drive systems of KSTAR tokamak have been developed to support long pulse, high β, advanced tokamak physics experiments. Key technologies relevant for high power and long-pulse operation are under development. Substantial progresses have been made in areas such as ion source, RF launchers, tuning components and high power supplies and they will make the advanced tokamak operation of the KSTAR be obtainable and maintained for long-pulse operating condition. (author)

  12. Design of ITER-FEAT RF heating and current drive systems

    International Nuclear Information System (INIS)

    Three radio frequency (RF) heating and current drive (H and CD) systems are being designed for ITER-FEAT: an electron cyclotron (EC), an ion cyclotron (IC) and a lower hybrid (LH) System. The launchers of the RF systems use four ITER equatorial ports and are fully interchangeable. They feature equal power outputs (20 MW/port), similar neutron shielding performance, and identical interfaces with the other machine components. An outline of the design is given in the paper. (author)

  13. Theoretical studies of lower hybrid current drive and ion-cyclotron heating in tokamaks

    International Nuclear Information System (INIS)

    A computational model for PLT lower hybrid current drive and ramp-up experiments combines a parallel velocity Fokker-Planck treatment of lower hybrid current drive with minor radius flux diffusion and toroidal ray-tracing wave propagation. Computational and experimental results are in good accord. Analytic solutions of the two-dimensional velocity space (v/sub perpendicular/, v/sub parallel/) diffusion problem give values of the current drive parameter J/P/sub d/ which agree with numerical results, both relativistically and nonrelativistically. Turning to ICRF heating, two new all-metal antenna designs will permit power flux up to 10 kW/cm2. A full wave solution to the magnetosonic wave equation, based on the parabolic method, yields cylindrical convergence and treats the diffraction limitation on intensity correctly. Mode conversion with energy absorption has been added to the BALDUR ICRF modeling code. A Fokker-Planck treatment of high energy ion tail formation by ICRF finds that enhanced thermonuclear reactivity can occur

  14. High harmonics radiation, related power loss and passive current drive in tokamaks

    International Nuclear Information System (INIS)

    Emission of weakly damped high harmonics radiation, the related synchrotron power loss and passive current drive in tokamaks with a fish-scale first wall are investigated. Firstly, the properties of overlapping harmonics are discussed using general analytical formulas and numerical applications. Next, the radiation power loss and efficiency of passive current drive in tokamak reactors are derived for the asymmetric fish-scale first wall. It is shown that the radiation power loss is determined by the direction-averaged reflection coefficient σ0 and the passive current drive by the differential reflectivity Δσ/(1-σ0). Finally, the problem of experimental investigations of the high harmonics radiation spectra, of σ0 and Δσ/(1-σ0) in existing and next-step tokamaks is discussed. It is shown that accurate measurements of the radiation spectra and the fish-scale reflectivity can be performed at arbitrary electron temperature using a partial fish-scale structure located near the tokamak equatorial plane. (author)

  15. Electron Cyclotron Radiation, Related Power Loss, and Passive Current Drive in Tokamaks: A Review

    International Nuclear Information System (INIS)

    A critical review on emission of weakly damped, high-harmonics electron cyclotron radiation, the related synchrotron power loss, and passive current drive in tokamaks with a fish-scale first wall is presented. First, the properties of overlapping harmonics are discussed using general analytical formulas and numerical applications. Next, the radiation power loss and efficiency of passive current drive in tokamak reactors are derived for the asymmetric fish-scale first wall. The radiation power loss is determined by the direction-averaged reflection coefficient σ0 and the passive current drive by the differential reflectivity δσ/(1 - σ0). Finally, the problem of experimental investigations of the high harmonics radiation spectra, of σ0 and δσ/(1 - σ0) in existing and next-step tokamaks, is discussed. Accurate measurements of the radiation spectra and the fish-scale reflectivity can be performed at arbitrary electron temperature using a partial fish-scale structure located near the tokamak equatorial plane

  16. First principles fluid modelling of magnetic island stabilization by electron cyclotron current drive (ECCD)

    Science.gov (United States)

    Février, O.; Maget, P.; Lütjens, H.; Luciani, J. F.; Decker, J.; Giruzzi, G.; Reich, M.; Beyer, P.; Lazzaro, E.; Nowak, S.; the ASDEX Upgrade Team

    2016-04-01

    Tearing modes are MagnetoHydroDynamics (MHD) instabilities that reduce the performance of fusion devices. They can however be controlled and suppressed using electron cyclotron current drive (ECCD) as demonstrated in various tokamaks. In this work, simulations of island stabilization by ECCD-driven current have been carried out using the toroidal nonlinear 3D full MHD code xtor-2f, in which a current source term modeling the ECCD has been implemented. The efficiency parameter, {η\\text{RF}} , has been computed and its variations with respect to source width and location were also computed. The influence of parameters such as current intensity, source width and position with respect to the island was evaluated and compared to the modified Rutherford equation. We retrieved a good agreement between the simulations and the analytical predictions concerning the variations of control efficiency with source width and position. We also show that the 3D nature of the current source term can lead to the onset of an island if the source term is precisely applied on a rational surface. We report the observation of a flip phenomenon in which the O- and X-points of the island rapidly switch their position in order for the island to take advantage of the current drive to grow.

  17. Leakage current and commutation losses reduction in electric drives for Hybrid Electric Vehicle

    Science.gov (United States)

    Miliani, El Hadj

    2014-06-01

    Nowadays, leakage current and inverter losses, produced by adjustable-speed AC drive systems become one of the main interested subject for researchers on Electric Vehicle (EV) and Hybrid Electric Vehicle (HEV) technology. The continuous advancements in solid state device engineering have considerably minimized the switching transients for power switches but the high dv/dt and high switching frequency have caused many adverse effects such as shaft voltage, bearing current, leakage current and electromagnetic interference (EMI). The major objective of this paper is to investigate and suppress of the adverse effects of a PWM inverter feeding AC motor in EV and HEV. A technique to simultaneously reduce the leakage current and the switching losses is presented in this paper. Based on a discontinuous space vector pulse width modulation (DSVPWM) and a modular switches gate resistance, inverter losses and leakage current are reduced. Algorithms are presented and implemented on a DSP controller and experimental results are presented.

  18. Load Torque Compensator for Model Predictive Direct Current Control in High Power PMSM Drive Systems

    DEFF Research Database (Denmark)

    Preindl, Matthias; Schaltz, Erik

    2010-01-01

    In drive systems the most used control structure is the cascade control with an inner torque, i.e. current and an outer speed control loop. The fairly small converter switching frequency in high power applications, e.g. wind turbines lead to modest speed control performance. An improvement bring...... dynamic behaviour. It compensates the load torque influence on the speed control setting a feed forward torque value, i.e. current reference value. The benefits are twice. The speed controller reaches immediately the speed reference value avoiding offsets which must be compensated by the weak integrator...

  19. Recent progress on lower hybrid current drive and implications for ITER

    CERN Document Server

    Hillairet, Julien; Goniche, M; Achard, J; Armitano, A; Beckett, B; Belo, J; Berger-By, G; Corbel, E; Delpech, L; Decker, J; Dumont, R; Guilhem, D; Kazarian, F; Litaudon, X; Magne, R; Marfisi, L; Mollard, P; Namkung, W; Nilsson, E; Park, S; Peysson, Y; Preynas, M; Sharma, P K; Prou, M

    2015-01-01

    The sustainment of steady-state plasmas in tokamaks requires efficient current drive systems. Lower Hybrid Current Drive (LHCD) is currently the most efficient method to generate a continuous additional off-axis toroidal plasma current as well as reduce the poloidal flux consumption during the plasma current ramp-up phase. The operation of the Tore Supra ITER-like LH launcher has demonstrated the capability to couple LH power at ITER-like power densities with very low reflected power during long pulses. In addition, the installation of eight 700kW/CW klystrons at the LH transmitter has allowed increasing the total LH power in long pulse scenarios. However, in order to achieve pure stationary LH sustained plasmas, some R\\&D are needed to increase the reliability of all the systems and codes, from the RF sources to the plasma scenario prediction. The CEA/IRFM is addressing some of these issues by leading a R\\&D program towards an ITER LH system and by the validation of an integrated LH modeling suite of...

  20. Effect of finite beam width on current separation in beam plasma system: Particle-in-Cell simulations

    CERN Document Server

    Shukla, Chandrasekhar; Patel, Kartik

    2015-01-01

    The electron beam propagation in a plasma medium is susceptible to several instabilities. In the relativistic regime typically the weibel instability leading to the current separation dominates. The linear instability analysis is carried out for a system wherein the transverse extent of the beam is infinite. Even in simulations, infinite transverse extent of the beam has been chosen. In real situations, however, beam width will always be finite. keeping this in view the role of finite beam width on the evolution of the beam plasma system has been studied here using Particle - in - Cell simulations. It is observed that the current separation between the forward and return shielding current for a beam with finite beam occurs at the scale length of the beam width itself. Consequently the magnetic field structures that form have maximum power at the scale length of the beam width. This behaviour is distinct from what happens with a beam with having an infinite extent represented by simulations in a periodic box, ...

  1. Predictive Pulse Pattern Current Modulation Scheme for Harmonic Reduction in Three-Phase Multi-Drive Systems

    DEFF Research Database (Denmark)

    Davari, Pooya; Yang, Yongheng; Zare, Firuz;

    2016-01-01

    The majority of the industrial motor drive systems are equipped with the conventional line-commutated front-end rectifiers, and being one of the main sources of harmonics in the power line. While a parallel combination of these drive units elevates current quality issues, a proper arrangement of...... them can lead to the cancellation of specific harmonics. This paper proposes a new cost-effective harmonic mitigation solution for multi-drive systems using a predictive pulse pattern current modulation control strategy. The proposed technique applies suitable interaction among parallel drive units at...

  2. Progress in internal transport barrier plasmas with lower hybrid current drive and heating in JET (Joint European Torus)

    International Nuclear Information System (INIS)

    In optimized shear plasmas in the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)], safety factor (q) profiles with negative magnetic shear are produced by applying lower hybrid (LH) waves during the plasma current ramp-up phase. These plasmas produce a barrier to the electron energy transport. The radius at which the barrier is located increases with the LH wave power. When heated with high power from ion cyclotron resonance heating and neutral beam injection, they can additionally produce transient internal transport barriers (ITBs) seen on the ion temperature, electron density, and toroidal rotation velocity profiles. Due to recent improvements in coupling, q profile control with LH current drive in ITB plasmas with strong combined heating can be explored. These new experiments have led to ITBs sustained for several seconds by the LH wave. Simulations show that the current driven by the LH waves peaks at the ITB location, indicating that it can act in the region of low magnetic shear

  3. Low-energy High-current Electron Beam Generation in Plasma System and Beam-Plasma Interaction

    International Nuclear Information System (INIS)

    The review of results of experimental investigations and computer simulations of low-energy high-current electron beam generation in a low-impedance system and dynamics of beam-plasma system are given. The system includes a long plasma-filled diode, an auxiliary thermionic cathode and an explosive emission cathode. The auxiliary cathode is used to generate the a low-current, low-voltage electron beam to form long plasma anode by means of a residual gas ionisation in an external longitudinal magnetic field. The high-current low-energy electron beam is generated from the explosive emission cathode embedded in preliminary prepared plasma. Peculiarities of the system are due to: 1) the generation of electron beams with currents exceeding Alfven's limit; 2) the charge density of the beam close to the plasma density. These peculiarities complicate beam-plasma interaction significantly due to sharp non-uniform distribution of the beam current density, dominant transverse motion of the beam electrons and redistribution of ion-plasma density under the influence of fields. Computer simulation was performed using electromagnetic PIC code KARAT for different geometry's of the system

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

    Science.gov (United States)

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

    2015-11-01

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

  5. Lower hybrid current drive: an overview of simulation models, benchmarking with experiment, and predictions for future devices

    International Nuclear Information System (INIS)

    This paper reviews the status of lower hybrid current drive (LHCD) simulation and modeling. We first discuss modules used for wave propagation, absorption, and current drive with particular emphasis placed on comparing exact numerical solutions of the Fokker Planck equation in 2-dimension with solution methods that employ 1-dimensional and adjoint approaches. We also survey model predictions for LHCD in past and present experiments showing detailed comparisons between simulated and observed current drive efficiencies and hard X-ray profiles. Finally we discuss several model predictions for lower hybrid current profile control in proposed next step reactor options. (authors)

  6. ECW/EBW heating and current drive experiment results and prospects for CW operation in QUEST

    International Nuclear Information System (INIS)

    A CW phased-array antenna system for electron cyclotron/Bernstein wave heating and current drive (ECWH/CD, EBWH/CD) experiments was developed in the QUEST. The antenna was designed to excite an elliptically polarized pure O-mode wave in oblique injection for the O-X-B mode conversion scenario, and its good performance was confirmed at a high power level. Long pulse discharges with a plasma current of 10 kA and 15 kA were non-inductively attained for 37 s and 20 s, respectively, with only radio frequency (RF) power. Divertor configurations were also obtained in the RF-sustained plasmas. A new operational window for sustained plasma current was observed in the high-density plasma with a higher RF incident power. Two new heating and current drive systems with an 8.56 GHz klystron and a 28 GHz gyrotron are being prepared to conduct CW EBWH/CD experiments in the high-density plasma. (author)

  7. A Modified Bridgeless Converter for SRM Drive with Reduced Ripple Current

    Directory of Open Access Journals (Sweden)

    Maheswari C krishnakumar

    2015-06-01

    Full Text Available Single Phase Switched Reluctance Motor is more popular in many industrial purposes for high speed applications because of its robust and rugged construction. For low cost and variable speed drive applications SRM are widely used.Due to doubly salient structure of motor, the torque pulsations are high when compared to other sinusoidal machines. The major drawback in using SRM drive is torque pulsations and increased number of switching components. In order to overcome these drawbacks, a bridgeless Single Ended Primary Inductor Converter (SEPIC is proposed. The major advantages of this converter are continuous output current,smaller voltage ripple and reduced semiconductor current stress when compared to the conventional SEPIC converter. The ripple free input current is obtained by using additional winding of input inductor and auxiliary capacitors. To achieve high efficiency, active power factor correction circuits (PFC are employed to precise the power factor. Further, the unity power factor can be obtained by making the input current during switching period proportional to the input voltage is proposed. The proposed system consists of reduced components and it is also capable of reducing the conduction losses. The working principles and the waveforms of proposed converter are analyzed. To analyze the circuit operation, theoretical analysis and simulation results are provided. Finally, the  comparison between the waveforms of conventional SEPIC and proposed system is presented by using MATLAB/Simulink tools.

  8. Numerical studies of electron cyclotron wave current drive on HL-2A tokamak

    International Nuclear Information System (INIS)

    The electron cyclotron wave (ECW) current drive (CD) for the HL-2A tokamak is investigated numerically with a new ray-tracing and Fokker-Planck code. The code is benchmarked with other well-tested linear and quasilinear codes and is then used to study the electron cyclotron current drive on the HL-2A tokamak. The wave propagation, power deposition, and driven-current profiles are presented. The effect of electron trapping is also assessed. It is found that quasilinear effects are negligible at the present ECW power levels and that when both waves are injected at an angle of 20° on the plasma equatorial plane, the CD efficiency for the HL-2A saturates at ∼0.029 × 1020 A/W/m2 and ∼0.020 × 1020 A/W/m2 for the 0.5 MW/68 GHz first harmonic ordinary (O1) and 1 MW/140 GHz second harmonic extraordinary (X2) modes, respectively. The effects of the plasma density, temperature, and wave-launching position on the driven current are also investigated analytically and numerically

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

    Science.gov (United States)

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

    2009-02-01

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

  10. Electro-static beam steering mechanism for a high current negative ion beam consisting of multi-beamlets

    International Nuclear Information System (INIS)

    An electrostatic beam steering mechanism (ESM) has been designed and tested to deflect negative ion beams consisting of multi-beamlets. A steering angle of 10 mrad was obtained within the deviation of less than 1 mrad by biasing two electrodes at 0.5 kV and -0.75 kV for 120 keV H- ion beam. The current flowing to the positive electrode was no more than 10% of the beam current at a pressure of 2.8x10-5 Torr. (author)

  11. Development of a highly sensitive beam current monitor with a SQUID and superconducting magnetic shield

    International Nuclear Information System (INIS)

    Beam diagnostics are an essential constituent of any accelerator. There are a large variety of beam parameters, and total current is one of the most important parameters for accelerators. A current monitor is used to operate an accelerator efficiently and to improve the performance of the machine. A Faraday cup is the most fundamental current detection process, in which charged particles are stopped in the cup. However, this destructive method cannot be applied for high-current or high-energy beams because the total energy carried by the beam can destroy and activate the intercepting material. Therefore, non-destructive beam current measurement requires the use of current transformers that detect the magnetic field produced by the pulsed or DC beam. On the other hand, a new type of beam current monitor using a low-temperature superconducting (LTS) magnetic shield and an LTS SQUID was developed to measure the faint ion beams that are below the lowest measurable limit of the DC current transformer (DCCT) for atomic-physics studies. Recently, a prototype of a highly sensitive SQUID current monitor for measuring the intensity of faint beams, such as radioisotope beams, was completed for the RIKEN RI beam factory. This monitor is composed of a high-temperature superconducting (HTS) magnetic shield and an HTS SQUID. The first measurements using ion beams were carried out in the CNS experimental hall and RIKEN Ring Cyclotron (RRC). This paper first describes the principle of the conventional current monitor such as the Faraday cup and current transformers. Second, the progress of the LTS SQUID current monitor is discussed, and finally, the present status of the prototype of the LTS SQUID current monitor is discussed, and finally, the present status of the prototype of the HTS SQUID current monitor at RIKEN and the results of the first beam measurement are given. (author)

  12. Cryogenic Current Comparator as Low Intensity Beam Current Monitor in the CERN Antiproton Decelerators

    CERN Document Server

    Fernandes, M; Soby, L; Welsch, CP

    2013-01-01

    In the low-energy Antiproton Decelerator (AD) and the future Extra Low ENergy Antiproton (ELENA) rings at CERN, an absolute measurement of the beam intensity is essential to monitor any losses during the deceleration and cooling phases. However, existing DC current transformers can hardly reach the μA level, while at the AD and ELENA currents can be as low as 100 nA. A Cryogenic Current Comparator (CCC) based on a superconducting quantum interference device (SQUID) is currently being designed and shall be installed in the AD and ELENA machines. It should meet the following specifications: A current resolution smaller than 10 nA, a dynamic range covering currents between 100 nA and 1 mA, as well as a bandwidth from DC to 1 kHz. Different design options are being considered, including the use of low or high temperature superconductor materials, different CCC shapes and dimensions, different SQUID characteristics, as well as electromagnetic shielding requirements. In this contribution we present first results f...

  13. The production of high poloidal tokamak equilibria in Versator II by means of RF current drive

    International Nuclear Information System (INIS)

    Experiments on the Versator II device have been carried out in a regime of low plasma current with the aim of reaching high poloidal beta, βp. Lower-Hybrid RF current drive is used to produce an energetic electron population which carries the plasma current and pressure. In this mode of operation, plasmas with εβp approaching unity appear attainable. Data from equilibrium magnetic analysis, hard x-ray, and density profiles display an outward magnetic axis shift in agreement with equilibrium theory, and further indicate that q(O) is in the range of 4-6. PEST code modeling of these experiments suggests that some of these plasmas may be near or beyond the transition to the second stability region for ballooning modes. (author)

  14. Closure of the single fluid magnetohydrodynamic equations in presence of electron cyclotron current drive

    CERN Document Server

    Westerhof, Egbert

    2014-01-01

    In the presence of electron cyclotron current drive (ECCD), the Ohm's law of single fluid magnetohydrodynamics (MHD) is modified as ${\\bf E} + {\\bf v} \\times {\\bf B} = \\eta( {\\bf J} - {\\bf J}_{\\rm EC} )$. This paper presents a new closure relation for the EC driven current density appearing in this modified Ohm's law. The new relation faithfully represents the nonlocal character of the EC driven current and its main origin in the Fisch-Boozer effect. The closure relation is validated on both an analytical solution of an approximated Fokker-Planck equation as well as on full bounce-averaged, quasi-linear Fokker-Planck code simulations of ECCD inside rotating magnetic islands. The new model contains the model put forward by Giruzzi et al., Nucl. Fusion 39 (1999) 107, in one of its limits.

  15. Closure of the single fluid magnetohydrodynamic equations in presence of electron cyclotron current drive

    Directory of Open Access Journals (Sweden)

    Westerhof E.

    2015-01-01

    Full Text Available In the presence of electron cyclotron current drive (ECCD, the Ohm’s law of single fluid magnetohydrodynamics (MHD is modified as E + v × B = η(J – JECCD. This paper presents a new closure relation for the EC driven current density appearing in this modified Ohm’s law. The new relation faithfully represents the nonlocal character of the EC driven current and its main origin in the Fisch-Boozer effect. The closure relation is validated on both an analytical solution of an approximated Fokker-Planck equation as well as on full bounce-averaged, quasi-linear Fokker-Planck code simulations of ECCD inside rotating magnetic islands.

  16. Closure of the single fluid magnetohydrodynamic equations in presence of electron cyclotron current drive

    International Nuclear Information System (INIS)

    In the presence of electron cyclotron current drive (ECCD), the Ohm's law of single fluid magnetohydrodynamics is modified as E + v × B = η(J – JEC). This paper presents a new closure relation for the EC driven current density appearing in this modified Ohm's law. The new relation faithfully represents the nonlocal character of the EC driven current and its main origin in the Fisch-Boozer effect. The closure relation is validated on both an analytical solution of an approximated Fokker-Planck equation as well as on full bounce-averaged, quasi-linear Fokker-Planck code simulations of ECCD inside rotating magnetic islands. The new model contains the model put forward by Giruzzi et al. [Nucl. Fusion 39, 107 (1999)] in one of its limits

  17. Evolution of Wave Energy Deposition Profile in HT-7 Lower Hybrid Current Drive Experiment

    Institute of Scientific and Technical Information of China (English)

    方瑜德; 石跃江; 匡光力; 刘岳修; 沈慰慈; 丁伯江

    2001-01-01

    Lower hybrid waves (LHWs) with a selected n‖ spectrum have been used to control the energy deposition profiles, and then the wave driven current profiles effectively in tokamak discharges. In our lower hybrid current drive experiment in the HT-7 tokamak, it was found that the set-up of the wave energy deposition profile is a graduation process. In the beginning phase of the wave injection duration, the waves (with different n‖ spectra)deposit almost all their energy in the central region of the plasma column, even if their n‖ are very different. Up to around one hundred milliseconds, the wave energy deposition profiles can only take their corresponding shapes according to the n‖ spectra of LHWs. It also shown that this evolution process is affected obviously by the LHW driven current profile, which has been formed early.

  18. Broadband sidebands generated by parametric instability in lower hybrid current drive experiments on EAST

    Science.gov (United States)

    Amicucci, L.; Ding, B. J.; Castaldo, C.; Cesario, R.; Giovannozzi, E.; Li, M. H.; Tuccillo, A. A.

    2015-12-01

    Modern research on nuclear fusion energy, based on the tokamak concept, has strong need of tools for actively driving non-inductive current especially at the periphery of plasma column, where tools available so far have poor efficiency. This is essential for solving one of the most critical problems for thermonuclear reactor, consisting in how to achieve the figure of fusion gain in the context of sufficient stability. The lower hybrid current drive (LHCD) effect has the potential capability of driving current at large radii of reactor plasma with high efficiency [1]. Experiments recently carried out on EAST showed that a strong activity of LH sideband waves (from the RF probe spectra), accompanied by weak core penetration of the coupled LH power, is present when operating at relatively high plasma densities. Previous theoretical results, confirmed by experiments on FTU, showed that the LH sideband phenomenon is produced by parametric instability (PI), which are mitigated by higher plasma edge temperatures. This condition is thus useful for enabling the LH power propagation when operating with profiles having high plasma densities even at the edge. In the present work, we show new PI modeling of EAST plasmas data, obtained in condition of higher plasma edge temperature due to chamber lithisation. The obtained trend of the PI frequencies and growth rates is consistent with data of RF probe spectra, available in different regimes of lithisated and not lithisated vessel. Moreover, these spectra are interpreted as PI effect occurring at the periphery of plasma column, however in the low field side where the LH power is coupled.

  19. Broadband sidebands generated by parametric instability in lower hybrid current drive experiments on EAST

    Energy Technology Data Exchange (ETDEWEB)

    Amicucci, L., E-mail: luca.amicucci@enea.it; Castaldo, C.; Cesario, R.; Giovannozzi, E.; Tuccillo, A. A. [EUROfusion-ENEA, Centro Ricerche Frascati, Unità Fusione, Frascati (Italy); Ding, B. J.; Li, M. H. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2015-12-10

    Modern research on nuclear fusion energy, based on the tokamak concept, has strong need of tools for actively driving non-inductive current especially at the periphery of plasma column, where tools available so far have poor efficiency. This is essential for solving one of the most critical problems for thermonuclear reactor, consisting in how to achieve the figure of fusion gain in the context of sufficient stability. The lower hybrid current drive (LHCD) effect has the potential capability of driving current at large radii of reactor plasma with high efficiency [1]. Experiments recently carried out on EAST showed that a strong activity of LH sideband waves (from the RF probe spectra), accompanied by weak core penetration of the coupled LH power, is present when operating at relatively high plasma densities. Previous theoretical results, confirmed by experiments on FTU, showed that the LH sideband phenomenon is produced by parametric instability (PI), which are mitigated by higher plasma edge temperatures. This condition is thus useful for enabling the LH power propagation when operating with profiles having high plasma densities even at the edge. In the present work, we show new PI modeling of EAST plasmas data, obtained in condition of higher plasma edge temperature due to chamber lithisation. The obtained trend of the PI frequencies and growth rates is consistent with data of RF probe spectra, available in different regimes of lithisated and not lithisated vessel. Moreover, these spectra are interpreted as PI effect occurring at the periphery of plasma column, however in the low field side where the LH power is coupled.

  20. Experimental Verification of Current Shear Design Equations for HSRC Beams

    Directory of Open Access Journals (Sweden)

    Attaullah Shah

    2012-07-01

    Full Text Available Experimental research on the shear capacity of HSRC (High Strength Reinforced Concrete beams is relatively very limited as compared to the NSRC (Normal Strength Reinforced Concrete beams. Most of the Building Codes determine the shear strength of HSRC with the help of empirical equations based on experimental work of NSRC beams and hence these equations are generally regarded as un-conservative for HSRC beams particularly at low level of longitudinal reinforcement. In this paper, 42 beams have been tested in two sets, such that in 21 beams no transverse reinforcement has been used, whereas in the remaining 21 beams, minimum transverse reinforcement has been used as per ACI-318 (American Concrete Institute provisions. Two values of compressive strength 52 and 61 MPa, three values of longitudinal steel ratio and seven values of shear span to depth ratio have been have been used. The beams were tested under concentrated load at the mid span. The results are compared with the equations proposed by different international building codes like ACI, AASHTO LRFD, EC (Euro Code, Canadian Code and Japanese Code for shear strength of HSRC beams.From comparison, it has been observed that some codes are less conservative for shear design of HSRC beams and further research is required to rationalize these equations.

  1. Comparative modelling of lower hybrid current drive with two launcher designs in the Tore Supra tokamak

    International Nuclear Information System (INIS)

    Fully non-inductive operation with lower hybrid current drive (LHCD) in the Tore Supra tokamak is achieved using either a fully active multijunction (FAM) launcher or a more recent ITER-relevant passive active multijunction (PAM) launcher, or both launchers simultaneously. While both antennas show comparable experimental efficiencies, the analysis of stability properties in long discharges suggest different current profiles. We present comparative modelling of LHCD with the two different launchers to characterize the effect of the respective antenna spectra on the driven current profile. The interpretative modelling of LHCD is carried out using a chain of codes calculating, respectively, the global discharge evolution (tokamak simulator METIS), the spectrum at the antenna mouth (LH coupling code ALOHA), the LH wave propagation (ray-tracing code C3PO), and the distribution function (3D Fokker–Planck code LUKE). Essential aspects of the fast electron dynamics in time, space and energy are obtained from hard x-ray measurements of fast electron bremsstrahlung emission using a dedicated tomographic system. LHCD simulations are validated by systematic comparisons between these experimental measurements and the reconstructed signal calculated by the code R5X2 from the LUKE electron distribution. An excellent agreement is obtained in the presence of strong Landau damping (found under low density and high-power conditions in Tore Supra) for which the ray-tracing model is valid for modelling the LH wave propagation. Two aspects of the antenna spectra are found to have a significant effect on LHCD. First, the driven current is found to be proportional to the directivity, which depends upon the respective weight of the main positive and main negative lobes and is particularly sensitive to the density in front of the antenna. Second, the position of the main negative lobe in the spectrum is different for the two launchers. As this lobe drives a counter-current, the resulting

  2. The targeted heating and current drive applications for the ITER electron cyclotron system

    International Nuclear Information System (INIS)

    A 24 MW Electron Cyclotron (EC) system operating at 170 GHz and 3600 s pulse length is to be installed on ITER. The EC plant shall deliver 20 MW of this power to the plasma for Heating and Current Drive (H and CD) applications. The EC system is designed for plasma initiation, central heating, current drive, current profile tailoring, and Magneto-hydrodynamic control (in particular, sawteeth and Neo-classical Tearing Mode) in the flat-top phase of the plasma. A preliminary design review was performed in 2012, which identified a need for extended application of the EC system to the plasma ramp-up, flattop, and ramp down phases of ITER plasma pulse. The various functionalities are prioritized based on those applications, which can be uniquely addressed with the EC system in contrast to other H and CD systems. An initial attempt has been developed at prioritizing the allocated H and CD applications for the three scenarios envisioned: ELMy H-mode (15 MA), Hybrid (∼12 MA), and Advanced (∼9 MA) scenarios. This leads to the finalization of the design requirements for the EC sub-systems

  3. RF heating and current drive experiments on the Alcator C and Versator II tokamaks

    International Nuclear Information System (INIS)

    Lower hybrid heating and current drive experiments on the Alcator C tokamak (R = 0.64 m, a = 0.165 m, molybdenum limiters) were performed at a frequency of 4.6 GHz with net injected rf powers up to P/sub rf/ ≤ 1.5 MW. Recent experiments have focused on energy confinement studies in lower hybrid current-driven (LHCD) and LHRF heated Ohmic discharges, and sawtooth stabilization in combined LHCD-OH driven discharges at densities n-bar/sub e/ ≤ 1.4 x 1020 m-3. Ion Bernstein wave heating experiments were also carried out in Alcator C at a frequency of f = 183 MHz at power levels P/sub rf/ ≤ 200 kW. Significant heating (ΔT/sub i/ ≤ 400 eV) was observed at ω/ω/sub CH/ ≅ 1.5, 2.5 and ω/ω/sub CD/ ≅ 2.5 at densities n-bar/sub e/ ≅ 1 x 1020 m-3. In the Versator II tokamak, particle confinement improvement (by factors of ≅2) was observed in the presence of 2.45 GHz lower hybrid current drive

  4. RF heating and current drive experiments on the Alcator C and Versator II tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Porkolab, M.; Bonoli, P.; Chen, K.I.; Fiore, C.; Granetz, R.; Griffin, D.; Gwinn, D.; Knowlton, S.; Lipschultz, B.; Luckhardt, S.C.

    1986-11-01

    Lower hybrid heating and current drive experiments on the Alcator C tokamak (R = 0.64 m, a = 0.165 m, molybdenum limiters) were performed at a frequency of 4.6 GHz with net injected rf powers up to P/sub rf/ less than or equal to 1.5 MW. Recent experiments have focused on energy confinement studies in lower hybrid current-driven (LHCD) and LHRF heated Ohmic discharges, and sawtooth stabilization in combined LHCD-OH driven discharges at densities n-bar/sub e/ less than or equal to 1.4 x 10/sup 20/ m/sup -3/. Ion Bernstein wave heating experiments were also carried out in Alcator C at a frequency of f = 183 MHz at power levels P/sub rf/ less than or equal to 200 kW. Significant heating (..delta..T/sub i/ less than or equal to 400 eV) was observed at ..omega../..omega../sub CH/ approx. = 1.5, 2.5 and ..omega../..omega../sub CD/ approx. = 2.5 at densities n-bar/sub e/ approx. = 1 x 10/sup 20/ m/sup -3/. In the Versator II tokamak, particle confinement improvement (by factors of approx. =2) was observed in the presence of 2.45 GHz lower hybrid current drive.

  5. Core and edge electron dynamics during lower hybrid current drive experiments

    International Nuclear Information System (INIS)

    Characterisation of the core and edge fast electron dynamics during lower hybrid (LH) current drive experiments is a critical issue in view to achieve improved plasma performances by tailoring the current density profile in a steady state manner. At low power input (PLH ≤ 2MW), the localisation of the LH wave absorption exhibits a correlation with the radial position of the q=1 surface in the plasma, as deduced from magnetic measurements and equilibrium code predictions. Such an effect is observed either in stationary or transient conditions during LH assisted ramp-up experiments. The lack of LH power deposition in the core of the plasma is also confirmed by analysis of giant sawteeth in combined ICRH-LH scenarios. The implications of these results for theories of the LH wave dynamics in the plasma and current density profile control are discussed. LH power dissipation at the plasma edge, which may lead to anomalous heat loads on components magnetically connected to the radiating waveguide array is investigated theoretically and experimental data are compared to calculations. The key role played by the fraction of high-nparallel values of the LH wave power spectrum as well as the edge plasma density in the acceleration of thermal electrons is identified, and the possibility of an additional driving force is also discussed. The effect of the shape of the LH waveguide septa is analysed both theoretically and experimentally. (author)

  6. Core and edge electron dynamics during lower hybrid current drive experiments

    International Nuclear Information System (INIS)

    Characterisation of the core and edge fast electron dynamics during lower hybrid (LH) current drive experiments is a critical issue in view to achieve improved plasma performances by tailoring the current density profile in a steady state manner. At low power input (PLH≤2MW), the localisation of the LH wave absorption exhibits a correlation with the radial position of the q=1 surface in the plasma, as deduced from magnetic measurements and equilibrium code predictions. Such an effect is observed either in stationary or transient conditions during LH assisted ramp-up experiments. The lack of LH power deposition in the core of the plasma is also confirmed by analysis of giant sawteeth in combined ICRH-LH scenarios. The implications of these results for theories of the LH wave dynamics in the plasma and current density profile control are discussed. LH power dissipation at the plasma edge, which may lead to anomalous heat loads on components magnetically connected to the radiating waveguide array is investigated theoretically and experimental data are compared to calculations. The key role played by the fraction of high-nparallel values of the LH wave power spectrum as well as the edge plasma density in the acceleration of thermal electrons is identified, and the possibility of an additional driving force is also discussed. The effect of the shape of the LH waveguide septa is analysed both theoretically and experimentally. (author)

  7. Fast electron dynamics during lower hybrid current drive experiments in the HT-7 tokamak

    International Nuclear Information System (INIS)

    Characterization of fast electron dynamics during lower hybrid current drive (LHCD) experiments is a critical issue for achieving enhanced plasma performance. A new hard X-ray diagnostics system that has been installed recently on HT-7 with 10 lines of sight, and 128 energy channels between 20 and 200 keV for each detector, has allowed the investigation of the lower hybrid wave dynamics. The behavior of fast electrons was studied in several kinds of LHCD experiments, including long pulse discharges, high parameter discharges and counter-LHCD experiments. (author)

  8. Angular distribution of the bremsstrahlung emission during lower-hybrid current drive on PLT

    International Nuclear Information System (INIS)

    The bremsstrahlung emission from the PLT tokamak during lower-hybrid current drive has been measured as a function of angle between the magnetic field and the emission direction. The emission is peaked strongly in the forward direction, indicating a strong anisotropy of the electron-velocity distribution. The data demonstrate the existence of a nearly flat tail of the velocity distribution, which extends out to approximately 500 keV and which is interpreted as the plateau created by Landau damping of the lower-hybrid waves

  9. On variational formulation of current drive problem in uniformly magnetized relativistic plasma

    Science.gov (United States)

    Hu, Y. M.; Hu, Y. J.

    2016-01-01

    A fully relativistic extension of the variational principle with the modified test function for the Spitzer function with momentum conservation in the electron-electron collision is investigated in uniformly magnetized plasma. The term of the momentum conserving constraint in Hirshman’s variational calculation is studied. The model developed is extended for arbitrary temperatures and covers exactly the asymptotic for u\\gg 1 when {{Z}\\text{eff}}\\gg 1 , and the results obtained are suited to facilitate the development of a rigorous variational formulation of current drive efficiency in tokamak plasma.

  10. Destabilization of fast particle stabilized sawteeth in ASDEX Upgrade with electron cyclotron current drive

    DEFF Research Database (Denmark)

    Igochine, V.; Chapman, I.T.; Bobkov, V.; Günter, S.; Maraschek, M.; Moseev, Dmitry; Pereversev, G.; Reich, M.; Stober, J.

    2011-01-01

    It is often observed that large sawteeth trigger the neoclassical tearing mode well below the usual threshold for this instability. At the same time, fast particles in the plasma core stabilize sawteeth and provide these large crashes. The paper presents results of first experiments in ASDEX...... Upgrade for destabilization of fast particle stabilized sawteeth with electron cyclotron current drive (ECCD). It is shown that moderate ECCD from a single gyrotron is able to destabilize the fast particle stabilized sawteeth. A reduction in sawtooth period by about 40% was achieved in first experiments...

  11. A survey of electron Bernstein wave heating and current drive potential for spherical tokamaks

    Czech Academy of Sciences Publication Activity Database

    Urban, Jakub; Decker, J.; Peysson, Y.; Preinhaelter, Josef; Shevchenko, V.; Taylor, G.; Vahala, L.; Vahala, G.

    2011-01-01

    Roč. 51, č. 8 (2011), 083050-083050. ISSN 0029-5515 R&D Projects: GA ČR GA202/08/0419; GA MŠk 7G10072 Institutional research plan: CEZ:AV0Z20430508 Keywords : spherical tokamak * electron Bernstein wave (EBW) * heating * current drive * electron cyclotron wave Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.090, year: 2011 http://iopscience.iop.org/0029-5515/51/8/083050/pdf/0029-5515_51_8_083050.pdf

  12. Development of a prototype T-shaped fast switching device for electron cyclotron current drive systems

    Science.gov (United States)

    Sekiguchi, Kenji; Nagashima, Koji; Honzu, Toshihiko; Saigusa, Mikio; Oda, Yasuhisa; Takahashi, Koji; Sakamoto, Keishi

    2016-09-01

    A T-shaped high-power switching device composed of circular corrugated waveguides with three ports and double dielectric disks made of sapphire was proposed as a fast switching device based on a new principle in electron cyclotron current drive systems. This switching device has the advantages of operating at a fixed frequency and being compact. The design of the prototype switch was obtained by numerical simulations using a finite-difference time-domain (FDTD) method. The size of these components was optimized for the frequency band of 170 GHz. Low-power tests were carried out in a cross-shaped model.

  13. Effects of electron cyclotron current drive on the evolution of double tearing mode

    International Nuclear Information System (INIS)

    The effects of electron cyclotron current drive (ECCD) on the double tearing mode (DTM) in slab geometry are investigated by using two-dimensional compressible magnetohydrodynamics equations. It is found that, mainly, the double tearing mode is suppressed by the emergence of the secondary island, due to the deposition of driven current on the X-point of magnetic island at one rational surface, which forms a new non-complete symmetric magnetic topology structure (defined as a non-complete symmetric structure, NSS). The effects of driven current with different parameters (magnitude, initial time of deposition, duration time, and location of deposition) on the evolution of DTM are analyzed elaborately. The optimal magnitude or optimal deposition duration of driven current is the one which makes the duration of NSS the longest, which depends on the mutual effect between ECCD and the background plasma. Moreover, driven current introduced at the early Sweet-Parker phase has the best suppression effect; and the optimal moment also exists, depending on the duration of the NSS. Finally, the effects varied by the driven current disposition location are studied. It is verified that the favorable location of driven current is the X-point which is completely different from the result of single tearing mode

  14. Effects of electron cyclotron current drive on the evolution of double tearing mode

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Guanglan, E-mail: sunguanglan@nciae.edu.cn; Dong, Chunying [Basic Science Section, North China Institute of Aerospace Engineering, Langfang 065000 (China); Duan, Longfang [School of Computer and Remote Sensing Information Technology, North China Institute of Aerospace Engineering, Langfang 065000 (China)

    2015-09-15

    The effects of electron cyclotron current drive (ECCD) on the double tearing mode (DTM) in slab geometry are investigated by using two-dimensional compressible magnetohydrodynamics equations. It is found that, mainly, the double tearing mode is suppressed by the emergence of the secondary island, due to the deposition of driven current on the X-point of magnetic island at one rational surface, which forms a new non-complete symmetric magnetic topology structure (defined as a non-complete symmetric structure, NSS). The effects of driven current with different parameters (magnitude, initial time of deposition, duration time, and location of deposition) on the evolution of DTM are analyzed elaborately. The optimal magnitude or optimal deposition duration of driven current is the one which makes the duration of NSS the longest, which depends on the mutual effect between ECCD and the background plasma. Moreover, driven current introduced at the early Sweet-Parker phase has the best suppression effect; and the optimal moment also exists, depending on the duration of the NSS. Finally, the effects varied by the driven current disposition location are studied. It is verified that the favorable location of driven current is the X-point which is completely different from the result of single tearing mode.

  15. Development of capacitive beam position, beam current and Schottky-signal monitors for the Cryogenic Storage Ring (CSR)

    International Nuclear Information System (INIS)

    In this thesis novel techniques based on capacitive pickups for the determination of the beam current, the beam position and the Schottky-signal in storage rings have been developed. Beam current measurements at the heavy ion storage ring TSR with a capacitive pickup have been found in very good agreement with the theory. Using this device the accurate measurement of beam currents at the TSR far below 1 μA is now possible. This method will also be used at the Cryogenic Storage Ring (CSR) at which beam currents in the range of 1 nA-1 μA are expected. For the first time, position measurements with a resonant amplifier system for capacitive pickups have been examined at the TSR for later use of this technique in the CSR. With this method an increased signal-to-noise ratio can be achieved using a parallel inductance. A comparison with measurements using the rest gas beam profile monitor has shown very good agreement even at very low intensities. Experiments with the cryo-capable electronics for the CSR beam position monitors have shown an achievable quality factor of Q=500, resulting in the prospect of precise position measurements at the CSR even at very low beam currents. The CSR Schottky-Pickup will also be equipped with a resonant amplifier system with a comparable quality factor. An estimation of the signal-to-noise ratio suggests a detection limit of a few protons. (orig.)

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

    Science.gov (United States)

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

    2014-05-01

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

  17. Improvements of a beam current monitor by using a high Tc current sensor and SQUID at the RIBF

    International Nuclear Information System (INIS)

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

  18. Filtered neutron beams at the FMRB - review and current status

    International Nuclear Information System (INIS)

    A review is presented of our experience with filtered neutron beams installed in beam tubes of the Research and Measurement Reactor Braunschweig since 1976: Desing of the filters and measurement of the beam parameters are reported and an outline of the research work done with the beams is given. The present status of the irradiation facility, which consists of 5 beams (144 keV, 24.5 keV, 2 keV, 0.2 keV and thermal neutrons), is described in some detail to allow understanding of the physical as well as the technical prerequisites for performing calibrations of neutron measuring instruments. An appendix contains the actual beam parameters. (orig.)

  19. Direct Drive and Eddy Current Septa Magnet Designs for CERN’s PSB Extraction at 2 GeV

    CERN Multimedia

    Szoke, Zsolt; Balhan, Bruno; Baud, Cedric; Borburgh, Jan; Hourican, Michael; Masson, Thierry; Prost, Antoine

    2015-01-01

    In the framework of the LIU project, new septa magnets have been designed between CERN’s PS Booster (PSB) extraction and PS injection. The upgraded devices are to deal with the increased beam energy from 1.4 GeV to 2 GeV at extraction of the PSB. The direct drive recombination septa in the PSB transfer line to the PS, the eddy current PS injection septum together with a bumper at injection have been investigated using finite element software. For the recombination magnets an increase in magnet length is sufficient to obtain the required deflection; however, for the PS injection elements a more novel solution is necessary to also achieve increased robustness to extend the expected lifetime of the pulsed device. The injection septum will share the same vacuum vessel with an injection bumper and both magnets will be located adjacent to each other. The new PS injection magnet will be the first septum operated at CERN based on eddy current technology. The magnetic modelling of the devices, the comparison of the ...

  20. Non-inductive current drive with suprathermal ions and electrons in reactor-grade tokamak plasmas: A comparison

    International Nuclear Information System (INIS)

    It is now widely accepted that a prospective fusion reactor will be a tokamak configuration and operate in steady-state. Two main requirements must be met in order to have this toroidal magnetic confinement scheme running in a truely stationary mode: the ion species composition in the plasma and its radial distribution must be controlled; the toroidal current through the plasma must be sustained by non-inductive means. The first condition implies, for example, the supply of fuel ions to the plasma centre at adequate rates, as well as the presence of non-fuel ions/atoms at the plasma edge to radiate away part of the outward-streaming heat power. With regard to the second requirement: completely non-inductive current-drive with fast ions or electrons has already been demonstrated experimentally. Some examples will be discussed below in more detail. The fast ions were created by injecting neutral beams of high-energy atoms, the suprathermal electrons by Landau-resonance of bulk plasma electrons with lower hybrid waves travelling along the magnetic field lines, they were launched as slow waves at the plasma edge. (orig./AH)

  1. Modeling of the influence of the driving laser wavelength on the beam quality of transiently pumped X-ray lasers

    Science.gov (United States)

    Le Pape, S.; Zeitoun, Ph.

    2003-04-01

    A three dimensional ray tracing code (SHADOX) has been developed, as a post-processor of any hydrodynamic/atomic code, to model X-ray laser beam propagation along the amplifying medium and any optical component. In this paper we show a study aimed to investigate the influence of the long driving pulse wavelength on the transiently pumped X-ray laser propagation and amplification. Different pumping configurations have been modeled and their respective influence on the beam quality has been investigated. This work shows that the beam homogeneity is highly sensitive to both the emissive zone dimension and electron density gradient and that pumping by a double pulse in a two-color configuration (2 ω/ ω; Δt=200 ps) is favorable in terms of beam quality.

  2. Advanced Tokamak Regimes in Alcator C-Mod with Lower Hybrid Current Drive

    Science.gov (United States)

    Parker, R.; Bonoli, P.; Gwinn, D.; Hutchinson, I.; Porkolab, M.; Ramos, J.; Bernabei, S.; Hosea, J.; Wilson, R.

    1999-11-01

    Alcator C-Mod has been proposed as a test-bed for developing advanced tokamak scenarios owing to its strong shaping, relatively long pulse length capability at moderate field, e.g. t ~ L/R at B = 5T and T_eo ~ 7keV, and the availability of strong ICRF heating. We plan to exploit this capability by installing up to 4 MW RF power at 4.6 GHz for efficient off-axis current drive by lower hybrid waves. By launching LH waves with a grill whose n_xx spectrum can be dynamically controlled over the range 2 2. Such reversed or nearly zero shear regimes have already been proposed as the basis of an advanced tokamak burning-plasma experiment-ATBX (M. Porkolab et al, IAEA-CN-69/FTP/13, IAEA,Yokohama 1998.), and could provide the basis for a demonstration power reactor. Theoretical and experimental basis for this advanced tokamak research program on C-Mod, including design of the lower hybrid coupler, its spectrum and current drive capabilities will be presented.

  3. Review of tokamak experiments on direct electron heating and current drive with fast waves

    International Nuclear Information System (INIS)

    Results from tokamak experiments on direct electron interaction with the compressional Alfven wave (open-quote fast wave close-quote) are reviewed. Experiments aimed at electron heating as well as those in which fast wave electron current drive was investigated are discussed. A distinction is drawn between experiments employing the lower hybrid range of frequencies, where both the lower hybrid wave (open-quote slow wave close-quote) and the fast wave can propagate in much of the plasma, and those experiments using the fast wave in the range of moderate to high ion cyclotron harmonics, where only the fast wave can penetrate to the plasma core. Most of the early tokamak experiments were in the lower hybrid frequency regime, and the observed electron interaction appeared to be very similar to that obtained with the slow wave at the same frequency. In particular, electron interaction with the fast wave was observed only below a density limit nearly the same as the well known slow wave density limit. In the more recent lower frequency fast wave experiments, electron interaction (heating and current drive) is observed at the center of the discharge, where slow waves are not present

  4. Development of hybrid frequency couplers for non-inductive current drive in a tokamak

    International Nuclear Information System (INIS)

    Used at its first time as an heating method in order to reach the temperature requisite for the fusion of a thermonuclear plasma, the hybrid waves has shown that they were the more efficient method for non-inductive current drive in a tokamak. The size and the objectives of a next machine such as ITER lead of the design of new antennae (in process of realisation on Tore Supra) made of oversized waveguides. This new concept of antenna will be more simple, more robust and will be able to transmit the same if not much power than the present antennae. This thesis contribute to the development of a new code called ALOHA (for 'Advanced LOwer Hybrid Antenna') which, at the end, will be able to give the characteristics and the behaviours of this new oversized antennae in front of a tokamak plasma. This thesis is also a first step in the interpretation of some experimental data concerning the measurement of coupling, absorption and current drive of the actual hybrid wave launched by a grill with rectangular waveguides. Moreover, this thesis lay some foundations of the study of these new antennae in front of a non-parallel confinement magnetic field and/or in front of poloidal inhomogeneities of plasma. (author)

  5. Simulation study of proposed off-midplane lower hybrid current drive in KSTAR

    Science.gov (United States)

    Bae, Young-soon; Shiraiwa, S.; Bonoli, P.; Wallace, G.; Wright, J. C.; Parker, R.; Kim, J. H.; Namkung, W.; Cho, M. H.; Park, B. H.; Yoon, S. W.; Oh, Y. K.; Park, H.

    2016-07-01

    A new proposal of lower hybrid (LH) wave launching is studied for efficient current drive aiming for high performance H-mode operation in Korea Superconducting Tokamak Advanced Research (KSTAR). This new concept is the off-midplane launch which results in a rapid up-shift of the parallel component of refractive index and hence simultaneously maintains good wave accessibility and efficient single pass absorption via Landau damping. In order to locate an optimal position of the launcher in the poloidal direction, the ray-tracing and Fokker–Planck codes were used. Based on a survey of the LH wave launch parameters and operation conditions including the compatibility issues with the existing in-vessel components, the LH wave launch from the top position near the upper X-point of the plasma separatrix provides the possibility to eliminate the accessibility problem and reduce parasitic edge loss for the KSTAR high performance H-mode operation scenario using 5 GHz lower hybrid current drive.

  6. Simulations of fast-wave current drive in pulsed and steady-state DEMO designs

    Science.gov (United States)

    Bilato, R.; Brambilla, M.; Fable, E.

    2014-11-01

    Electromagnetic waves in the ion-cyclotron (IC) range of frequencies are presently investigated as possible current drive (CD) systems in fusion reactors. Among many physical and technical issues, an accurate description of radio-frequency (RF) power absorption by fusion- born alpha particles is of special importance, since RF heating of these particles is not only detrimental for the CD efficiency, but might worsen the operative conditions by increasing their prompt losses. The capability of the full-wave TORIC code has been recently augmented to account for RF absorption by fusion-born alpha particles, calculated to all-orders in finite Larmor radius and with a realistic distribution function. Here, we present simulation with TORIC addressing the sensitivity of current drive efficiency on the design of a future reactor, in particular density and temperature profiles, magnetic field intensity, and plasma dimensions. For this purpose, we have investigated possible frequency windows for CD for two proposed versions of the DEMO reactor, namely its pulsed and its more ambitious steady-state design. The important role of the antenna for a realistic estimate of the CD efficiency is pointed out.

  7. Experimental and modeling uncertainties in the validation of lower hybrid current drive

    Science.gov (United States)

    Poli, F. M.; Bonoli, P. T.; Chilenski, M.; Mumgaard, R.; Shiraiwa, S.; Wallace, G. M.; Andre, R.; Delgado-Aparicio, L.; Scott, S.; Wilson, J. R.; Harvey, R. W.; Petrov, Yu V.; Reinke, M.; Faust, I.; Granetz, R.; Hughes, J.; Rice, J.

    2016-09-01

    This work discusses sources of uncertainty in the validation of lower hybrid wave current drive simulations against experiments, by evolving self-consistently the magnetic equilibrium and the heating and current drive profiles, calculated with a combined toroidal ray tracing code and 3D Fokker–Planck solver. The simulations indicate a complex interplay of elements, where uncertainties in the input plasma parameters, in the models and in the transport solver combine and—in some cases—compensate each other. It is concluded that ray-tracing calculations should include a realistic representation of the density and temperature in the region between the confined plasma and the wall, which is especially important in regimes where the LH waves are weakly damped and undergo multiple reflections from the plasma boundary. Uncertainties introduced in the processing of diagnostic data as well as uncertainties introduced by model approximations are assessed. It is shown that, by comparing the evolution of the plasma parameters in self-consistent simulations with available data, inconsistencies can be identified and limitations in the models or in the experimental data assessed.

  8. Transient analysis of electromagnets with emphasis on solid components, eddy currents, and driving circuitry

    Science.gov (United States)

    Batdorff, Mark A.

    Valves are commonly used in fluid power systems to control pressure and flow. The emerging field of digital hydraulics demands high-speed, low cost, on/off valves with improved performance. Electromagnets, or solenoids, are commonly used to actuate valves due to their low cost, high reliability, and moderate performance. This work develops a dynamic model for a solid steel electromagnet that can be used for design and optimization, and unveils design tradeoffs with geometry and driving circuitry that are often overlooked. This work develops an accurate, computationally efficient, nonlinear, coupled, dynamic, axisymmetric, high fidelity magnetic equivalent circuit (HFMEC) electromagnet model capable of predicting force, inductance, dynamic response, and energy consumption. The model is intended for applications where both accuracy and solution time are critical. Axisymmetric magnetic fringing and leakage permeances were derived in order to capture nonlinear magnetic field phenomena that affect force and inductance. The tradeoffs between solid-center and hollow-center electromagnets were investigated. It was shown with both simulation and measurement that a hollow-center electromagnet has a 37.7% shorter useful stroke due to increased magnetic fringing and leakage (from 4.0mm to 2.5mm). However, it was also shown that the hollow-center electromagnet has a 70% improved turn-off response (from 617ms to 362ms). A single objective optimization study was performed demonstrating that hollow-center electromagnets are advantageous and can up to 204% increased dynamic response for systems where dynamics are dominated by eddy current lag. Electromagnets experience dynamic lag when turning on and off due to inductance and eddy currents. Coil driving methods, such as peak-and-hold, are often used to minimize turn-on lag by using high initial voltages and currents. However, circuits often do not address turn-off lag, which can be significant. This work investigates the effects of

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

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S. H. (Accelerator Systems Division (APS))

    2012-03-27

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

  10. Ion cyclotron and lower hybrid arrays applicable to current drive in fusion reactors

    Science.gov (United States)

    Bosia, G.; Helou, W.; Goniche, M.; Hillaret, J.; Ragona, R.

    2014-02-01

    This paper presents concepts for Ion Cyclotron and Lower Hybrid Current Drive arrays applicable to fusion reactors and based on periodically loaded line power division. It is shown that, in large arrays, such as the ones proposed for fusion reactor applications, these schemes can offer, in principle, a number of practical advantages, compared with currently adopted ones, such as in-blanket operation at significantly reduced power density, lay out suitable for water cooling, single ended or balanced power feed, simple and load independent impedance matching In addition, a remote and accurate real time measurement of the complex impedance of all array elements as well as detection, location, and measurement of the complex admittance of a single arc occurring anywhere in the structure is possible.

  11. Alfven wave spectrum control in the heating and current drive experiments

    International Nuclear Information System (INIS)

    In this report we present the diagnostic system that has been developed for wave field spectrum analysis and control during Alfven wave heating and current drive experiments in the TCABR tokamak The system permits to register simultaneously the phase and the amplitude of the toroidal Β-tilde φ and poloidal Β-tildeθ magnetic field components of the waves with M ±1, N = ±, N = ±(2+6) in the frequency range ∫ = 2-8 MHz and RF pulse duration τ = 20-50 ms and to generate a feedback signal for plasma parameters control. The wave mode and frequency selectivity are ensured by the adjustment of the magnetic probe position and by utilization of specially designed 'lock-in' amplifiers that use 'sin' and 'cos' reference signals produced on the basis of the Alfven antenna feeding current. (author)

  12. The 15 MW microwave generator and launcher of the lower hybrid current drive experiment on JET

    International Nuclear Information System (INIS)

    The lower hybrid current drive experiment on JET, aimed at generating current in the plasma by launching a wave at 3.7 GHz into the torus, required the building of a large high power microwave generator and antenna. The generator can provide 15 MW for 10 seconds or 12 MW for 20 seconds. This power will be fed to a phased-array antenna consisting of 48 stainless steel modules assembled in an array of 384 waveguides. The antenna position will be controlled in real time in order to optimize the coupling to the plasma. The phasing between different modules can be set so as to vary the N// between 1.8 and 2.4. 4 refs., 5 figs., 1 tab

  13. Microturbulence studies of pulsed poloidal current drive discharges in the reversed field pinch

    Energy Technology Data Exchange (ETDEWEB)

    Carmody, D., E-mail: dcarmody@wisc.edu; Pueschel, M. J.; Anderson, J. K.; Terry, P. W. [University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

    2015-01-15

    Experimental discharges with pulsed poloidal current drive (PPCD) in the Madison Symmetric Torus reversed field pinch are investigated using a semi-analytic equilibrium model in the gyrokinetic turbulence code GENE. PPCD cases, with plasma currents of 500 kA and 200 kA, exhibit a density-gradient-driven trapped electron mode (TEM) and an ion temperature gradient mode, respectively. Relative to expectations of tokamak core plasmas, the critical gradients for the onset of these instabilities are found to be greater by roughly a factor of the aspect ratio. A significant upshift in the nonlinear TEM transport threshold, previously found for tokamaks, is confirmed in nonlinear reversed field pinch simulations and is roughly three times the threshold for linear instability. The simulated heat fluxes can be brought in agreement with measured diffusivities by introducing a small, resonant magnetic perturbation, thus modeling the residual fluctuations from tearing modes. These fluctuations significantly enhance transport.

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

    International Nuclear Information System (INIS)

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

  15. Capabilities of the ITER Electron Cyclotron Equatorial Launcher for Heating and Current Drive

    Directory of Open Access Journals (Sweden)

    Ramponi G.

    2012-09-01

    Full Text Available The ITER Electron Cyclotron Equatorial Launcher is designed to be one of the heating systems to assist and sustain the development of various ITER plasma scenarios starting with the very first plasma operation. Here the capabilities for Heating and Current Drive of this system are reviewed. In particular, the optimum launching conditions are investigated for two scenarios at burn, comparing toroidal and poloidal steering options. Then, the EC capabilities are investigated for different plasma parameters corresponding to various phases of the ITER plasma discharge, from current ramp-up up to burn, and for a wide range of magnetic field, focusing in particular on the EC potential for heating and for L to H-mode assist. It is found that the EC system can contribute to a wide range of heating scenarios during the ramp-up of the magnetic field, significantly increasing the applicable range as a function of magnetic field.

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

    Energy Technology Data Exchange (ETDEWEB)

    Swanekamp, S. B.; Richardson, A. S.; Angus, J. R.; Cooperstein, G.; Hinshelwood, D. D.; Ottinger, P. F.; Rittersdorf, I. M.; Schumer, J. W.; Weber, B. V.; Zier, J. C. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States)

    2015-02-15

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

  17. Overlapping laser profiles used to mitigate the negative effects of beam uncertainties in direct-drive LMJ configurations

    International Nuclear Information System (INIS)

    A direct-drive shock ignition scheme in the context of the Laser Mega Joule facility has been considered. The irradiation uniformity provided by two laser beam configurations using a total of 10 or 20 quads to drive the first compression phase has been analyzed. Firstly, a numerical method is used to optimize the laser intensity profiles in the context of the illumination approximation model; then these profiles are used to calculate the irradiation non-uniformity of a spherical target of radius r0 = 1000 μm assuming the beam uncertainties: power imbalance 5%, pointing error 50 μm and target positioning 20 μm. These uncertainties deteriorate the quality of the irradiation increasing considerably the irradiation non-uniformity; moreover, it is found that the pointing error provides the major contribution to the degradation of the irradiation. A strategy to mitigate the negative effect induced by the beam uncertainties is proposed. It consists in using a composite profile in each beam: a first large and flat intensity profile provides a background that reduces pointing error and target positioning effects, whilst a second overlapping profile optimizes the illumination irradiation. It is found that the introduction of the flat background with an intensity of 55% with respect to the maximum intensity reduces by about 40% the non-uniformity of the irradiation due to beam uncertainties. (authors)

  18. Spontaneous short-wave radiation of high-current electron beam

    International Nuclear Information System (INIS)

    Angular and spectral characteristics of spontaneous radiation of high-current electron beam in a proper magnetic field are theoretically investigated. The model of a cylindrically- symmetric non rotating stationary beam the space charge of which is completely compensated by a motionless ion background has been used. It is shown that the radiation considerably depends on the beam current, its directivity with current increase drops, total intensity grows, but the spectrum widens

  19. Demonstration of Multipulsed Current Drive Scenario using Coaxial Helicity Injection in the HIST Spherical Torus Plasmas

    International Nuclear Information System (INIS)

    Full text: The Helicity Injected Spherical Torus (HIST) device has been developed towards high-current start up and sustainment by Mutipulsed Coaxial Helicity Injection (M-CHI) method. Multiple pulses operation of the coaxial plasma gun can build the magnetic field of spherical torus (ST) and spheromak plasmas in a stepwise manner. Successive double gun pulses have been demonstrated to amplify the magnetic field and the plasma current against resistive decay. The resistive 3D-MHD numerical simulation has reproduced the current amplification by the M-CHI method and confirmed that stochastic magnetic field is reduced so that closed flux surfaces are created during the current drive. These experimental and computational results from STs have provided, for the first time, availability of a quasi-steady-state 'refluxing' mode in which the magnetic field is allowed to decay partially before being rebuilt. Our goal is to achieve simultaneously the good energy confinement and the current sustainment by the M-CHI method. (author)

  20. Development of long pulse radiofrequency heating and current drive systems and scenarios for WEST

    International Nuclear Information System (INIS)

    The longstanding expertise of the Tore Supra Team in long pulse radiofrequency (RF) heating and current drive systems will now be exploited in WEST (tungsten-W Environment in Steady-state Tokamak). WEST will allow an integrated long pulse tokamak programme for testing W-divertor components at ITER-relevant heat flux (10-20 MW/m2), while treating crucial aspects for ITER-operation, such as avoidance of W-accumulation in long discharges, monitoring and control of heat fluxes on the metallic plasma facing components (PFCs) and coupling of RF waves in H-mode plasmas. Scenario modelling using the METIS-code shows that ITER-relevant heat fluxes are compatible with the sustainment of long pulse H-mode discharges, at high power (up to 15 MW/30s at IP = 0.8 MA) or high fluence (up to 10 MW, up to 1000s at IP = 0.6 MA), all based on RF heating and current drive using Ion Cyclotron Resonance Heating (ICRH) and Lower Hybrid Current Drive (LHCD). To allow coupling to H-mode plasmas, three ELM-resilient ICRH antennas have been designed for WEST. They will be fabricated and provided as in-kind contribution by ASIPP (Hefei), within the framework of the Associated Laboratory IRFM-ASIPP. Furthermore, the ICRH generator has been upgraded to allow high power operation (9 MW/30s) at high reflected power (VSWR = 2). The WEST ICRH system is thus the first ever ICRH system combining continuous wave (CW) operation at high power and load tolerance capability for coupling on H-modes. The nominal operating frequencies are 53±2 MHz and 55.5± 2 MHz, in order to allow flexibility in the location of the resonance layer around the magnetic axis. The LHCD system, with capability to inject 7 MW/1000s, is an indispensable tool for long pulse scenarios. The LH power deposition and current profiles have been modelled with the recent 'Tail LH' model in C3PO/LUKE, which has proven to reproduce well the experimental LHCD results on Tore Supra, as well as on EAST. The simulations show that the

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

    Science.gov (United States)

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

    2015-05-01

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

  2. Isolating and quantifying cross-beam energy transfer in direct-drive implosions on OMEGA and the National Ignition Facility

    Science.gov (United States)

    Davis, A. K.; Cao, D.; Michel, D. T.; Hohenberger, M.; Edgell, D. H.; Epstein, R.; Goncharov, V. N.; Hu, S. X.; Igumenshchev, I. V.; Marozas, J. A.; Maximov, A. V.; Myatt, J. F.; Radha, P. B.; Regan, S. P.; Sangster, T. C.; Froula, D. H.

    2016-05-01

    The angularly resolved mass ablation rates and ablation-front trajectories for Si-coated CH targets were measured in direct-drive inertial confinement fusion experiments to quantify cross-beam energy transfer (CBET) while constraining the hydrodynamic coupling. A polar-direct-drive laser configuration, where the equatorial laser beams were dropped and the polar beams were repointed from a symmetric direct-drive configuration, was used to limit CBET at the pole while allowing it to persist at the equator. The combination of low- and high-CBET conditions observed in the same implosion allowed for the effects of CBET on the ablation rate and ablation pressure to be determined. Hydrodynamic simulations performed without CBET agreed with the measured ablation rate and ablation-front trajectory at the pole of the target, confirming that the CBET effects on the pole are small. The simulated mass ablation rates and ablation-front trajectories were in excellent agreement with the measurements at all angles when a CBET model based on Randall's equations [C. J. Randall et al., Phys. Fluids 24, 1474 (1981)] was included into the simulations with a multiplier on the CBET gain factor. These measurements were performed on OMEGA and at the National Ignition Facility to access a wide range of plasma conditions, laser intensities, and laser beam geometries. The presence of the CBET gain multiplier required to match the data in all of the configurations tested suggests that additional physics effects, such as intensity variations caused by diffraction, polarization effects, or shortcomings of extending the 1-D Randall model to 3-D, should be explored to explain the differences in observed and predicted drive.

  3. Evolution of ring current formed by relativistic electron beam injection into a charge but not current neutralizing plasma

    International Nuclear Information System (INIS)

    The time evolutions of the azimuthal momentum distribution of the axisymmetrically injected electrons and the resulting ring current are self-consistently analyzed under the assumption that no return current is induced in the background plasma. It is shown that the ring current grows linearly with time for a characteristic time from the start of beam injection, and afterthere it tends to saturate at some level. The dependence of the time evolution of the ring current on the beam energy at injection and on the injection current is also obtained. (author)

  4. Lower hybrid current drive experiments on the MIT Alcator C and Versator II tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Knowlton, S.; McDermott, S.; Porkolab, M.; Takase, Y.; Texter, S.; Bonoli, P.; Fiore, C.; McCool, S.; Mayberry, M.; Chen, K.I.

    1985-08-01

    Energy confinement studies in lower hybrid RF driven discharges at 4.6 GHz have been carried out on the Alcator C tokamak. The electron temperature profile is measured by a five point Thomson scattering system and the ion temperature by charge-exchange analysis. The energy content of the bulk plasma is found to be similar for RF-driven and ohmic discharges of identical current and density. In the parameter range anti n/sub e/ = 3 - 7 x 10/sup 13/ cm/sup -3/, B = 7 - 11 T, I/sub p/ = 100 - 200 kA, q (a) > 8, the RF power needed to sustain the discharge is significantly greater than the ohmic power required to maintain a similar plasma. The gross energy confinement time is lower in the RF-driven discharges than in the ohmic ones by a factor of 1.5 to 4, depending on plasma conditions. The frequency scaling of the density limit for current drive is reported from the Versator II tokamak. The steady-state current drive density limit of anti n/sub e/ = 6 x 10/sup 12/ cm/sup -3/ at 800 MHz. has been raised to a density of at least anti n/sub e/ = 1.0 x 10/sup 13/ cm/sup -3/ at the same toroidal field by operations at a frequency of 2.45 GHz. Superthermal electron effects during RF injection are observed up to a density of anti n/sub e/ = 2.5 x 10/sup 13/ cm/sup -3/.

  5. High power lower hybrid current drive experiment in TORE SUPRA tokamak

    International Nuclear Information System (INIS)

    A review of the Lower Hybrid (LH) current drive experiments carried out on the TORE SUPRA tokamak is presented. This work highlights the issues for an effective application of the LH wave at high power in reactor relevant conditions. Very promising performances have been obtained with the new launcher that is designed to couple up to 4 MW during 1000 s at a power density of 25 MWm-2. The heat load on the guard limiter of the antenna and the fast electron acceleration in the near electric field of the grill mouth remain at a low level, while the mean reflection coefficient never exceeds 10%. The powerful diagnosis capabilities of the hard x-ray (HXR) fast electron bremsstrahlung tomography has led to significant progresses in the understanding of the LH wave dynamics. The role of the fastest electrons driven by the LH wave is clearly identified. From HXR measurements, an increase of the LH current drive efficiency with the plasma current is predicted and confirmed by a direct determination at zero loop voltage. LH power absorption is observed to be off-axis in almost all plasma conditions, and its radial width clearly depends of antenna phasing conditions. A correlation between the HXR profiles and the onset of an improved core confinement is identified in fully non-inductive discharges. This regime ascribed to some vanishing of the magnetic shear is found to be transient and usually ends when the minimum of the safety factor becomes very close to 2, leading to a large MHD activity. Experimental observations and numerical simulations suggest that LH power is absorbed in a few number of passes. However, besides toroidal mode coupling, additional mechanisms may likely contribute to a spectral broadening to the LH wave. (author)

  6. Controlling fluctuations and transport in the reversed field pinch with edge current drive and plasma biasing

    International Nuclear Information System (INIS)

    Two techniques are employed in the Madison Symmetric Torus (MST) to test and control different aspects of fluctuation induced transport in the Reversed Field Pinch (RFP). Auxiliary edge currents are driven along the magnetic field to modify magnetic fluctuations, and the particle and energy transport associated with them. In addition, strong edge flows are produced by plasma biasing. Their effect on electrostatic fluctuations and the associated particle losses is studied. Both techniques are accomplished using miniature insertable plasma sources that are biased negatively to inject electrons. This type of emissive electrode is shown to reliably produce intense, directional current without significant contamination by impurities. The two most important conclusions derived from these studies are that the collective modes resonant at the reversal surface play a role in global plasma confinement, and that these modes can be controlled by modifying the parallel current profile outside of the reversal surface. This confirms predictions based on magnetohydrodynamic (MHD) simulations that auxiliary current drive in the sense to flatten the parallel current profile can be successful in controlling magnetic fluctuations in the RFP. However, these studies expand the group of magnetic modes believed to cause transport in MST and suggest that current profile control efforts need to address both the core resonant magnetic modes and those resonant at the reversal surface. The core resonant modes are not significantly altered in these experiments; however, the distribution and/or amplitude of the injected current is probably not optimal for affecting these modes. Plasma biasing generates strong edge flows with shear and particle confinement likely improves in these discharges. These experiments resemble biased H modes in other magnetic configurations in many ways. The similarities are likely due to the common role of electrostatic fluctuations in edge transport

  7. Controlling fluctuations and transport in the reversed field pinch with edge current drive and plasma biasing

    Energy Technology Data Exchange (ETDEWEB)

    Craig, D.J.G.

    1998-09-01

    Two techniques are employed in the Madison Symmetric Torus (MST) to test and control different aspects of fluctuation induced transport in the Reversed Field Pinch (RFP). Auxiliary edge currents are driven along the magnetic field to modify magnetic fluctuations, and the particle and energy transport associated with them. In addition, strong edge flows are produced by plasma biasing. Their effect on electrostatic fluctuations and the associated particle losses is studied. Both techniques are accomplished using miniature insertable plasma sources that are biased negatively to inject electrons. This type of emissive electrode is shown to reliably produce intense, directional current without significant contamination by impurities. The two most important conclusions derived from these studies are that the collective modes resonant at the reversal surface play a role in global plasma confinement, and that these modes can be controlled by modifying the parallel current profile outside of the reversal surface. This confirms predictions based on magnetohydrodynamic (MHD) simulations that auxiliary current drive in the sense to flatten the parallel current profile can be successful in controlling magnetic fluctuations in the RFP. However, these studies expand the group of magnetic modes believed to cause transport in MST and suggest that current profile control efforts need to address both the core resonant magnetic modes and those resonant at the reversal surface. The core resonant modes are not significantly altered in these experiments; however, the distribution and/or amplitude of the injected current is probably not optimal for affecting these modes. Plasma biasing generates strong edge flows with shear and particle confinement likely improves in these discharges. These experiments resemble biased H modes in other magnetic configurations in many ways. The similarities are likely due to the common role of electrostatic fluctuations in edge transport.

  8. Electron cyclotron current drive predictions for ITER: Comparison of different models

    International Nuclear Information System (INIS)

    Full text: Due to its high localization and operational flexibility, Electron Cyclotron Current Drive (ECCD) is envisaged for stabilizing the Neoclassical Tearing Mode (NTM) in tokamaks and correcting the rotational transform profile in stellarators. While the spatial location of the electron cyclotron resonant interaction is usually calculated by the ray-tracing technique, numerical tools for calculating the ECCD efficiency are not so common. Two different methods are often applied: i) direct calculation by Fokker-Planck modelling, and ii) by the adjoint approach technique. In the present report we analyze and compare different models used in the adjoint approach technique from the point of view of ITER applications. The numerical tools for calculating the ECCD efficiency developed to date do not completely cover the range of collisional regimes for the electrons involved in the current drive. Only two opposite limits are well developed, collisional and collisionless. Nevertheless, for the densities and temperatures expected for ECCD application in ITER, the collisionless limit model (with trapped particles taken into account) is quite suitable. We analyze the requisite ECCD scenarios with help of the new ray tracing code TRAVIS with the adjoint approach implemented. The (adjoint) Green's function applied for the current drive calculations is formulated with momentum conservation taken into account; this is especially important and even crucial for scenarios, in which mainly bulk electrons are responsible for absorption of the RF power. For comparison, the most common 'high speed limit' model in which the collision operator neglects the integral part and which is approximated by terms valid only for the tail electrons, produces an ECCD efficiency which is an underestimate for some cases by a factor of about 2. In order to select the appropriate model, a rough criterion of 'high speed limit' model applicability is formulated. The results are verified also by

  9. Predictive Pulse Pattern Current Modulation Scheme for Harmonic Reduction in Three-Phase Multi-Drive Systems

    DEFF Research Database (Denmark)

    Davari, Pooya; Yang, Yongheng; Zare, Firuz; Blaabjerg, Frede

    2016-01-01

    The majority of the industrial motor drive systems are equipped with the conventional line-commutated front-end rectifiers, and being one of the main sources of harmonics in the power line. While a parallel combination of these drive units elevates current quality issues, a proper arrangement of...... them can lead to the cancellation of specific harmonics. This paper proposes a new cost-effective harmonic mitigation solution for multi-drive systems using a predictive pulse pattern current modulation control strategy. The proposed technique applies suitable interaction among parallel drive units at...... the rectification stage to synthesize sinusoidal input currents. The input voltage sensing is avoided in order to minimize the number of required sensors, and the grid synchronization also has been implemented based on a common Phase-Locked-Loop (PLL) using the DC-link capacitor voltage ripple...

  10. Complete stabilization of neoclassical tearing modes with lower hybrid current drive on COMPASS-D. RF teams.

    Science.gov (United States)

    Warrick, C D; Buttery, R J; Cunningham, G; Fielding, S J; Hender, T C; Lloyd, B; Morris, A W; O'Brien, M R; Pinfold, T; Stammers, K; Valovic, M; Walsh, M; Wilson, H R

    2000-07-17

    Lower hybrid current drive (LHCD) with modest powers ( approximately 10% of the total power input) has been used for the first time to completely stabilize performance limiting neoclassical tearing modes in many COMPASS-D tokamak discharges. The stabilizing effect in these experiments is consistent with a reduction in the free energy available in the current profile to drive tearing modes (i.e., the stability index, delta(')) resulting from favorable current gradients (from the LHCD driven current) around the rational surface. PMID:10991343

  11. Status of the ITER Electron Cyclotron Heating and Current Drive System

    Science.gov (United States)

    Darbos, Caroline; Albajar, Ferran; Bonicelli, Tullio; Carannante, Giuseppe; Cavinato, Mario; Cismondi, Fabio; Denisov, Grigory; Farina, Daniela; Gagliardi, Mario; Gandini, Franco; Gassmann, Thibault; Goodman, Timothy; Hanson, Gregory; Henderson, Mark A.; Kajiwara, Ken; McElhaney, Karen; Nousiainen, Risto; Oda, Yasuhisa; Omori, Toshimichi; Oustinov, Alexander; Parmar, Darshankumar; Popov, Vladimir L.; Purohit, Dharmesh; Rao, Shambhu Laxmikanth; Rasmussen, David; Rathod, Vipal; Ronden, Dennis M. S.; Saibene, Gabriella; Sakamoto, Keishi; Sartori, Filippo; Scherer, Theo; Singh, Narinder Pal; Strauß, Dirk; Takahashi, Koji

    2016-01-01

    The electron cyclotron (EC) heating and current drive (H&CD) system developed for the ITER is made of 12 sets of high-voltage power supplies feeding 24 gyrotrons connected through 24 transmission lines (TL), to five launchers, four located in upper ports and one at the equatorial level. Nearly all procurements are in-kind, following general ITER philosophy, and will come from Europe, India, Japan, Russia and the USA. The full system is designed to couple to the plasma 20 MW among the 24 MW generated power, at the frequency of 170 GHz, for various physics applications such as plasma start-up, central H&CD and magnetohydrodynamic (MHD) activity control. The design takes present day technology and extends toward high-power continuous operation, which represents a large step forward as compared to the present state of the art. The ITER EC system will be a stepping stone to future EC systems for DEMO and beyond.

  12. Theory of the anomalous doppler instability during lower-hybrid current drive

    International Nuclear Information System (INIS)

    An instability condition is derived for electrostatic waves obeying the dispersion relation ω = ω/sub p//sub e/k/sub parallel//k using a two dimensional electron distribution function, f(v/sub parallel/,v/sub perpendicular/), appropriate for lower-hybrid current drive. It is found that when the raised plateau in f in the velocity range v12 has a sufficiently large anisotropy, T/sub p//sub parallel/>T/sub p//sub perpendicular/, this mode can become unstable. If the plateau velocities satisfy the condition v2/v1>1+ω/sub c//sub e//ω/sub p//sub e/ then waves exist with phase velocities in the plateau region and these waves are most easily destabilized by the anomalous doppler resonance, ω-k/sub parallel/v/sub parallel/ = -ω/sub c//sub e/

  13. Determination of the energy of suprathermal electrons during lower hybrid current drive on PBX-M

    International Nuclear Information System (INIS)

    Suprathermal electrons are diagnosed by a hard x-ray pinhole camera during lower hybrid current drive on PBX-M. The experimental hard x-ray images are compared with simulated images, which result from an integration of the relativistic bremsstrahlung along lines-of-sight through the bean-shaped plasma. Images with centrally peaked and radially hollow radiation profiles are easily distinguished. The energy distribution of the suprathermal electrons is analyzed by comparing images taken with different absorber foils. An effective photon temperature is derived from the experimental images, and a comparison with simulated photon temperatures yields the energy of the suprathermal electrons. The analysis indicates that the energy of the suprathermal electrons in the hollow discharges is in the 50 to 100 key range in the center of the discharge. There seems to exist a very small higher energy component close to the plasma edge

  14. Combined repetitive pellet injection and lower hybrid current drive experiments in Tore Supra

    International Nuclear Information System (INIS)

    In order to control the plasma density during long shots (>10-20s), attempts to combine repetitive pellet fuelling and lower hybrid current drive have been carried out in Tore Supra. As expected from previous studies, the penetration of pellets injected during LH pulses is small and corresponds to a poor fuelling efficiency. Nevertheless, a partial recovery of the penetration depth is obtained by switching off the LH power just before each injection, which yields a significant increase of the fuelling efficiency. This difference in the pellet penetrations is interpreted in the frame of an ablation model taking into account the heating in volume of the pellet by the fast electron tail. (author) 5 refs., 4 figs

  15. Comments on edge turbulence during lower hybrid current drive experiment on CASTOR tokamak

    International Nuclear Information System (INIS)

    Edge plasma electrostatic turbulence is discussed from the point of view of its role in inducing anomalous particle transport. Preliminary results are presented of plasma edge fluctuation measurements obtained in the CASTOR tokamak by using the Langmuir probe technique. The level of edge turbulence found is sufficiently high to explain the anomalous particle losses observed in the ohmic heting regime of the tokamak discharge. On the other hand, it decreases appreciably during the combined lower hybrid current drive and ohmic heating regimes, the particle confinement time simultaneously increasing about twice. Thus, the fluctuation induced transport seems to be responsible for the anomalous particle transport in the CASTOR tokamak. (J.U.). 10 figs., 26 refs

  16. A Study on New Current Controller for 7-Phase BLDC Motor Drive System

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Surk; Jeon, Ywun Seok; Mok, Hyung Soo [Konkuk University (Korea); Kim, Duk Keun [Komotek Co., Ltd. (Korea)

    2001-04-01

    Recently, the demand of motor for industrial, household machinery is increasing. As Switching devices and control technology are progressing, so the use of BLDC Motor is increasing. But 3-phase BLCD Motor generally used has pulsating torque and speed variation in commutation, so the range of its application is limited to high speed operation. Especially, to solve these problems, it is necessary to increase phase of Motor, so study of Poly-Phase BLDC Motor is progressing. However, when hysteresis current controller is used, switching frequency is highly increasing. In this paper, 7-Phase BLDC Motor drive system is designed. Also MSTC (Minimum Switching Time Controller) is proposed and with simulation and experiment, their validities are verified. (author). 10 refs., 26 figs., 1 tab.

  17. Lower hybrid and Electron Bernstein Wave current drive experiments in MST

    International Nuclear Information System (INIS)

    Inductive current profile modification in MST has been successful in reducing fluctuations and transport but is transient and radially non-localized. Current profile control with rf waves offers steady and more precise control. Studies of lower hybrid (LH) wave and electron Bernstein wave (EBW) injection are underway. This first application of LH waves to the high dielectric RFP presents challenges in rf physics, e.g., limited wave accessibility. The novel interdigital line antenna, chosen because of stringent vacuum vessel constraints, operates at 800 MHz and nparallel ∼ 7.5 parameters chosen to drive current in the edge (r/a ∼ 0.8) with strong single-pass absorption. Extensive antenna loading studies have been performed to validate the design up to the present source power limit of 225 kW with up to 125 kW being coupled to the plasma. Hard-x-ray emission with energies as high as 50 keV has been observed. The emission is spatially localized to the antenna location with a toroidal spread of about 60 degrees. This interesting toroidal localization of the emission that occurs in the dominantly poloidal magnetic field of the RFP could result from the formation of a localized current structure. Presently, a 250 kW system designed to heat electrons and drive current via the electron Bernstein wave is in operation on the MST reversed field pinch. The antenna is a grill of four half-height S-band waveguides with each arm powered by a separate, phase controlled traveling wave tube amplifier at 3.6 GHz. The X-mode polarization is being used to launch electromagnetic waves that mode convert to EBWs in the edge plasma. Coupling to the plasma (as measured by the reflected power ratio) is dependent on the relative phasing between adjacent waveguides. The total reflected power can be maintained near the 10% level. The antenna face is outfitted with a pair of triple Langmuir probes to measure local electron density; the density gradient at the upper hybrid resonance

  18. Influence of driving frequency on discharge modes in a dielectric-barrier discharge with multiple current pulses

    International Nuclear Information System (INIS)

    A one-dimensional self-consistent fluid model was employed to investigate the effect of the driving frequency on the discharge modes in atmospheric-pressure argon discharge with multiple current pulses. The discharge mode was discussed in detail not only at current peaks but also between two adjacent peaks. The simulation results show that different transitions between the Townsend and glow modes during the discharge take place with the driving frequency increased. A complicated transition from the Townsend mode, through glow, Townsend, and glow, and finally back to the Townsend one is found in the discharge with the driving frequency of 8 kHz. There is a tendency of transition from the Townsend to glow mode for the discharge both at the current peaks and troughs with the increasing frequency. The discharge in the half period can all along operate in the glow mode with the driving frequency high enough. This is resulted from the preservation of more electrons in the gas gap and acquisition of more electron energy from the swiftly varying electric field with the increase in driving frequency. Comparison of the spatial and temporal evolutions of the electron density at different driving frequencies indicates that the increment of the driving frequency allows the plasma chemistry to be enhanced. This electrical characteristic is important for the applications, such as surface treatment and biomedical sterilization

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Swanekamp, S. B.; Angus, J. R.; Cooperstein, G.; Ottinger, P. F.; Richardson, A. S.; Schumer, J. W.; Weber, B. V. [Plasma Physics Division, Naval Research Laboratory, Washington, District of Columbia 20375 (United States)

    2015-11-15

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

  1. Numerical simulation of high-current ion linear induction accelerator with additional electron beam injection

    International Nuclear Information System (INIS)

    The 2d3v particle-in-cell simulations of the transportation and acceleration of a high-current tubular ion beam through six magnetoinsulated accelerating gaps are presented. Charge and current compensations are carried out by an accompanying electron beam, and also by additionally injected electron beams. The accelerating electric field is enclosed to the first, third and fifth cusps. Its magnitudes are those, that initial kinetic energy of compensating electron beams is little bit higher than a potential barrier of an accelerating field in each cusp, that allows an electron beam to overcome accelerating potential in one cusp. The second, fourth and sixth cusps in which the accelerating field is absent, are used for injection of additional compensating electron beams which replace the electron beam which has 'worked-out' on the previous accelerating gap. The simulations involve solving a complete set of Maxwell's equations with charge-conserving scheme for calculating the current density on a mesh, and relativistic motion equations for charged particles. The possibility of transporting and acceleration of a high-current tubular ion beam in six cusps is shown. It is shown, that distribution function of a high-current ion beam on an output of the accelerator essentially improves due to optimization of parameters of additionally injected electron beams.

  2. A DEMO relevant fast wave current drive high harmonic antenna exploiting the high impedance technique

    Science.gov (United States)

    Milanesio, D.; Maggiora, R.

    2015-12-01

    Ion Cyclotron (IC) antennas are routinely adopted in most of the existing nuclear fusion experiments, even though their main goal, i.e. to couple high power to the plasma (MW), is often limited by rather severe drawbacks due to high fields on the antenna itself and on the unmatched part of the feeding lines. In addition to the well exploited auxiliary ion heating during the start-up phase, some non-ohmic current drive (CD) at the IC range of frequencies may be explored in view of the DEMO reactor. In this work, we suggest and describe a compact high frequency DEMO relevant antenna, based on the high impedance surfaces concept. High-impedance surfaces are periodic metallic structures (patches) usually displaced on top of a dielectric substrate and grounded by means of vertical posts embedded inside the dielectric, in a mushroom-like shape. These structures present a high impedance, within a given frequency band, such that the image currents are in-phase with the currents of the antenna itself, thus determining a significant efficiency increase. After a general introduction on the properties of high impedance surfaces, we analyze, by means of numerical codes, a dielectric based and a full metal solution optimized to be tested and benchmarked on the FTU experiment fed with generators at 433MHz.

  3. A DEMO relevant fast wave current drive high harmonic antenna exploiting the high impedance technique

    Energy Technology Data Exchange (ETDEWEB)

    Milanesio, D., E-mail: daniele.milanesio@polito.it; Maggiora, R. [Politecnico di Torino, Dipartimento di Elettronica e Telecomunicazioni (DET), Torino (Italy)

    2015-12-10

    Ion Cyclotron (IC) antennas are routinely adopted in most of the existing nuclear fusion experiments, even though their main goal, i.e. to couple high power to the plasma (MW), is often limited by rather severe drawbacks due to high fields on the antenna itself and on the unmatched part of the feeding lines. In addition to the well exploited auxiliary ion heating during the start-up phase, some non-ohmic current drive (CD) at the IC range of frequencies may be explored in view of the DEMO reactor. In this work, we suggest and describe a compact high frequency DEMO relevant antenna, based on the high impedance surfaces concept. High-impedance surfaces are periodic metallic structures (patches) usually displaced on top of a dielectric substrate and grounded by means of vertical posts embedded inside the dielectric, in a mushroom-like shape. These structures present a high impedance, within a given frequency band, such that the image currents are in-phase with the currents of the antenna itself, thus determining a significant efficiency increase. After a general introduction on the properties of high impedance surfaces, we analyze, by means of numerical codes, a dielectric based and a full metal solution optimized to be tested and benchmarked on the FTU experiment fed with generators at 433MHz.

  4. Highly localized electron cyclotron heating and current drive and improved core transport in DIII-D

    International Nuclear Information System (INIS)

    Electron cyclotron heating (ECH) and current drive (ECCD) are widely recognized as methods of depositing highly localized power and current in a plasma, based on calculations of wave absorption. The experiments reported here demonstrate through direct analysis of the poloidal field pitch angles measured by the motional Stark effect diagnostic that ECCD can be as localized as theory predicts. This very narrow profile of driven current has been verified even for ELMing H-mode discharges, and observation of full stabilization of neoclassical tearing modes tends to corroborate the calculations of ECCD far off axis even in plasmas with large MHD activity present. The electron heating by EC waves can have dramatic effects on the plasma, creating high central electron temperatures even with very modest ECH power and generating a strong transport barrier in the electron fluid in discharges with strongly reversed central magnetic shear. The electron diffusivity is much smaller than ion neoclassical diffusivity in the narrow barrier which develops just outside the heating location. (author)

  5. Advanced antenna system for Alfven wave plasma heating and current drive in TCABR tokamak

    International Nuclear Information System (INIS)

    An advanced antenna system that has been developed for investigation of Alfven wave plasma heating and current drive in the TCABR tokamak is described. The main goal was the development of such a system that could insure the excitation of travelling single helicity modes with predefined wave mode numbers M and N. The system consists of four similar modules with poloidal windings. The required spatial spectrum is formed by proper phasing of the RF feeding currents. The impedance matching of the antenna with the four-phase oscillator is accomplished by resonant circuits which form one assembly unit with the RF feeders. The characteristics of the antenna system design with respect to the antenna-plasma coupling and plasma wave excitation, for different phasing of the feeding currents, are summarised. The antenna complex impedance Z=ZR+ZI is calculated taking into account both the plasma response to resonant excitation of fast Alfven waves and the nonresonant excitation of vacuum magnetic fields in conducting shell. The matching of the RF generator with the antenna system during plasma heating is simulated numerically, modelling the plasma response with mutually coupled effective inductances with corresponding active ZR and reactive ZI impedances. The results of the numerical simulation of the RF system performance, including both the RF magnetic field spectrum analysis and the modeling of the RF generator operation with plasma load, are presented. (orig.)

  6. A DEMO relevant fast wave current drive high harmonic antenna exploiting the high impedance technique

    International Nuclear Information System (INIS)

    Ion Cyclotron (IC) antennas are routinely adopted in most of the existing nuclear fusion experiments, even though their main goal, i.e. to couple high power to the plasma (MW), is often limited by rather severe drawbacks due to high fields on the antenna itself and on the unmatched part of the feeding lines. In addition to the well exploited auxiliary ion heating during the start-up phase, some non-ohmic current drive (CD) at the IC range of frequencies may be explored in view of the DEMO reactor. In this work, we suggest and describe a compact high frequency DEMO relevant antenna, based on the high impedance surfaces concept. High-impedance surfaces are periodic metallic structures (patches) usually displaced on top of a dielectric substrate and grounded by means of vertical posts embedded inside the dielectric, in a mushroom-like shape. These structures present a high impedance, within a given frequency band, such that the image currents are in-phase with the currents of the antenna itself, thus determining a significant efficiency increase. After a general introduction on the properties of high impedance surfaces, we analyze, by means of numerical codes, a dielectric based and a full metal solution optimized to be tested and benchmarked on the FTU experiment fed with generators at 433MHz

  7. Fault diagnosis of motor drives using stator current signal analysis based on dynamic time warping

    Science.gov (United States)

    Zhen, D.; Wang, T.; Gu, F.; Ball, A. D.

    2013-01-01

    Electrical motor stator current signals have been widely used to monitor the condition of induction machines and their downstream mechanical equipment. The key technique used for current signal analysis is based on Fourier transform (FT) to extract weak fault sideband components from signals predominated with supply frequency component and its higher order harmonics. However, the FT based method has limitations such as spectral leakage and aliasing, leading to significant errors in estimating the sideband components. Therefore, this paper presents the use of dynamic time warping (DTW) to process the motor current signals for detecting and quantifying common faults in a downstream two-stage reciprocating compressor. DTW is a time domain based method and its algorithm is simple and easy to be embedded into real-time devices. In this study DTW is used to suppress the supply frequency component and highlight the sideband components based on the introduction of a reference signal which has the same frequency component as that of the supply power. Moreover, a sliding window is designed to process the raw signal using DTW frame by frame for effective calculation. Based on the proposed method, the stator current signals measured from the compressor induced with different common faults and under different loads are analysed for fault diagnosis. Results show that DTW based on residual signal analysis through the introduction of a reference signal allows the supply components to be suppressed well so that the fault related sideband components are highlighted for obtaining accurate fault detection and diagnosis results. In particular, the root mean square (RMS) values of the residual signal can indicate the differences between the healthy case and different faults under varying discharge pressures. It provides an effective and easy approach to the analysis of motor current signals for better fault diagnosis of the downstream mechanical equipment of motor drives in the time

  8. Automated pinhole-aperture diagnostic for the current profiling of TWT electron beams

    International Nuclear Information System (INIS)

    The measurement system reported here is intended for use in determining the current density distribution of electron beams from Pierce guns for use in TWTs. The system was designed to automatically scan the cross section of the electron beam and collect the high-resolution data with a Faraday cup probe mounted on a multistage manipulator using the LabVIEW program. A 0.06 mm thick molybdenum plate with a pinhole and a Faraday cup mounted as a probe assembly was employed to sample the electron beam current with 0.5 µm space resolution. The thermal analysis of the probe with pulse beam heating was discussed. A 0.45 µP electron gun with the expected minimum beam radius 0.42 mm was measured and the three-dimensional current density distribution, beam envelope and phase space were presented. (paper)

  9. 3D Fokker-Planck calculation of combined fast wave/lower hybrid and electron cyclotron current drive in tokamaks

    International Nuclear Information System (INIS)

    In a non-reactor tokamak environment, lower hybrid current drive can be combined with electron cyclotron waves, both (1) to control the radial profile of LH current deposition, and (2) to enhance the current drive efficiency. A related rf synergy is the use of multiple LH spectra for radial profile control as demonstrated in the ASDEX tokamak. In a reactor environment, fast waves provide an appropriate primary current drive system which can penetrate radially to the plasma core, and can be combined with ECCD. We use the CQL3D Fokker-Planck code to study these processes. Modelings of LHCD radial profile control by ''filling the spectral gap'' with EC or with additional LH power are presented. In the reactor environment, a range of cases with combined fast wave and electron cyclotron waves are examined, but no useful synergisms are found

  10. Quasi-linear modeling of lower hybrid current drive in ITER and DEMO

    Science.gov (United States)

    Cardinali, A.; Cesario, R.; Panaccione, L.; Santini, F.; Amicucci, L.; Castaldo, C.; Ceccuzzi, S.; Mirizzi, F.; Tuccillo, A. A.

    2015-12-01

    First pass absorption of the Lower Hybrid waves in thermonuclear devices like ITER and DEMO is modeled by coupling the ray tracing equations with the quasi-linear evolution of the electron distribution function in 2D velocity space. As usually assumed, the Lower Hybrid Current Drive is not effective in a plasma of a tokamak fusion reactor, owing to the accessibility condition which, depending on the density, restricts the parallel wavenumber to values greater than n∥crit and, at the same time, to the high electron temperature that would enhance the wave absorption and then restricts the RF power deposition to the very periphery of the plasma column (near the separatrix). In this work, by extensively using the "raystar" code, a parametric study of the propagation and absorption of the LH wave as function of the coupled wave spectrum (as its width, and peak value), has been performed very accurately. Such a careful investigation aims at controlling the power deposition layer possibly in the external half radius of the plasma, thus providing a valuable aid to the solution of how to control the plasma current profile in a toroidal magnetic configuration, and how to help the suppression of MHD mode that can develop in the outer part of the plasma. This analysis is useful not only for exploring the possibility of profile control of a pulsed operation reactor as well as the tearing mode stabilization, but also in order to reconsider the feasibility of steady state regime for DEMO.

  11. High precision electron beam diagnostic system for high current long pulse beams

    International Nuclear Information System (INIS)

    As part of the effort to develop a multi-axis electron beam transport system using stripline kicker technology for DARHT II applications, it is necessary to precisely determine the position and extent of long high energy beams (6-40 MeV, 1-4 kA, 2 microseconds) for accurate position control. The kicker positioning system utilizes shot-to-shot adjustments for reduction of relatively slow (<20 MHz) motion of the beam centroid. The electron beams passing through the diagnostic systems have the potential for large halo effects that tend to corrupt measurements performed using capacitive pick-off probes. Likewise, transmission line traveling wave probes have problems with multi-bounce effects due to these longer pulse widths. Finally, the high energy densities experienced in these applications distort typical foil beam position measurements

  12. Current status of electron beam processing system and its applications

    International Nuclear Information System (INIS)

    The feature and application fields of electron beam processing systems (EPS), the selection of machine ratings and safety measures for EPS are described. EPS has the various features: a) Chemical reactions occurs independent of the temperature, b) it occurs without any added substances such as catalysts, c) mass productivity, d) easy operation, as is exemplified by switch ON and OFF, and e) easy maintenance, compared with radioisotope sources. After briefly explaining acceleration type (DC or AC), power supply (Van-de-Graaf or Cockcroft-walton and others), beam scanning to be used for large area irradiation, and some typical applications (cross-linking, radical polymerization, the paper describes necessary safety measures such as X-ray shielding, ozone control including ozone generation and its disposal, interlock system, warning buzzer, and monitoring and measuring. (S. Ohno)

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

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yongjian, E-mail: yjxu@ipp.ac.cn; Hu, Chundong; Xie, Yuanlai; Liu, Zhimin; Xie, Yahong; Liu, Sheng; Liang, Lizheng; Jiang, Caichao; Sheng, Peng; Yu, Ling

    2015-09-21

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

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

    Science.gov (United States)

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

    2015-09-01

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

  15. Self-consistent quasi-linear modelling of Lower Hybrid Current Drive in ITER and DEMO

    International Nuclear Information System (INIS)

    First pass absorption of the Lower Hybrid waves in thermonuclear devices like ITER and DEMO is modelled by coupling the ray tracing equations for the wave phase and amplitude with the quasi-linear evolution of the electron distribution function. A system of coupled ordinary differential equations for each Fourier component of the spectrum radiated by the LH antenna is derived and solved when considering both 1D/2D Fokker-Planck model for the electron distribution function. This allows to reconstruct and to evolve the quasi-linear diffusion coefficient consistently with the wave propagation, to calculate the power deposition profile and the amount of current driven by the wave. As usually assumed, the Lower Hybrid Current Drive is not effective in a plasma of a tokamak fusion reactor like ITER or DEMO, because the high electron temperature would enhance the wave absorption and then limit the RF power deposition to the very periphery of the plasma column (near the separatrix). In this work by extensively using this self-consistent modelling for the propagation and absorption of the LH wave, a parametric study on the wave spectrum (and consequently on the antenna design) as spectrum width, peak value, secondary lobes etc. has been performed very accurately. Such a careful investigation aims at controlling the power deposition layer possibly in the external half radius of the plasma, thus providing a valuable aid to the solution of how to control the plasma current profile in a toroidal magnetic configuration. This analysis is useful not only for exploring the possibility of profile control of a pulsed operation reactor, but also in order to reconsider the feasibility of steady state regime

  16. Beam instability during high-current heavy-ion beam transport

    International Nuclear Information System (INIS)

    In driver system for heavy ion inertial fusion, beam dynamics is investigated by particle-in-cell simulations during final beam bunching. The particle simulations predict that the beam is transported with the localized transverse charge distribution induced by the strong space charge effect. The calculation results also show that the emittance growth during the longitudinal bunch compression for various particle distributions at the initial conditions and with two types of transverse focusing model, which are a continuous focusing and an alternating gradient focusing lattice configurations. (author)

  17. Klystron beam bunching

    International Nuclear Information System (INIS)

    A detailed description of electron-beam bunching phenomena in klystrons is presented. Beam harmonic current is defined, both space-charge and ballistic bunching are analyzed, Ramo's theorem is used to describe how a bunched beam drives a cavity, and a general cavity model including external coupling is provided. (author)

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

    Science.gov (United States)

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

    2009-01-01

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

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

    International Nuclear Information System (INIS)

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

  20. Beam smoothing and temporal effects: optimized preparation of laser beams for direct-drive inertial confinement fusion

    International Nuclear Information System (INIS)

    Direct-drive laser fusion received a number of setbacks from the experimental observation in the 1960s and 1970s of very complex interactions in laser plasma experiments caused by a number of nonlinear and anomalous phenomena. Although smoothing methods were introduced intuitively or empirically -succeeding in reducing these difficulties - it was not until a few years ago that the 20-ps stochastic pulsation mechanism was discovered. We assume here that this 20 ps stochastic pulsation may be the major obstacle to achieving direct-drive fusion, even though it is now generally assumed that the major challenge to the achievement of direct-drive fusion is the Rayleigh-Taylor instability. While we do not discount the importance of the Rayleigh-Taylor mechanisms, we concentrate here on the analysis of the pulsation process. A method of analysis was developed, using, time-dependent real-time computations employing a genuine two-fluid model, which includes the interior electric fields and the very large amplitude longitudinal plasma oscillations that are driven by the laser field. These mechanisms, which were first suggested in 1974, reveal themselves now as self-generated von-Laue gratings, preventing the propagation of laser radiation through the outermost plasma corona and preventing energy deposition by temporal interuption caused by thermal relaxation and the subsequent reestablishment of these gratings, and so on. The abolition of this pulsation by broad-band laser irradiation or other smoothing methods is now well understood. A synopsis of these developments is presented here consistent with Rubbia's proposition of using the MJ drivers for laser fusion, the technology for which is now available. (author)

  1. Transient transport experiments in the current-drive experiment upgrade spherical torus

    International Nuclear Information System (INIS)

    Electron transport has been measured in the Current-Drive Experiment Upgrade (CDX-U) (T. Jones, Ph.D. thesis, Princeton University, 1995) using two separate perturbative techniques. Sawteeth at the q=1 radius (r/a∼0.15) induced outward-propagating heat pulses, providing time-of-flight information leading to a determination of χe as a function of radius. Gas modulation at the plasma edge introduced inward-propagating cold pulses, providing a complementary time-of-flight based χe profile measurement. This work represents the first localized measurement of χe in a spherical torus. Core (r/ae values from the sawtooth study are 1-2 m2/s, and from the gas modulation study are 1-6 m2/s, increasing by an order of magnitude or more outside of the core region. Furthermore, the χe profile exhibits a sharp transition near r/a=1/3. Spectral and profile analyses of the soft x-rays, scanning interferometer, and edge probe data show no evidence of a significant magnetic island causing the high χe region. Comparisons are performed to several theoretical models, with measured χe≅5-10x neoclassical estimates in the core

  2. Electron cyclotron absorption measurements in Tore-Supra during lower hybrid current drive

    International Nuclear Information System (INIS)

    A transmission diagnostic system working in the frequency range 77-109 GHz has been implemented in the Tore Supra tokamak. It makes use of an ordinary mode launched along a vertical diameter, i.e, propagating along a nearly constant magnetic field. A modulation of the incident power allows to increase the signal to noise ratio. The purpose of the diagnostic is to measure electron cyclotron absorption (ECA) below the electron cyclotron frequency fc in the presence of the fast electron tails created during lower-hybrid current drive. As is known, for a parallel electron tail, the absorption coefficient at fc is proportional to the parallel distribution function and a frequency scan yields, in principle the shape of the parallel distribution as a function of the parallel momentum. The main advantages of ECA with respect to, e.g., electron cyclotron emission (ECE), are that the measurement is not affected by wall reflections and that the absorption coefficient is nearly independent of the perpendicular energy of the fast electrons. On the other hand, the measurement is affected by refraction effects, which can be calculated by means of a ray-tracing code and/or measured during similar ohmic plasmas in both cases, measurements at a frequency where there is no absorption (fmax>fc), are used as a reference. Parallel tail distributions measured by this method are presented and their relaxation properties are discussed

  3. Electron cyclotron absorption measurements in Tore Supra during lower hybrid current drive

    International Nuclear Information System (INIS)

    A transmission diagnostic system working in the frequency range 77-109 GHz has been implemented in the Tore Supra tokamak. It makes use of an ordinary mode launched along a vertical diameter, i.e., propagating along a nearly constant magnetic field. A modulation of the incident power allows to increase the signal to noise ratio. The purpose of the diagnostic is to measure electron cyclotron absorption (ECA) below the electron cyclotron frequency fc in the presence of the fast electron tails created during lower-hybrid current drive. As is known, for a parallel electron tail, the absorption coefficient at fc is proportional to the parallel distribution function and a frequency scan yields, in principle, the shape of the parallel distribution as a function of the parallel momentum. The main advantages of ECA with respect to, e.g., electron cyclotron emission (ECE), are that the measurement is not affected by wall reflections and that the absorption coefficient is nearly independent of the perpendicular energy of the fast electrons. On the other hand, the measurement is affected by refraction effects, which can be calculated by means of a ray-tracing code and/or measured during similar ohmic plasmas. In both cases, measurements at a frequency where there is no absorption (fmax>fc), are used as a reference. Parallel tail distributions measured by this method are presented and their relaxation properties are discussed. (orig.)

  4. Standard series of direct-current motors for regulated electric drives

    Science.gov (United States)

    Cholewicki, I.; Lubina, M.; Kozhevnikov, V. A.; Kochnev, A. V.; Skoda, K.; Voleskiy, E.

    1984-11-01

    A standard series of d.c. motors for electric drives with speed and torque regulation has been developed. Thyristor-type converters for machine tools with digital program control are also being developed. Meeting future goals requires modification of the motor frame from the conventional round to a nearly square one, a larger ratio of armature stack length to diameter, better cooling, and insulation of a higher temperature class. In addition, it is necessary to laminate the housing partially or completely and to include a compensating winding. The basic motor configuration is 1 M 1001, according to Council of Mutual Economic Assistance (CEMA) Standard 246-78, with at least IP 23S protection and 1C 06 or 1C 05 cooling (shaft height from 112 mm up) and 1C 01 cooling (Shaft height or up to 250 mm). The series will be designed for a reference speed of 1500 rpm with not more than 15% armature current fluctuation, with speeds of 300-3000 rpm depending on voltage and motor size and torque regulation 1:200 (externally cooled motors) or 1;5, 1:10, 1:30 (self-cooled motors). Prototype motors with 132 mm and 355 mm shaft heights have already passed all tests.

  5. Advances in lower hybrid current drive for tokamak long pulse operation. Technology and physics

    International Nuclear Information System (INIS)

    The paper gives a picture of the present status and understanding of technology and physics of Lower Hybrid Current Drive for long pulse operation in tokamaks, including the development of continuous wave (CW) high power klystrons, and its evolutions towards ITER. 3.7 GH / 700 kW CW klystrons produced in series by Thales Electron Devices are now in operation on Tore Supra. First series of eight klystrons delivered more than 4 MW to sustain non-inductive plasmas during 50 s. Moreover, a prototype of 500 kW CW klystron operating at 5 GHz developed for KSTAR by Toshiba Electron Tubes and Devices, and foreseen for ITER, is able to produce RF output powers of 300 kW / 800 s and 450 kW / 20 s on matched load. The situation on wave coupling and antennas is reported, with the latest Tore Supra results of the new CW Passive-Active Multi-junction (PAM) launcher: the antenna concept foreseen for ITER. First experiments with the PAM antenna in Tore Supra have provided extremely encouraging results in terms of power handling and coupling. Relevant ITER power density of ∼25 MW/m2 (2.7 MW of power injected into the plasma) has been maintained over ∼80 s. In addition, LH power of 2.7 MW has been coupled at a plasma-antenna distance of 10 cm. (author)

  6. A survey of electron Bernstein wave heating and current drive potential for spherical tokamaks

    CERN Document Server

    Urban, Jakub; Peysson, Yves; Preinhaelter, Josef; Shevchenko, Vladimir; Taylor, Gary; Vahala, Linda; Vahala, George

    2011-01-01

    The electron Bernstein wave (EBW) is typically the only wave in the electron cyclotron (EC) range that can be applied in spherical tokamaks for heating and current drive (H&CD). Spherical tokamaks (STs), which feature relatively high neutron flux and good economy, operate generally in high-beta regimes, in which the usual EC O- and X- modes are cut-off. In this case, EBWs seem to be the only option that can provide features similar to the EC waves---controllable localized H&CD that can be utilized for core plasma heating as well as for accurate plasma stabilization. The EBW is a quasi-electrostatic wave that can be excited by mode conversion from a suitably launched O- or X-mode; its propagation further inside the plasma is strongly influenced by the plasma parameters. These rather awkward properties make its application somewhat more difficult. In this paper we perform an extensive numerical study of EBW H&CD performance in four typical ST plasmas (NSTX L- and H-mode, MAST Upgrade, NHTX). Coupled...

  7. Augmentation of beam currents in the JAERI tandem-booster accelerator facility

    Energy Technology Data Exchange (ETDEWEB)

    Takeuchi, Suehiro; Matsuda, Makoto; Yoshida, Tadashi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2001-02-01

    Modifications have been executed in these years of the accelerator system, aiming at higher beam currents. Advanced experiments e.g. search of unknown heavy nuclei and their synthesis, need large current accelerators. The use of stripper foils in tandem accelerators for the electron detachment severely limits the beam current, however. The first modification is to install ECR (electron cyclotron resonance) ion source in a high voltage terminal board, multicharged, rare gas ions being accelerated directly. The second is to eliminate the use of the second foils, but to increase the beam intensity. (M. Tanaka)

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2015-11-01

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

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

    CERN Document Server

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

    2015-01-01

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

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

    International Nuclear Information System (INIS)

    In a laser ion source, plasma drift distance is one of the most important design parameters. Ion current density and beam pulse width are defined by plasma drift distance between a laser target and beam extraction position. In direct plasma injection scheme, which uses a laser ion source and a radio frequency quadrupole linac, we can apply relatively higher electric field at beam extraction due to the unique shape of a positively biased electrode. However, when we aim at very high current acceleration such as several tens of milliamperes, we observed mismatched beam extraction conditions. We tested three different ion current at ion extraction region by changing plasma drift distance to study better extraction condition. In this experiment, C6+ beam was accelerated. We confirmed that matching condition can be improved by controlling plasma drift distance.

  12. Full-wave modeling of high harmonic heating and current drive in NSTX

    International Nuclear Information System (INIS)

    The proposed low aspect ratio tokamak experiment, NSTX, provides a totally new and unique environment for ion cyclotron range of frequencies heating and current drive experiments. At the proposed frequency of 41 MHz and magnetic field of 0.3 T, electron beta is high and Landau damping is very strong. Wave energy is rapidly and totally damped between the antenna and plasma center, and the result is a current driven well off axis. High cyclotron harmonic ion resonances also occur in the machine with a ratio of rf frequency to ion cyclotron frequency of 6.0 and above for majority deuterium and 3.0 and above for minority hydrogen. Near the plasma center, the product of perpendicular wave number and ion gyroradius is about 6 for deuterium so that the small Larmor radius expansion clearly breaks down. To calculate ion absorption, it is therefore necessary to use the full modified Bessel functions which are valid for all Larmor radii. We have extended the PICES global wave code to use the modified Bessel functions in evaluating power absorption at the high harmonic ion cyclotron resonances. Results show an ion power fraction of about 0.35 percent at 41 MHz and 3.5 percent at 21 MHz. The question remains as to the validity of the second order Lamor radius expansion is valid. Since the overall wave propagation and absorption is relatively insensitive to ion temperature, it might be argued that the expansion has little effect on the result. However, this conclusion must await more detailed calculations which do not rely on the expansion

  13. Quasi-linear modeling of lower hybrid current drive in ITER and DEMO

    Energy Technology Data Exchange (ETDEWEB)

    Cardinali, A., E-mail: alessandro.cardinali@enea.it; Cesario, R.; Panaccione, L.; Santini, F.; Amicucci, L.; Castaldo, C.; Ceccuzzi, S.; Mirizzi, F.; Tuccillo, A. A. [ENEA, Unità Tecnica Fusione, Via E Fermi 45 Rome (Italy)

    2015-12-10

    First pass absorption of the Lower Hybrid waves in thermonuclear devices like ITER and DEMO is modeled by coupling the ray tracing equations with the quasi-linear evolution of the electron distribution function in 2D velocity space. As usually assumed, the Lower Hybrid Current Drive is not effective in a plasma of a tokamak fusion reactor, owing to the accessibility condition which, depending on the density, restricts the parallel wavenumber to values greater than n{sub ∥crit} and, at the same time, to the high electron temperature that would enhance the wave absorption and then restricts the RF power deposition to the very periphery of the plasma column (near the separatrix). In this work, by extensively using the “ray{sup star}” code, a parametric study of the propagation and absorption of the LH wave as function of the coupled wave spectrum (as its width, and peak value), has been performed very accurately. Such a careful investigation aims at controlling the power deposition layer possibly in the external half radius of the plasma, thus providing a valuable aid to the solution of how to control the plasma current profile in a toroidal magnetic configuration, and how to help the suppression of MHD mode that can develop in the outer part of the plasma. This analysis is useful not only for exploring the possibility of profile control of a pulsed operation reactor as well as the tearing mode stabilization, but also in order to reconsider the feasibility of steady state regime for DEMO.

  14. Amplification of relativistic electron beam current propagating in ambient neutral gases

    International Nuclear Information System (INIS)

    It is experimentally observed that the net current is more than the primary beam current when the relativistic electron beam (REB) is propagated in ambient neutral gases (H2, He, air) at subtorr pressures (0.1-0.3 torr). Chambers attempted to explain the current amplification via the two-stream instability under the assumption of an ultrarelativistic, one-dimensional cold beam, limiting its applicability to specific situations. The authors have derived the current gain (G) expression in general for a scattered REB propagating in a neutral gas by taking into account a quasi-hydrodynamic expression for the beam energy loss. Moreover, the beam-to-plasma density ratio nb/nrho as a function of time is obtained for a given beam pulse by solving the electron energy and continuity equations numerically. It is found that at a given nb/nrho the current gain increases with increasing the beam energy, increases being rapid for the small average scattering angles. A finite average scattering angle is seen to reduce the current amplification

  15. Influence of total beam current on HRTEM image resolution in differentially pumped ETEM with nitrogen gas

    International Nuclear Information System (INIS)

    Environmental transmission electron microscopy (ETEM) enables the study of catalytic and other reaction processes as they occur with Angstrom-level resolution. The microscope used is a dedicated ETEM (Titan ETEM, FEI Company) with a differential pumping vacuum system and apertures, allowing aberration corrected high-resolution transmission electron microscopy (HRTEM) imaging to be performed with gas pressures up to 20 mbar in the sample area and with significant advantages over membrane-type E-cell holders. The effect on image resolution of varying the nitrogen gas pressure, electron beam current density and total beam current were measured using information limit (Young's fringes) on a standard cross grating sample and from silicon crystal lattice imaging. As expected, increasing gas pressure causes a decrease in HRTEM image resolution. However, the total electron beam current also causes big changes in the image resolution (lower beam current giving better resolution), whereas varying the beam current density has almost no effect on resolution, a result that has not been reported previously. This behavior is seen even with zero-loss filtered imaging, which we believe shows that the drop in resolution is caused by elastic scattering at gas ions created by the incident electron beam. Suitable conditions for acquiring high resolution images in a gas environment are discussed. Lattice images at nitrogen pressures up to 16 mbar are shown, with 0.12 nm information transfer at 4 mbar. -- Highlights: ► ETEM images with point resolution of 0.12 nm in 4 mbar of nitrogen gas. ► Clear Si lattice imaging with 16 mbar of nitrogen gas. ► ETEM image resolution in gas can be much improved by decreasing total beam current. ► Beam current density (beam convergence) has no effect on the image resolution.

  16. Design, construction, and electrical test results of dual phase controlled multi-megawatt oscillators for ''oscillating field current drive'' on ZT40M

    International Nuclear Information System (INIS)

    This paper provides the design and construction details and the electrical test results of 1 kHz, 10 MW and 20 MW phase controlled class D or E driven oscillators. To test the concept of oscillating field current drive, the 10 MW oscillator is directly coupled to the toroidal field (TF) circuits; the 20 MW oscillator to the poloidal field (PF) circuits. By maintaining the proper phase angle between PF and TF oscillators, theory shows that for reversed field pinch plasmas, discharges can be sustained without expenditure of mean magnetizing (or drive) flux. Each oscillator consists of an L-C tank circuit driven by 20 parallel ML8618 magnetically beamed triodes. Each circuit can provide up to 45 MVAR of tank circulating power when driven at its maximum rating. For the 10 MW and 20 MW load power requirements, 450 kJ, 22 kV B + capacitor banks will provide for over a 10 mS oscillating envelope. To control phase and amplitude, the grid drive waveform timing and conduction angle of the output tubes are changed. Each driver circuit consists of a fiber optic controlled hot deck with 2 ML8618s in a cathode follower configuration

  17. On the effect of the inductive self-acceleration of heavy-current electron beam

    International Nuclear Information System (INIS)

    The possibility of existing the effect of the electron beam inductive self-acceleration by its reset on the thick diaphragm with a small opening is studied. The computer modeling of the dynamics of the heavy-current relativistic electron beam reset on the thick diaphragm with openings is carried out. The modeled structure constitutes the heavy-current vacuum electron diode with and annular cathode and thick diaphragm with a thin annular opening. The results on modeling the 3 mm opening width, 8 mm diaphragm thickness and 5 kA beam current are presented. The computer modeling results prove the possibility of existence of the effect of the heavy-current electron beam inductive self-acceleration by its transmission through the thick diaphragm with an opening

  18. Coherent electron beam density modulator for driving X-ray free electron lasers

    International Nuclear Information System (INIS)

    We propose a new compact scheme for a Free Electron Laser with more coherent properties for the X-ray beam. Higher FEL performance would be achieved using a train of electron bunches initially accelerated in a linear accelerator. Similar to the RF klystron concept, we propose developing an X-ray FEL which consists of two parts: an X-ray self-seeding electron beam density modulator and an output set of undulators. A density modulator consists of a low-Q X-ray cavity and an undulator, which is placed between the cavity mirrors. We use this undulator as a very high gain amplifier, which compensates the amplitude loss due to monochromatic X-ray reflections from the mirrors. Following the X-ray cavity, the density modulated electron beam is separated from the X-ray beam and then enters the output set of undulators. The frequency spectrum of the final X-ray beam is determined mainly by the bandwidth of the reflected elements in the X-ray cavity

  19. Coherent electron beam density modulator for driving X-ray free electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Novokhatski, A., E-mail: novo@slac.stanford.edu; Decker, F.-J.; Hettel, B.; Nosochkov, Yu.; Sullivan, M.

    2015-02-21

    We propose a new compact scheme for a Free Electron Laser with more coherent properties for the X-ray beam. Higher FEL performance would be achieved using a train of electron bunches initially accelerated in a linear accelerator. Similar to the RF klystron concept, we propose developing an X-ray FEL which consists of two parts: an X-ray self-seeding electron beam density modulator and an output set of undulators. A density modulator consists of a low-Q X-ray cavity and an undulator, which is placed between the cavity mirrors. We use this undulator as a very high gain amplifier, which compensates the amplitude loss due to monochromatic X-ray reflections from the mirrors. Following the X-ray cavity, the density modulated electron beam is separated from the X-ray beam and then enters the output set of undulators. The frequency spectrum of the final X-ray beam is determined mainly by the bandwidth of the reflected elements in the X-ray cavity.

  20. Simulation of Electron Beam Dynamics in a Nonmagnetized High-Current Vacuum Diode

    CERN Document Server

    Anishchenko, Sergey

    2016-01-01

    The electron beam dynamics in a nonmagnetized high-current vacuum diode is analyzed for different cathode-anode gap geometries. The conditions enabling to achieve the minimal {initial} momentum spread in the electron beam are found out. A drastic rise of current density in a vacuum diode with a ring-type cathode is described. The effect is shown to be caused by electrostatic repulsion.

  1. Electron heating, time evolution of bremsstrahlung and ion beam current in electron cyclotron resonance ion sources

    OpenAIRE

    Ropponen, Tommi

    2010-01-01

    This thesis is a study of Electron Cyclotron Resonance Ion Source (ECRIS) plasmas and their properties. The focus has been on time evolution studies of bremsstrahlung emission, ion beam current production and numerical studies of electron heating in ECRIS plasmas. The time scales for reaching steady state bremsstrahlung production at electron energies greater than 30 keV is shown to be on the order of several hundreds of milliseconds. The ion beam currents of different elements...

  2. Drive current of accumulation-mode p-channel SOI-based wrap-gated Fin-FETs

    International Nuclear Information System (INIS)

    Comparisons are performed to study the drive current of accumulation-mode (AM) p-channel wrap-gated Fin-FETs. The drive current of the AM p-channel FET is 15%-26% larger than that of the inversion-mode (IM) p-channel FET with the same wrap-gated fin channel, because of the body current component in the AM FET, which becomes less dominative as the gate overdrive becomes larger. The drive currents of the AM p-channel wrap-gated Fin-FETs are 50% larger than those of the AM p-channel planar FETs, which arises from effective conducting surface broadening and volume accumulation in the AM wrap-gated Fin-FETs. The effective conducting surface broadening is due to wrap-gate-induced multi-surface conduction, while the volume accumulation, namely the majority carrier concentration anywhere in the fin cross section exceeding the fin doping density, is due to the coupling of electric fields from different parts of the wrap gate. Moreover, for AM p-channel wrap-gated Fin-FETs, the current in channel along (110) is larger than that in channel along (100), which arises from the surface mobility difference due to different transport directions and surface orientations. That is more obvious as the gate overdrive becomes larger, when the surface current component plays a more dominative role in the total current. (semiconductor devices)

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

    Science.gov (United States)

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

    2011-04-01

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

  4. First Experimental Results with the ITER-Relevant Lower Hybrid Current Drive Launcher in Tore Supra

    International Nuclear Information System (INIS)

    Full text: The new ITER-relevant Lower Hybrid Current Drive (LHCD) launcher, based on the Passive Active Multi-junction (PAM) concept, was brought into operation on the Tore Supra tokamak in October 2009. The PAM launcher concept was designed in view of ITER to allow efficient cooling of the waveguides due to plasma radiation, RF losses and neutron damping. In addition, it offers low power reflection close to the cut-off density, which is important in view of ITER, where the large distance between the plasma and the wall may bring the density in front of the launcher to low values. The complete system operated successfully on Tore Supra already on the second experimental day, coupling 0.4 MW into the plasma for 4.5 s. The maximum power and energy reached so far, after ∼ 400 pulses on plasma, is 2.7 MW during 77 s (exceeding 200 MJ injected energy). This corresponds to a power density of 25 MW/m2 , i.e. its design value at f =3.7 GHz. The main goals of the initial experimental campaign were to: i) compare the coupling behaviour of the PAM launcher to the predictions from the ALOHA code, ii) demonstrate reliable power handling during edge perturbations mimicking ELMs and iii) achieve ITER-relevant power densities in pulse lengths exceeding several seconds. The power reflection coefficient (RC) behaviour on the PAM launcher shows good agreement with calculations, carried out with the ALOHA code. The average RC is 2. In addition, 2.7 MW was coupled at a plasma-launcher distance of 10 cm. The launcher front face security, based on infrared imaging and CuXIX-line emission, showed no arcing at the PAM launcher mouth during high LHCD power. (author)

  5. High RF power test of a CFC antenna module for lower hybrid current drive

    International Nuclear Information System (INIS)

    A mock-up of a 3.7 GHz Lower Hybrid Current Drive (LHCD) antenna module was fabricated from Carbon Fibre Composite (CFC) for the development of heat resistive low Z front facing the plasma. This 2 divided waveguide module is made from CFC plates and rods which are Cu-plated to reduce the RF losses. The withstand-voltage, the RF properties and the outgassing rates for long pulses and high RF power were tested at the Lower Hybrid test bed facility of Cadarache. A reference module made from Dispersion Strengthened Copper (DSC) was also fabricated. After the short pulse conditioning, long pulses with a power density ranging between 50 and 150 MW/m2 were performed with no breakdowns on the CFC module. It was also checked that the highest power density, up to 150 MW/m2, could be transmitted when the waveguides are filled with H2 at a pressure of 5 x 10-2 Pa. During a long pulse, the power reflection coefficient remains low in the 0.8-1.3 % range and no significant change in the reflection coefficient is measured after the thermal cycling provided by the long pulse operation. From thermocouple measurements, RF losses of the copper coated CFC and the DSC modules were compared. No significant differences were measured. From pressure measurements, it was found that the outgassing rate of Cu-plated CFC is about 6-7 times larger than of DSC at 300 deg.C. It is concluded that a CFC module is an attractive candidate for the hardening of the tip of the LHCD antenna. (author)

  6. Real-Time Control, Acquisition and Data Treatment for Beam Current Transformers in a Transfer Line

    CERN Document Server

    Carter, C; Gelato, G; Lenardon, F; Ludwig, M; Schnell, J D

    1997-01-01

    Particle beams are transferred from the 1 GeV Booster to the 26 GeV Proton Synchrotron and to an experimental area, ISOLDE. The characteristics of the beams and their destination change on a 1.2 s cycle basis. There are six beam current transformers to measure the beam intensities, i.e. the number of particles passing through the transfer lines. On each pulse of the Booster, a real-time system, called BTTR (Beam Transfer TRansformers), acquires the transformer values, selects the range, executes a calibration, and treats the data. Part of the treatment is the subtraction of the base-value, which includes systematic perturbations, acquired in the absence of beam. The system also handles asynchronous tasks, such as acquisition of base-value, readout of calibration factors and other diagnostic actions. The concept of the BTTR and its design are presented, as well as some practical results.

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Spethmann, A., E-mail: spethmann@physik.uni-kiel.de; Trottenberg, T., E-mail: trottenberg@physik.uni-kiel.de; Kersten, H., E-mail: kersten@physik.uni-kiel.de [Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel (Germany)

    2015-01-15

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

  9. Characterization of Charging Control of a Single Wafer High Current Spot Beam Implanter

    International Nuclear Information System (INIS)

    This paper focuses on the characterization of charging control of an Axcelis Optima HD single wafer high current spot beam implanter using MOS capacitors with attached antennas of different size and shape. Resist patterns are implemented on Infineon Technologies own charging control wafers to investigate the influence of photo resist on charging damage. Compared to batch high current implanters the design of the beamline and the beam shape are comparable to single wafer high current spot beam implanters, however due to the different scanning architecture the dose rate of the single wafer high current spot beam implanters is significantly higher compared to the batch tools. Therefore, the risk of charging damage will be higher. The charging damage was studied as a function of the energy, the beam current and the most important plasma flood gun parameters. The results have shown that for very high antenna ratios the charging damage for single wafer implanters, even spot or ribbon beam implanters, is higher than for high current batch implanters.

  10. High current relativistic beam propagates stably in gas surrounded by nonconducting walls

    International Nuclear Information System (INIS)

    LLL has been studying the propagation of high current electron beams for a number of years to understand their behavior for use in a variety of experimental uses. Our latest experiments have shown that a mildly relativistic electron beam of 10 to 15 kA and a pulse width of 30 to 40 ns can propagate stably and with no net current transfer in insulating tubes filled with neutral gases. These experiments have been performed in the Magnetic Fusion Energy program where Electronics Engineering has been operating an electron beam accelerator, designing some of the diagnostics, such as laser interferometers, and performing the experiments. This article briefly describes our experimental observations

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

    Energy Technology Data Exchange (ETDEWEB)

    Padilla, M.J.; Blokland, W.

    2009-01-01

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

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

    International Nuclear Information System (INIS)

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

  13. Wideband Precision Current Transformer for the Magnet Current of the Beam Extraction Kicker Magnet of the Large Hadron Collider

    CERN Document Server

    Gräwer, G

    2004-01-01

    The LHC beam extraction system is composed of 15 fast kicker magnets per beam to extract the particles in one turn of the collider and to safely dispose them on external absorbers. Each magnet is powered by a separate pulse generator. The generator produces a magnet current pulse with 3 us rise time, 20 kA amplitude and 1.8 ms fall time, of which 90 us are needed to dump the beam. The beam extraction system requires a high level of reliability. To detect any change in the magnet current characteristics, which might indicate a slow degradation of the pulse generator, a high precision wideband current transformer will be installed. For redundancy reasons, the results obtained with this device will be cross-checked with a Rogowski coil, installed adjacent to the transformer. A prototype transformer has been successfully tested at nominal current levels and showed satisfactory results compared with the output of a high frequency resistive coaxial shunt. The annular core of the ring type transformer is composed of...

  14. Exploring the energy/beam current parameter space for the isotope production facility (IPF) at LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Gulley, Mark S [Los Alamos National Laboratory; Bach, Hong [Los Alamos National Laboratory; Nortier, Francis M [Los Alamos National Laboratory; Pillai, Chandra [Los Alamos National Laboratory; Bitteker, Leo J [Los Alamos National Laboratory; John, Kevin D [Los Alamos National Laboratory; Valdez, Frank O [Los Alamos National Laboratory; Seifter, Achim [Los Alamos National Laboratory

    2010-09-07

    IPF has recently investigated isotope production with proton beams at energies other than the 100-MeV currently available to the IPF beam line. To maximize the yield of a particular isotope, it is necessary to measure the production rate and cross section versus proton beam energy. Studies were conducted at 800 MeV and 197 MeV to determine the cross section of Tb-159. Also, the ability to irradiate targets at different proton beam energies opens up the possibility of producing other radioisotopes. A proof-of-principle test was conducted to develop a 40-MeV tune in the 100-MeV beam line. Another parameter explored was the beam current, which was raised from the normal limit of 250 {mu}A up to 356 {mu}A via both power and repetition rate increase. This proof-of-principle test demonstrated the capability of the IPF beam line for high current operation with potential for higher isotope yields. For the full production mode, system upgrades will need to be in place to operate at high current and high duty factor. These activities are expected to provide the data needed for the development of a new and unique isotope production capability complementing the existing 100-MeV IPF facility.

  15. A nonlinear magnetic helicity model of a tight aspect ratio bootstrapped tokamak with oscillating field current drive

    International Nuclear Information System (INIS)

    Theoretical and computational analyses of bootstrapped tokamaks with oscillating field current drive (OFCD) have been developed using a nonlinear magnetic helicity model. Assuming a rigid current profile, the conditions for optimal tokamak steady-state operation are derived and are shown to agree with the results of computer calculations. Generalized limit formulae for the toroidal plasma beta and bootstrap current fraction are also obtained. The results of the analyses indicate that steady-state bootstrapped tokamak operation with high toroidal plasma beta can best be achieved in tight aspect ratio A → 1 reactors with OFCD supplying as much as a quarter of the total toroidal plasma current. (author)

  16. Vertical comb drive microscanners for beam steering, linear scanning, and laser projection applications

    OpenAIRE

    Jung D.; Sandner T.; Kallweit D.; Schenk H.

    2012-01-01

    This paper describes in detail our concept of quasi-static micro scanning mirrors enabling large static deflections and linearized scanning using vertical out-of-plane comb drives. The vertical comb configuration is realized from a planar scanner substrate by wafer bonding. The device concept is highly flexible by design; different kinds of vertical combs (e.g. staggered and angular) can be realized without changing the technological process flow but by design modifications, only. First demon...

  17. Four Pulse Drive System for the Beam Induction Cells and Injector for DARHT Axis 2

    International Nuclear Information System (INIS)

    The proposed drive system allows for the generation of up to four (4) high-quality radiographic pulses along one line-of-sight, having arbitrary pulse spacing (approximately500 ns), using demonstrated technologies. This concept uses a four-pulse drive system to drive both a 16-MeV ensemble of 250-kV, 4-kA induction cells and a four-pulse, 4-MeV injector. The key to this approach lies in the method used to combine four pulses from different generators in a manner that does not compromise the voltage flatness requirement of ± 1%. The induction cells use core material for only a single pulse. A simple reverse bias circuit is used to reset the cores between pulses, and the insulator has been redesigned to withstand the reverse reset voltage. This approach can be installed in stages so that the facility can be used for dual axis radiography while implementing the multi-pulsing capability. A dual double-pulse format has been identified which provides a sequence of two pulses along one line-of-sight within a 2-microsec window. The 2-microsec windows can be separated by arbitrary time intervals of 2- to 10-microsec

  18. Current density profile and electron beam localization measurements using carbon pellets on T-10

    International Nuclear Information System (INIS)

    The letter presents experimental evidence and an analysis of two phenomena arising during carbon pellet ablation - a toroidal trajectory deflection and enhanced localized ablation in the electron cyclotron resonance (ECR) current drive regime. A model developed for describing the toroidal deflection of a carbon pellet in a tokamak shows that the trajectory curvature is sensitive to the current density. Photography of the pellet trajectory is used as a diagnostic for the determination of the local current density in an ohmically heated plasma. Directly measured current profiles using pellets are in reasonable agreement with that obtained using the Spitzer conductivity, and current density fluctuations have been observed that are probably associated with magnetic islands. It is shown that in the ECR current drive regime on T-10, energetic electrons probably stimulated by the microwave power are located in a narrow zone (2 cm thickness in the radial direction) with sharp boundaries. (author). Letter-to-the-editor. 7 refs, 5 figs

  19. LETTER: Current density profile and electron beam localization measurements using carbon pellets on T-10

    Science.gov (United States)

    Egorov, S. M.; Kuteev, B. V.; Miroshnikov, I. V.; Mikhailenko, A. A.; Sergeev, V. Yu.; Ushakov, S. N.; Bagdasarov, A. A.; Chistyakov, V. V.; Elizavetin, D. Yu.; Vasin, N. L.

    1992-11-01

    The authors present experimental evidence and an analysis of two phenomena arising during carbon pellet ablation-a toroidal trajectory deflection and enhanced localized ablation in the electron cyclotron resonance (ECR) current drive regime. A model developed for describing the toroidal deflection of a carbon pellet in a tokamak shows that the trajectory curvature is sensitive to the current density. Photography of the pellet trajectory is used as a diagnostic for the determination of the local current density in an ohmically heated plasma. Directly measured current profiles using pellets are in reasonable agreement with that obtained using the Spitzer conductivity, and current density fluctuations have been observed that are probably associated with magnetic islands. It is shown that in the ECR current drive regime on T-10, energetic electrons probably stimulated by the microwave power are located in a narrow zone (2 cm thickness in the radial direction) with sharp boundaries

  20. Nonthermal particle and full-wave diffraction effects on heating and current drive in the ICRF and LHRF regimes

    International Nuclear Information System (INIS)

    Fast waves (FW) are a primary technique for heating and current drive (CD) on the proposed burning plasma device, ITER, and lower hybrid (LH) waves are a candidate for edge current profile control. The models used to simulate these two waves rely on assumptions of Maxwellian populations that allow efficient analytic implementations of the plasma response, and in the case of the LH wave, the ray tracing models used are able to follow the very small wavelengths in a continuum manner without requiring a fine computational grid. Recent advances in algorithms and parallel computational methods have allowed these assumptions to be tested, permitting more accurate estimates of heating deposition and CD efficiencies in a burning plasma. Absorption by energetic particles for both waves can be significant, reducing electron heating and associated CD. Wave propagation and absorption is dependent on the velocity space distribution of particles in the plasma and on the geometric effects of focusing and diffraction. Fusion born alpha particles and neutral beam ions may interact with these waves in a manner that cannot be accurately modeled by Maxwellian distributions. The AORSA2D code has been modified to use a generalized non-Maxwellian conductivity, and has been applied to ITER reference scenarios. Preliminary analysis for ITER suggests that alpha absorption may be limited to a few tens of percent, and thus, allow reasonable CD efficiencies, assuming that the RF does not significantly alter the alpha slowing-down distribution. We also discuss the interaction of an energetic Tritium tail with FW in ITER. In addition, the effects of diffraction on LH waves in toroidal geometry are not well understood because computational limits have prohibited full-wave simulations at those small wavelengths. Simulations of LH waves have been restricted to WKB ray tracing techniques and 1D full-wave in the past, but the availability of massively parallel architectures have made full

  1. INCREASED STABLE BETA IN DIII-D BY SUPPRESSION OF A NEOCLASSICAL TEARING MODE USING ELECTRON CYCLOTRON CURRENT DRIVE AND ACTIVE FEEDBACK

    International Nuclear Information System (INIS)

    OAK A271 INCREASED STABLE BETA IN DIII-D BY SUPPRESSION OF A NEOCLASSICAL TEARING MODE USING ELECTRON CYCLOTRON CURRENT DRIVE AND ACTIVE FEEDBACK. In DIII-D, the first real-time active control of the electron cyclotron current drive stabilization of a neoclassical tearing mode (here m/n=3/2) is demonstrated. The plasma control system is put into a search and suppress mode to align the ECCD with the island by making either small rigid radial position shifts (of order 1 cm) of the entire plasma (and thus the island) or small changes in toroidal field (of order 0.5%) which radially moves the second harmonic resonance location (and thus the rf current drive). The optimum position minimizes the real-time mode amplitude signal and stabilization occurs despite changes in island location from discharge-to-discharge or from time-to-time. When the neutral beam heating power is programmed to rise after mode suppression by the ECCD, the plasma pressure increases above the peak at the onset of the neoclassical tearing mode until the magnetic island reappears due to the ECCD no longer being on the optimal position. Real-time tracking of the change in location of q=3/2 due to the Shafranov shift with increasing beta is necessary to position the ECCD in the absence of a mode so that higher stable beta can be sustained. The control techniques developed for the m/n=3/2 NTM are also being applied to the more deleterious m/n-2/1 NTM. For the first time in any tokamak, an m/n=2/1 mode has been completely suppressed using radially localized off-axis ECCD

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

    Science.gov (United States)

    Agafonov, A. V.

    2006-12-01

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

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

    International Nuclear Information System (INIS)

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

  4. Impact of Electric Current Fluctuations Arising from Power Supplies on Charged-Particle Beams

    CERN Document Server

    Yoon, P S

    2008-01-01

    Electric current fluctuations are one type of unavoidable machine imperfections,and induce magnetic-field perturbations as a source of instabilities in accelerators. This paper presents measurement-based methodology of modeling the fluctuating electric current arising from the power system of Fermilab's Booster synchrotron to discuss the ramifications of the presence of ripple current and space-charge defocusing effects. We also present the method of generating stochastic noise and the measurement and analysis methods of ripple current and offending electromagnetic interferences residing in the Booster power system. This stochastic noise model, accompanied by a suite of beam diagnostic calculations, manifests that the fluctuating power-supply current, when coupled to space charge and impinging upon a beam, can substantially enhance beam degradation phenomena--such as emittance growth and halo formation--during the Booster injection period. With idealized and uniform charge-density distribution, fractional gro...

  5. Design and development of low current measurement electronics for beam diagnostics system

    International Nuclear Information System (INIS)

    Beam diagnostics devices are essential constituents of any particle accelerator. In many beam diagnostics devices such as wire beam profile monitor (wire-BPM), Faraday cup etc., low current signal processing and measurement is carried out. In this paper low current measurement using a trans-impedance amplifier, based on T-network topology of feedback resistors is presented. This technique employs a T-network of relatively lower value resistors in the feedback path of op-amp to achieve high gain without requiring high value resistors which have associated leakage problems. The designed low current signal processing electronics based on this technique can linearly measure current signal in the rage of 100pA to 1μA, To accommodate wide range of current measurement, four selectable gains of trans-impedance amplifier have been incorporated in the circuit. The microcontroller based processing electronics monitors the real time low current signal, then automatically switches the appropriate gain to match the input current for its accurate measurement. It has been tested and calibrated successfully in lab with standard low current source. The processing electronics has also been tested and verified for current signal measurement of a wire-BPM installed at the visible diagnostic beam line (BL-24) of Indus-2, synchrotron light source at RRCAT, Indore. (author)

  6. High Current Beam Dynamics in an Ess SC Linac

    CERN Document Server

    Pabst, M; Letchford, A P

    2000-01-01

    Three alternative designs of the European Spallation Source (ESS) high energy linac are described. The most promising ones are either a normalconducting (nc) coupled cavity linac (CCL) up tofinal energy or a change at 407 MeV to only one group of 6 cell superconducting (sc) elliptical cavities. Fully 3d Monte Carlo simulations are presented for both options, optimized for reduced halo formation at the linac end. For the error free matched case, especially the halo formation in the longitudinal plane is more pronounced for the hybrid solution with its superconducting cavities, caused by the unavoidable phase slippage, but still quite well acceptable for loss free ring injection. Simulations however for a 30% mismatched dense core, surrounded in addition by 1.5% halo particles are showing few particles with very large amplitudes even in real space. This case represents halo formation in front to end simulations, caused by current fluctuations, filamented RFQ output distribution and enhanced by accumulated field...

  7. Design and commissioning of the APS beam charge and current monitor

    International Nuclear Information System (INIS)

    The non-intercepting charge and current monitors suitable for a wide range of beam parameters have been developed and installed in the Advanced Photon Source (APS) low energy transport lines, positron accumulator ring (PAR), and injector synchrotron. The positron or electron beam pulse in the APS has charge ranging from 100pC to l0nC with pulse width varying from 30ps to 30ns. The beam charge and current are measured with a current transformer and subsequent current monitoring electronics based on an ultrafast, high precision gated integrator. The signal processing electronics, data acquisition, and communication with the control system are managed by a VME-based system. This paper summarizes the hardware and software features of the systems. The results of recent operations are presented

  8. Applicability evaluation of eddy current testing for underwater laser beam welding

    International Nuclear Information System (INIS)

    We clarified a defect detecting capability of eddy current testing (ECT) as a surface inspection technique for underwater laser beam welding. An underwater laser beam welding procedure includes groove caving as a preparation, laser beam welding in groove and welding surface grinding as a post treatment. Therefore groove and grinded welding surface inspections are required underwater. We curried out defect detection tests using three kinds of specimens simulated a groove, reactor vessel nozzle dissimilar metal welding materials and a laser beam welding material with a cross coil ECT probe. From experimental results, we confirmed that it is possible to detect 0.3 mm or more depth electro-discharge machining slits on machining surfaces in all specimens and an ECT has possibility as a surface inspection technique for underwater laser beam welding. (author)

  9. Results of Beam Tests on a High Current EBIS Test Stand

    International Nuclear Information System (INIS)

    At Brookhaven National Laboratory there is an R and D program to design an Electron Beam Ion Source (EBIS) for use in a compact ion injector to be developed for the relativistic heavy ion collider (RHIC). The BNL effort is directed at developing an EBIS with intensities of 3 x 109 particles/pulse of ions such as Au35+ and U45+, and requires an electron beam on the order of 10A. The construction of a test stand (EBTS) with the full electron beam power and 1/3 the length of the EBIS for RHIC is nearing completion. Initial commissioning of the EBTS was made with pulsed electron beams of duration < 1 ms and current up to 13 A. Details of the EBTS construction, results of the pulse tests, and preparations for DC electron beam tests are presented

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-06-25

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

  11. Positron source investigation by using CLIC drive beam for Linac-LHC based e+p collider

    Science.gov (United States)

    Arιkan, Ertan; Aksakal, Hüsnü

    2012-08-01

    Three different methods which are alternately conventional, Compton backscattering and Undulator based methods employed for the production of positrons. The positrons to be used for e+p collisions in a Linac-LHC (Large Hadron Collider) based collider have been studied. The number of produced positrons as a function of drive beam energy and optimum target thickness has been determined. Three different targets have been used as a source investigation which are W75-Ir25, W75-Ta25, and W75-Re25 for three methods. Estimated number of the positrons has been performed with FLUKA simulation code. Then, these produced positrons are used for following Adiabatic matching device (AMD) and capture efficiency is determined. Then e+p collider luminosity corresponding to the methods mentioned above have been calculated by CAIN code.

  12. Analysis of Longitudinal Beam Dynamics Behavior and RF System Operative Limits at High Beam Currents in Storage Rings

    Energy Technology Data Exchange (ETDEWEB)

    Mastorides, T; Rivetta, C.; Fox, J.D.; Winkle, D.Van; /SLAC; Tytelman, D.; /Dimtel, Redwood City

    2008-07-07

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

  13. Focusing of heavy ion beams by a high-current plasma lens

    International Nuclear Information System (INIS)

    Results are presented from studies of the focusing of wide-aperture low-energy (100-400 eV) and moderate-energy (5-25 keV) beams of heavy-metal ions by a high-current electrostatic plasma lens. It is found experimentally that, because of the significant electron losses, the efficient focusing of such beams can be achieved only if the external potentials at the plasma-lens electrodes are maintained constant. Static and dynamic characteristics of the lens are studied under these conditions. It is shown that, as the beam current and the electrode voltage increase, the maximum electrostatic field in the lens tends to a certain limiting value because of the increase in the spatial potential near the lens axis. The role of spherical and moment aberrations in the focusing of wide-aperture low-divergence ion beams is revealed. It is shown that, even when spherical aberrations are minimized, unremovable moment aberrations decrease the maximum compression ratio of a low-energy heavy-ion beam because of the charge separation of multiply charged ions in the focal region. At the same time, as the ion energy increases, the role of the moment aberrations decreases and the focusing of high-current heavy-ion beams by a plasma lens becomes more efficient than the focusing of light-ion (hydrogen) beams. This opens up the possibility of using electrostatic plasma lenses to control ion beams in high-dose ion implanters and high-current accelerators of heavy ions

  14. Stable propagation of a high-current electron beam: experimental observations and computational modeling

    International Nuclear Information System (INIS)

    Experimental studies of self-focused, high-current electron-beam propagation phenomena are compared with the results of computational modeling. The model includes the radial structure of the beam-plasma system, a full electromagnetic field description, primary and secondary gas ionization processes, and a linear theory of the hose-like distortions. Good agreement between the experimental results and the computations strengthens the premise that hose instability is the principal limitation to propagation at high pressure

  15. Current status of electron beam treatment of flue gas in China

    International Nuclear Information System (INIS)

    Fossil resource especially coal will remain the main energy resource in China over the next 3 ∼4 decades. Pollution of flue gas from fossil power station is one problem being desiderated to solve since 1990's. Electron beam treatment of flue gas as an advanced technique has been developed and used by some institutes and industries in China. The current status of flue gas treatment using electron beam and the development of electron accelerator in China are reviewed. (author)

  16. Measurements of current density distribution in shaped e-beam writers

    Czech Academy of Sciences Publication Activity Database

    Bok, Jan; Horáček, Miroslav; Kolařík, Vladimír; Urbánek, Michal; Matějka, Milan; Krzyžánek, Vladislav

    2016-01-01

    Roč. 149, JAN 5 (2016), s. 117-124. ISSN 0167-9317 R&D Projects: GA ČR(CZ) GA14-20012S; GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : shaped e-beam writer * electron beam * current density Subject RIV: JB - Sensors, Measurment, Regulation Impact factor: 1.197, year: 2014

  17. CEBAF [Continuous Electron Beam Accelerator Facility] superconducting cavity rf drive system

    International Nuclear Information System (INIS)

    The CEBAF rf system consists of 418 individual rf amplifier chains. Each superconducting cavity is phase locked to the master drive reference line to within 1 degree, and the cavity field gradient is regulated to within 1 part in 104 by a state-of-the-art rf control module. Precision, continuously adjustable, modulo 3600 phase shifters are used to generate the individual phase references, and a compensated rf detector is used for level feedback. The close coupled digital system enhances system accuracy, provides self-calibration, and continuously checks the system for malfunction. Calibration curves, the operating program, and system history are stored in an on board EEPROM. The rf power is generated by a 5kW, water cooled, permanent magnet focused klystron. The klystrons are clustered in groups of 8 and powered from a common supply. rf power is transmitted to the accelerator sections by semiflexible waveguide

  18. Focusing of heavy ion beams by a high-current plasma lens

    International Nuclear Information System (INIS)

    The results of studies on focusing the wide-aperture heavy ion beams by a high-current electrostatic plasma lens within the range of low (100-400 eV) and medium (5-25 keV) energies are presented. It si established, that due to significant electron leakages the effective focusing of such beams is possible only under the condition of rigid fixation of the external potentials on the plasma lens electrodes. The peculiarities of the lens static and dynamic characteristics under such conditions are studied. The role of spherical and moment aberrations by focusing the wide-aperture weakly-diverging ion beams is identified. It is shown, that the role of the moment aberrations decreases with the energy growth, and focusing of the heavy elements high-current beams by the plasma lens becomes considerably more efficient as compared, to the focusing of the hydrogen light ion beams. This opens the possibility for application of electrostatic plasma lenses for controlling the ion beams in the high-dose ion implanters and in the high-current heavy-ion accelerators

  19. High-current pulse sources of broad beams of gas and metal ions for surface treatment

    International Nuclear Information System (INIS)

    This paper reviews the experimental study, development, and improvement of various types of processing ion sources undertaken in association with the joint program performed in recent years by the Institute of Electrophysics and the Institute of High-Current Electronics of the Russian Academy of Sciences. The beam parameters (type and energy of ions, current density, cross-sectional area of the beam, permissible content of impurities, etc.) should meet the requirements of particular ion beam treatment conditions, while the ion source itself should be simple and reliable in operation. Technical and service characteristics of the developed ion sources permit their use for ion-beam modification of materials, preparation of surfaces and ion-assisted deposition of thin films, and in some other applications. The sources under consideration employ high-current glow discharges with a hollow cathode or in crossed electric and magnetic fields, and low-pressure arc discharges and vacuum arc. Cold cathodes enhance reliability of the ion sources when they work at a high residual gas pressure or in the reactive gas media. The repetitive pulse mode of the plasma and beam generation provides optimum conditions for stable operation of the discharge, control of the average beam current over a wide range, and formation of homogeneous large-cross-section beams. The paper describes techniques used to realize high-current discharges at a reduced pressure, methods for producing a stable, dense and homogeneous plasma in a large volume, techniques of formation of large-cross-section homogeneous beams, and also findings on the mass-charge composition of the plasma and beams produced. Some design versions of the sources are given. At voltages from 10 to 100 kV, the pulse duration of 10 to 1000 μs, and the pulse repetition rate of 1 to 500 Hz these sources provide the current density of ∼1-10 mA/cm2 in beams having the cross-sectional area of a few hundreds of square centimeters. The

  20. Application of intense relativistic electron beams to the switching of high currents in high power electrical networks

    International Nuclear Information System (INIS)

    A new concept of switching of high currents using intense relativistic electron beams propagating in vacuum drift tubes is presented. Some possible applications of this concept for the design of current switches are discussed. Supporting analytical one-dimensional theory of an electron beam switch is given. Electron beam hysteresis phenomenon associated with the switching mechanism is briefly discussed

  1. System for tunerless operation of a four-element phased array antenna for fast wave current drive

    International Nuclear Information System (INIS)

    A simple transmission line configuration for powering a four-element phased antenna array is described. This system, called the balanced feed configuration (BFC) is suitable for co- or counter- Fast Wave Current Drive (FWCD) applications. It has the property of presenting a constant matched load to the transmitter despite wide variations in the antenna load impedance without the use of variable tuning elements. This system has been implemented on a 2 MW 60 MHz FWCD antenna on the DIII-D tokamak

  2. Comparison of Current Control Strategies Applied to a Boost-Rectifier Connected to a Direct Drive Wave Energy Converter

    OpenAIRE

    Rocha Mendonca, Hugo; Martínez González, Sergio; Ramírez Prieto, Dionisio

    2015-01-01

    Direct drive wave energy converters are characterized by a direct conversion of the wave energy into electricity with no intermediate mechanical conversion system. For this reason, optimization methods for maximizing the absorbed power have to be designed for acting on the electrical generator. Besides, this type of system requires power electronics to be connected to the grid. This paper evaluates three different current control strategies applied to a boost-rectifier in the ac-dc stage as p...

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2014-03-01

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

  5. Compact ASD Topologies for Single-Phase Integrated Motor Drives with Sinusoidal Input Current

    DEFF Research Database (Denmark)

    Klumpner, Christian; Blaabjerg, Frede; Thoegersen, Paul

    2005-01-01

    A standard configuration of an Adjustable Speed Drive (ASD) consists of two separate units: an AC motor, which runs with fixed speed when it is supplied from a constant frequency grid voltage and a frequency converter, which is used to provide the motor with variable voltage-variable frequency...... needed to adjust the speed of the motor. The integrated motor drive concept is a result of merging the two units in order to achieve the following benefits [1-3]: reducing the design and the commissioning time in complex industrial equipments, no need for a cabinet to host the frequency converter, no...... induction motor as a boost inductor for a PFC (Power Factor Correction) stage controlled by the inverter zero-sequence voltage component. By determining how much energy is possible to store in a corner inductor, it is proven that integrating the magnetics into the stator yoke is a feasible solution...

  6. MODELING AND ANALYSIS OF DISTRIBUTION LOAD CURRENTS PRODUCED BY AN AD JUSTABLE SPEED DRIVE HEAT PUMP

    OpenAIRE

    Hoffman, Stephen Paul

    1993-01-01

    A number of demand side management techniques have been proposed for the efficient use of electric power in the commercial and residential sector. The adjustable speed drive heat pump is a technology which has the prospect of decreasing power demands for space heating. This design has the advantage over conventional designs of higher efficiency and, potentially, reduction of peak power demand. Its main disadvantage is higher cost. Further, it has the disadvantage that it produces a load curre...

  7. Study on Current Sensorless Vector Control Method for Electric Vehicle Drive Motor

    OpenAIRE

    Xiaoyong Shen; Linhui Li; Jing Chang; Yafu Zhou; Jing Lian

    2013-01-01

    With the aggravation of environment pollution and the reduction of petroleum resources, the development of electric vehicle (EV) draws more and more people’s attention. In the EV research field, that seeking for a high efficient and reliable motor control method that suits the operating conditions and characteristics of the vehicle drive motor has become one of the key techniques that need to be broken through urgently. Owing to the problems that the efficient work area is narrow and it leads...

  8. Effects of drive current rise-time and initial load density distribution on Z-pinch characteristics

    Institute of Scientific and Technical Information of China (English)

    Duan Yao-Yong; Guo Yong-Hui; Wang Wen-Sheng; Qiu Ai-Ci

    2005-01-01

    A two-dimensional, three-temperature radiation magneto-hydrodynamics model is applied to the investigation of evolutional trends in x-ray radiation power, energy, peak plasma temperature and density as functions of drive current rise-time and initial load density distribution by using the typical experimental parameters of tungsten wire-array Z-pinch on the Qiangguang-Ⅰ generator. The numerical results show that as the drive current rise-time is shortened, x-ray radiation peak power, energy, peak plasma density and peak ion temperature increase approximately linearly, but among them the x-ray radiation peak power increases more quickly. As the initial plasma density distribution in the radial direction becomes gradually flattened, the peak radiation power and the peak ion-temperature almost exponentially increase, while the radiation energy and the peak plasma density change only a little. The main effect of shortening drive current rise-time is to enhance compression of plasma, and the effect of flattening initial load density distribution in the radial direction is to raise the plasma temperature. Both of the approaches elevate the x-ray peak radiation power.

  9. Development of long pulse RF heating and current drive for H-mode scenarios with metallic walls in WEST

    Energy Technology Data Exchange (ETDEWEB)

    Ekedahl, Annika, E-mail: annika.ekedahl@cea.fr; Bourdelle, Clarisse; Artaud, Jean-François; Bernard, Jean-Michel; Bufferand, Hugo; Colas, Laurent; Decker, Joan; Delpech, Léna; Dumont, Rémi; Goniche, Marc; Helou, Walid; Hillairet, Julien; Lombard, Gilles; Magne, Roland; Mollard, Patrick; Nardon, Eric; Peysson, Yves; Tsitrone, Emmanuelle [CEA, IRFM, F-13108 Saint Paul-lez-Durance (France)

    2015-12-10

    The longstanding expertise of the Tore Supra team in long pulse heating and current drive with radiofrequency (RF) systems will now be exploited in the WEST device (tungsten-W Environment in Steady-state Tokamak) [1]. WEST will allow an integrated long pulse tokamak programme for testing W-divertor components at ITER-relevant heat flux (10-20 MW/m{sup 2}), while treating crucial aspects for ITER-operation, such as avoidance of W-accumulation in long discharges, monitoring and control of heat fluxes on the metallic plasma facing components (PFCs) and coupling of RF waves in H-mode plasmas. Scenario modelling using the METIS-code shows that ITER-relevant heat fluxes are compatible with the sustainment of long pulse H-mode discharges, at high power (up to 15 MW / 30 s at I{sub P} = 0.8 MA) or high fluence (up to 10 MW / 1000 s at I{sub P} = 0.6 MA) [2], all based on RF heating and current drive using Ion Cyclotron Resonance Heating (ICRH) and Lower Hybrid Current Drive (LHCD). This paper gives a description of the ICRH and LHCD systems in WEST, together with the modelling of the power deposition of the RF waves in the WEST-scenarios.

  10. Two-Dimensional Hybrid Model for High-Current Electron Beam Transport in a Dense Plasma

    Institute of Scientific and Technical Information of China (English)

    CAO Lihua; WANG Huan; ZHANG Hua; LIU Zhanjun; WU Junfeng; LI Baiwen

    2014-01-01

    A two-dimensional hybrid code is developed to model the transport of a high-current electron beam in a dense plasma target.The beam electrons are treated as particles and described by particle-in-cell simulation including collisions with the target plasma particles.The background target plasma is assumed to be a stationary fluid with temperature variations.The return current and the self-generated electric and magnetic fields are obtained by combining Ampère's law without the displacement current,the resistive Ohm's law and Faraday's law.The equations are solved in two-dimensional cylindrical geometry with rotational symmetry on a regular grid,with centered spatial differencing and first-order implicit time differencing.The algorithms implemented in the code are described,and a numerical experiment is performed for an electron beam with Maxwellian distribution ejected into a uniform deuterium-tritium plasma target.

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

    International Nuclear Information System (INIS)

    Emerging interest in utilizing the transverse coherence properties of thermal energy atomic and molecular beams motivates the development of ionization detectors with near unit detection efficiency and adequate spatial resolution to resolve interference fringes of submicron dimension. We demonstrate that a field ionization tip coupled to a charged particle detector meets these requirements. We have systematically studied the current-voltage relationship for field ionization of helium using tungsten tips in diffuse gas and in a supersonic helium beam. For all 16 tips used in this study, the dependence of ion current on voltage for tips of fixed radius was found to differ from that for tips held at constant surface electric field. A scaling analysis is presented to explain this difference. Ion current increased on average to the 2.8 power of voltage for a tip at fixed field and approximately fifth power of voltage for fixed radius for a liquid nitrogen cooled tip in room temperature helium gas. For the helium beam, ion current increased as 2.2 power of voltage with constant surface field. The capture region of the tips was found to be up to 0.1 μm2 for diffuse gas and 0.02 μm2 in the beam. Velocity dependence and orientation of tip to beam were also studied

  12. A Fast Non Intercepting Linac Electron Beam Position and Current Monitor

    DEFF Research Database (Denmark)

    Hansen, Jørgen-Walther; Wille, Mads

    A non-intercepting beam monitor consisting of four detecting loops is used to determine the spatial postion and current of a pulsed beam from an electron linear accelerator. The monitor detects the magnetic field radiated by the substructure of the electron bunches created by the accelerating...... microwave. The detecting loops are interconnected two by two, by means of two coaxial hybrid junctions, the two sets positioned perpendicular to each other. By means of the two signals from the diametrically positioned detecting loops, a good spatial displacement and current monitoring sensitivity are...

  13. Radiation damage in single crystal CVD diamond material investigated with a high current Au beam

    International Nuclear Information System (INIS)

    Single-crystal Chemical Vapor Deposition (ScCVD) diamond based prototype detectors have been constructed for the high current heavy ion experiments HADES and CBM at the future FAIR facility at GSI Darmstadt. Their properties have been studied with a high current density beam (about 2-3 x 106/s/mm2) of 1.25 A GeV Au ions. Details of the design, the intrinsic properties of the detectors and their performance after irradiation with such beam are reported.

  14. Effects of a dielectric material in an ion source on the ion beam current density and ion beam energy

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, Y., E-mail: yutaka-fujiwara@aist.go.jp; Sakakita, H.; Nakamiya, A. [Department of Engineering Mechanics and Energy, University of Tsukuba, Ibaraki 305-8577 (Japan); Innovative Plasma Processing Group, National Institute of Advanced Industrial Science and Technology (AIST), Ibaraki 305-8568 (Japan); Hirano, Y.; Kiyama, S. [Innovative Plasma Processing Group, National Institute of Advanced Industrial Science and Technology (AIST), Ibaraki 305-8568 (Japan)

    2016-02-15

    To understand a strong focusing phenomenon that occurs in a low-energy hydrogen ion beam, the electron temperature, the electron density, and the space potential in an ion source with cusped magnetic fields are measured before and after the transition to the focusing state using an electrostatic probe. The experimental results show that no significant changes are observed before or after the transition. However, we found unique phenomena that are characterized by the position of the electrostatic probe in the ion source chamber. Specifically, the extracted ion beam current density and energy are obviously enhanced in the case where the electrostatic probe, which is covered by a dielectric material, is placed close to an acceleration electrode.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wheat, Jr., Robert Mitchell [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dalmas, Dale A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dale, Gregory E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-08-11

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

  16. Microcontroller based four-channel current readout unit for beam slit monitor

    International Nuclear Information System (INIS)

    This paper describes the design and development of a microcontroller based four-channel current readout unit for Beam Slit Monitor (BSM) installed in Transport Line-1 of Indus Accelerator Complex. BSM is a diagnostic device consisting of two horizontal and two vertical blades, which can be moved independently in to the beam pipe to cut the beam transversely. The readout unit employs switched integrators with reset, hold and select switches and timing and control unit. It integrates the current output of the four blades of BSM and produces an output corresponding to the beam charge intercepted by the blade. The integrator outputs are then multiplexed and digitized using 12-bit ADC. Acquired digital data from ADC is stored into on-chip RAM of the microcontroller. The readout sequence is synchronized with the Microtron beam-timing signal. The timing of integration, hold and reset cycles is controlled by the microcontroller. The unit is connected on a serial link to the host computer in main control room. This unit has been integrated with the BSM system and is being used to obtain the electron beam profile. (author)

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

    Science.gov (United States)

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

    2012-12-01

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

  18. A Particle In Cell code development for high current ion beam transport and plasma simulations

    CERN Document Server

    Joshi, N

    2016-01-01

    A simulation package employing a Particle in Cell (PIC) method is developed to study the high current beam transport and the dynamics of plasmas. This package includes subroutines those are suited for various planned projects at University of Frankfurt. In the framework of the storage ring project (F8SR) the code was written to describe the beam optics in toroidal magnetic fields. It is used to design an injection system for a ring with closed magnetic field lines. The generalized numerical model, in Cartesian coordinates is used to describe the intense ion beam transport through the chopper system in the low energy beam section of the FRANZ project. Especially for the chopper system, the Poisson equation is implemented with irregular geometries. The Particle In Cell model is further upgraded with a Monte Carlo Collision subroutine for simulation of plasma in the volume type ion source.

  19. Supershort electron beam and voluminous heavy-current air discharge at atmospheric pressure

    International Nuclear Information System (INIS)

    The conditions of the electron beam and voluminous discharge formation in the air at the atmospheric pressure and subnanosecond pulse tension front are studied. It is shown that the electron beam in the gaseous diode originates at the pulse tension front over time of ∼ 0.5 ns and has duration at the semiheight of ≤0.4 ns. The electron beam with the electrons average energy of 60-80 keV and current amplitude of ≥70 A is obtained. It is assumed that the electron beam is formed from the electron avalanches, originating in the gap on the account of the gas ionization by fast electrons at achieving the critical field between the expanding plasma cloud front and anode

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

    Science.gov (United States)

    Katsura, Ichiro

    1998-06-01

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