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Sample records for fast icrf antenna

  1. Taming the ICRF Antenna - Plasma Edge Interaction using Novel Field-Aligned ICRF Antenna on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Lin, Yijun

    2014-10-01

    For ICRF antenna utilization in future fusion reactors, taming the antenna-plasma edge interaction while robustly coupling RF power is a critical challenge. Using a novel field-aligned (FA) ICRF antenna where the antenna straps are perpendicular to the total magnetic field, we have shown dramatically improved ICRF antenna performance. The FA antenna has significantly reduced antenna impurity sources, core impurity contamination and radiated power compared to conventional toroidally aligned antennas. The FA antenna also has load tolerance to plasma transients and significantly reduced RF-enhanced heat flux. The emerging physics picture is that the FA antenna minimizes generation of slow wave fields (E//B polarization). This reduction in slow wave lowers the local RF sheath around the ICRF antenna, and thus lowers the impurity source at local antenna structure. Simplified antenna simulations show a strong reduction in slow wave fields. The reduction of the slow wave field also impacts the antenna load tolerance. With the slow wave present, the antenna impedance is strongly modified by the slow wave coupling between antenna straps and this coupling is dependent upon the local density. With reduced slow wave coupling, the antenna reactive impedance is defined by the strap geometry and independent of the plasma whereas the real impedance is determined by the fast wave coupling. Experimentally we have found that the FA antenna loading has similar trends versus plasma current and densities to TA antennas, but the FA antenna reflection coefficient has significantly reduced variation, particularly during L-H and H-L transitions, and ELMs. Further comparisons of the FA and TA antennas are underway with an extensive array of diagnostics to characterize the RF plasma edge interaction and the latest results will be presented. Supported by US DoE awards DE-FC02-99ER54512 at MIT.

  2. Advanced ICRF antenna design for R-TOKAMAK

    NASA Astrophysics Data System (ADS)

    Kako, E.; Ando, R.; Ichimura, M.; Ogawa, Y.; Amano, T.; Watari, T.

    1986-01-01

    The advanced ICRF antennas designed for the R-TOKAMAK (a proposal in the Institute of Plasma Physics, Nagoya University) are described. They are a standard loop antenna and a panel heater antenna for fast wave heating, and a waveguide antenna for ion Bernstein wave heating. The standard loop antenna is made of Al-alloy and has a simple structure to install because of radioactivation by D-T neutrons. For high power heating, a new type antenna called Panel heater antenna is proposed. It has a wide radiation area and is able to select a parallel wave number k. The field pattern of the panel heater antenna is measured. The feasibility of the waveguide antenna is discussed for ion Bernstein wave heating. The radiation from the aperture of the double ridge waveguide is experimentally estimated with a load simulating the plasma.

  3. The ITER ICRF Antenna Design with TOPICA

    NASA Astrophysics Data System (ADS)

    Milanesio, Daniele; Maggiora, Riccardo; Meneghini, Orso; Vecchi, Giuseppe

    2007-11-01

    TOPICA (Torino Polytechnic Ion Cyclotron Antenna) code is an innovative tool for the 3D/1D simulation of Ion Cyclotron Radio Frequency (ICRF), i.e. accounting for antennas in a realistic 3D geometry and with an accurate 1D plasma model [1]. The TOPICA code has been deeply parallelized and has been already proved to be a reliable tool for antennas design and performance prediction. A detailed analysis of the 24 straps ITER ICRF antenna geometry has been carried out, underlining the strong dependence and asymmetries of the antenna input parameters due to the ITER plasma response. We optimized the antenna array geometry dimensions to maximize loading, lower mutual couplings and mitigate sheath effects. The calculated antenna input impedance matrices are TOPICA results of a paramount importance for the tuning and matching system design. Electric field distributions have been also calculated and they are used as the main input for the power flux estimation tool. The designed optimized antenna is capable of coupling 20 MW of power to plasma in the 40 -- 55 MHz frequency range with a maximum voltage of 45 kV in the feeding coaxial cables. [1] V. Lancellotti et al., Nuclear Fusion, 46 (2006) S476-S499

  4. ICRF antenna performance on Tore Supra

    NASA Astrophysics Data System (ADS)

    Goulding, R. H.; Carter, M. D.; Harris, J. H.; Hoffman, D. J.; Hogan, J. T.; Ryan, P. M.; Beaumont, B.; Bremond, S.; Hutter, T.

    1997-04-01

    Resonant double loop (RDL) ion cyclotron range of frequencies (ICRF) Antennas have operated on Tore Supra at power levels up to ˜3.5 MW per 2-element launcher. The RDL configuration is of particular interest because it has operated at high power densities (15 MW/m2 on Tore Supra) and is the topology chosen for the ITER ICRF launchers. Two Faraday shield designs are in use which produce different loading for nearly identical antenna radial positions, and different heating patterns on antenna surfaces due to rf/edge plasma interaction. Loading and maximum antenna voltage for a given power level have been found to vary between the different antennas in a frequency dependent manner. This behavior has been analyzed using a lossy transmission model. In addition, antenna surface heating patterns have been found to be highly phase dependent and reproducible over time. Strong localized power fluxes are often observed to determine the launcher power limit rather than internal voltages and currents.

  5. First results with 3-strap ICRF antennas in ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Bobkov, V.; Braun, F.; Dux, R.; Herrmann, A.; Faugel, H.; Fünfgelder, H.; Kallenbach, A.; Neu, R.; Noterdaeme, J.-M.; Ochoukov, R.; Pütterich, Th.; Tuccilo, A.; Tudisco, O.; Wang, Y.; Yang, Q.; ASDEX Upgrade team

    2016-08-01

    The 3-strap antennas in ASDEX Upgrade allow ICRF operation with low tungsten (W) content in the confined plasma with W-coated antenna limiters. With the 3-strap antenna configuration, the local W impurity source at the antenna is drastically reduced and the core W concentration is similar to that of the boron coated 2-strap antenna at a given ICRF power. Operation of the 3-strap antennas with the power ratio between the central and the outer straps of 1.5:1 and 2:1 is adopted to minimize the ICRF-specific W release.

  6. On the JET ITER-Like ICRF antenna and implications for the ICRF system for ITER

    NASA Astrophysics Data System (ADS)

    Durodie, Frederic; Nightingale, Mark

    2009-11-01

    A new ``ITER-Like'' Ion Cyclotron Resonance Frequency (ICRF) antenna was installed on the JET tokamak in 2007 and extensively operated on plasma since May 2008 for a wide range of conditions (frequencies: 33, 42 and 47 MHz, L- and ELMy H-mode plasmas, antenna strap - plasma separatrix distances from 9 to 17 cm). Aspects relating to the potential performance and design of the ITER system, will be discussed: (i) the wave coupling performance and validation of the TOPICA modelling code used to predict the coupled power in ITER; (ii) the operation at high coupled power density (up to 6.2 MW/m^2 in L-mode, 4.1 MW/m^2 in H-mode) and high RF voltage on the antenna structure (up to 42 kV); (iii) the coupling of ICRF power during fast variations (ms) in coupling occurring during ELMs and (iv) antenna control in the presence of high mutual coupling between antenna straps.

  7. Performance assessment of the ITER ICRF antenna

    NASA Astrophysics Data System (ADS)

    Durodié, F.; Vrancken, M.; Bamber, R.; Colas, L.; Dumortier, P.; Hancock, D.; Huygen, S.; Lockley, D.; Louche, F.; Maggiora, R.; Milanesio, D.; Messiaen, A.; Nightingale, M. P. S.; Shannon, M.; Tigwell, P.; van Schoor, M.; Wilson, D.; Winkler, K.; Cycle Team

    2014-02-01

    ITER's Ion Cyclotron Range of Frequencies (ICRF) system [1] comprises two antenna launchers designed by CYCLE (a consortium of European associations listed in the author affiliations above) on behalf F4E for the ITER Organisation (IO), each inserted as a Port Plug (PP) into one of ITER's Vacuum Vessel (VV) ports. Each launcher is an array of 4 toroidal by 6 poloidal RF current straps specified to couple up to 20 MW in total to the plasma in the frequency range of 40 to 55 MHz but limited to a maximum system voltage of 45 kV and limits on RF electric fields depending on their location and direction with respect to respectively the torus vacuum and the toroidal magnetic field. A crucial aspect of coupling ICRF power to plasmas is the knowledge of the plasma density profiles in the Scrape-Off Layer (SOL) and the location of the RF current straps with respect to the SOL. The launcher layout and details were optimized and its performance estimated for a worst case SOL provided by the IO. The paper summarizes the estimated performance obtained within the operational parameter space specified by IO. Aspects of the RF grounding of the whole antenna PP to the VV port and the effect of the voids between the PP and the Blanket Shielding Modules (BSM) surrounding the antenna front are discussed.

  8. A new radiation stripline ICRF antenna design for EAST Tokamak

    SciTech Connect

    Qin, C. M.; Zhao, Y. P.; Wan, B. N.; Li, J.; Zhang, X. J.; Yang, Q. X.; Yuan, S.; Braun, F.; Notedame, J.-M.; Kasahara, H.; Collaboration: ICRF Team on EAST

    2014-02-12

    A new type of toroidal long Radiation Stripline Antenna (RSA) is presented, which can effectively improve antenna radiation, leading in reduction of max voltage on transmission line and decrease of the sensitivity to ELM's of the ICRF system at some frequencies. Based on the new concept, a 4-straps RSA is proposed for EAST device. Using 3-D computing simulator code (HFSS), RF current distribution, S-parameters and electromagnetic field distribution on and near the RSA ICRF antenna are analyzed and compared with present ICRF antenna on EAST.

  9. Development of impedance matching technologies for ICRF antenna arrays

    SciTech Connect

    Pinsker, R.I.

    1998-03-01

    All high power ICRF heating systems include devices for matching the input impedance of the antenna array to the generator output impedance. For most types of antennas used, the input impedance is strongly time-dependent on timescales as rapid as 10-4 s, while the rf generators used are capable of producing full power only into a stationary load impedance. Hence, the dynamic response of the matching method is of great practical importance. In this paper, world-wide developments in this field over the past decade are reviewed. These techniques may be divided into several classes. The edge plasma parameters that determine the antenna array`s input impedance may be controlled to maintain a fixed load impedance. The frequency of the rf source can be feedback controlled to compensate for changes in the edge plasma conditions, or fast variable tuning elements in the transmission line between the generator output and the antenna input connections can provide the necessary time-varying impedance transformation. In lossy passive schemes, reflected power due to the time-varying impedance of the antenna array is diverted to a dummy load. Each of these techniques can be applied to a pre-existing antenna system. If a new antenna is to be designed, recent advances allow the antenna array to have the intrinsic property of presenting a constant load to the feeding transmission lines despite the varying load seen by each antenna in the array.

  10. Modeling of the EAST ICRF antenna with ICANT Code

    SciTech Connect

    Qin Chengming; Zhao Yanping; Colas, L.; Heuraux, S.

    2007-09-28

    A Resonant Double Loop (RDL) antenna for ion-cyclotron range of frequencies (ICRF) on Experimental Advanced Superconducting Tokamak (EAST) is under construction. The new antenna is analyzed using the antenna coupling code ICANT which self-consistently determines the surface currents on all antenna parts. In this work, the modeling of the new ICRF antenna using this code is to assess the near-fields in front of the antenna and analysis its coupling capabilities. Moreover, the antenna reactive radiated power computed by ICANT and shows a good agreement with deduced from Transmission Line (TL) theory.

  11. Modeling of the EAST ICRF antenna with ICANT Code

    NASA Astrophysics Data System (ADS)

    Qin, Chengming; Zhao, Yanping; Colas, L.; Heuraux, S.

    2007-09-01

    A Resonant Double Loop (RDL) antenna for ion-cyclotron range of frequencies (ICRF) on Experimental Advanced Superconducting Tokamak (EAST) is under construction. The new antenna is analyzed using the antenna coupling code ICANT which self-consistently determines the surface currents on all antenna parts. In this work, the modeling of the new ICRF antenna using this code is to assess the near-fields in front of the antenna and analysis its coupling capabilities. Moreover, the antenna reactive radiated power computed by ICANT and shows a good agreement with deduced from Transmission Line (TL) theory.

  12. Heating profiles on ICRF antenna Faraday shields

    SciTech Connect

    Taylor, D.J.; Baity, F.W.; Hahs, C.L.; Riemer, B.W.; Ryan, P.M.; Williamson, D.E.

    1991-01-01

    A conceptual design for an uncooled Faraday shield for the BPX ion cyclotron resonance heating (ICRH) antenna, which should withstand the proposed long-pulse operation, has been completed. A high-heat-flux, uncooled Faraday shield has also been designed for the fast-wave current drive (FWCD) antenna on D3-D. For both components, the improved understanding of the heating profiles made it possible to design for heat fluxes that would otherwise have been too close to mechanically established limits. The analytical effort is described in detail, with emphasis on the design work for the BPX ICRH antenna conceptual design and for the replacement Faraday shield for the D3-D FWCD antenna. Results of analyses are shown, and configuration issues involved in component modeling are discussed. 3 refs., 6 figs., 2 tabs.

  13. Analysis of the Tore Supra ICRF antenna with TOPICA

    NASA Astrophysics Data System (ADS)

    Milanesio, D.; Lancellotti, V.; Colas, L.; Maggiora, R.; Kyrytsya, V.; Vecchi, G.

    2007-04-01

    The Tore Supra (CEA) antenna for the ion cyclotron range of frequencies (ICRF) is a so-called resonant double loop antenna with internal matching capacitors. The required capacitance range is crucial for antenna and the tuning-and-matching network design. The capacitance value for a given discharge is also important for antenna operation. We discuss a method to accurately predict the tuning capacitance values in the presence of plasma operation and for efficiently accounting for the capacitors in the performance analysis. The presented method relies on the use of the TOPICA code, a numerical suite developed for prediction and analysis of modern ICRF antenna systems; it is able to handle antennas with a realistic 3D geometry and an accurate 1D plasma model. Very good agreement with the experimental capacitance values is found using TOPICA, providing further experimental validation of the computational algorithm and physics model.

  14. Assessment of ICRF Antenna Performance in Alcator C-Mod

    SciTech Connect

    G. Schilling; S.J. Wukitch; Y. Lin; N. Basse; P.T. Bonoli; E. Edlund; L. Lin; A. Parisot; M. Porkolab

    2004-08-10

    The Alcator C-Mod has presented a challenge to install high-power ICRF antennas in a tight space. Modifications have been made to the antenna plasma-facing surfaces and the internal current-carrying structure in order to overcome performance limitations. At the present time, the antennas have exceeded 5 MW into plasma with heating phasing, up to 2.7 MW with current-drive phasing, with good efficiency and no deleterious effects

  15. Assessment of a field-aligned ICRF antenna

    SciTech Connect

    Wukitch, S. J.; Brunner, D.; Ennever, P.; Garrett, M. L.; Hubbard, A.; Labombard, B.; Lau, C.; Lin, Y.; Lipschultz, B.; Miller, D.; Ochoukov, R.; Porkolab, M.; Reinke, M. L.; Terry, J. L.

    2014-02-12

    Impurity contamination and localized heat loads associated with ion cyclotron range of frequency (ICRF) antenna operation are among the most challenging issues for ICRF utilization.. Another challenge is maintaining maximum coupled power through plasma variations including edge localized modes (ELMs) and confinement transitions. Here, we report on an experimental assessment of a field aligned (FA) antenna with respect to impurity contamination, impurity sources, RF enhanced heat flux and load tolerance. In addition, we compare the modification of the scrape of layer (SOL) plasma potential of the FA antenna to a conventional, toroidally aligned (TA) antenna, in order to explore the underlying physics governing impurity contamination linked to ICRF heating. The FA antenna is a 4-strap ICRF antenna where the current straps and antenna enclosure sides are perpendicular to and the Faraday screen rods are parallel to the total magnetic field. In principle, alignment with respect to the total magnetic field minimizes integrated E∥ (electric field along a magnetic field line) via symmetry. Consistent with expectations, we observed that the impurity contamination and impurity source at the FA antenna are reduced compared to the TA antenna. In both L and H-mode discharges, the radiated power is 20–30% lower for a FA-antenna heated discharge than a discharge heated with the TA-antennas. Further we observe that the fraction of RF energy deposited upon the antenna is less than 0.4 % of the total injected RF energy in dipole phasing. The total deposited energy increases significantly when the FA antenna is operated in monopole phasing. The FA antenna also exhibits an unexpected load tolerance for ELMs and confinement transitions compared to the TA antennas. However, inconsistent with expectations, we observe RF induced plasma potentials to be nearly identical for FA and TA antennas when operated in dipole phasing. In monopole phasing, the FA antenna has the highest plasma

  16. ITER Reference ICRF Antenna Analysis with TOPICA Code

    NASA Astrophysics Data System (ADS)

    Milanesio, Daniele; Maggiora, Riccardo; Lancellotti, Vito; Kyrytsya, Volodymyr; Vecchi, Giuseppe

    2006-10-01

    TOPICA (Torino Polytechnic Ion Cyclotron Antenna) code is an innovative tool for the 3D/1D simulation of Ion Cyclotron Radio Frequency (ICRF), i.e. accounting for antennas in a realistic 3D geometry and with an accurate 1D plasma model [1]. The TOPICA suite, validated against measurements and data of mock-ups and existing antennas, has been proved to be a reliable tool for antennas performance prediction during operating conditions. The first part of this work reports on an extensive set of comparisons between TOPICA code and RANT3D code [2] results adopting different geometrical model of an ITER Reference ICRF antenna. Furthermore, in the second part, a detailed analysis of the performances of an ITER-like ICRF antenna geometry has been carried out, underlining the strong dependence and asymmetries of antenna input parameters due to plasma conditions. Electric current distribution on conductors in the vacuum region and electric field distribution in the vacuum region and at the interface with plasma edge are shown as well. [1] V. Lancellotti et al., Nucl. Fusion, 46 (2006) S476-S499 newline [2] M. D. Carter et al., Nucl. Fusion, 36 (1996) S209

  17. ICRF heating on TFTR with the ORNL antenna

    SciTech Connect

    Hoffman, D.J.; Gardner, W.L.; Ryan, P.M.; Greene, G.J.; Hosea, J.C.; Wilson, J.R.; Stevens, J.E.

    1989-01-01

    Initial ion cyclotron range of frequencies (ICRF) heating experiments on TFTR began in the summer of 1988. Although we were in the commissioning stage for much of the equipment, some plasma coupling measurements were made in the fall. This paper is focused on the results from the Bay L antenna. 3 refs., 3 figs., 1 tab.

  18. Characterization of local heat fluxes around ICRF antennas on JET

    NASA Astrophysics Data System (ADS)

    Campergue, A.-L.; Jacquet, P.; Bobkov, V.; Milanesio, D.; Monakhov, I.; Colas, L.; Arnoux, G.; Brix, M.; Sirinelli, A.; JET-EFDA Contributors

    2014-02-01

    When using Ion Cyclotron Range of Frequency (ICRF) heating, enhanced power deposition on Plasma-Facing Components (PFCs) close to the antennas can occur. Experiments have recently been carried out on JET with the new ITER-Like-Wall (ILW) to characterize the heat fluxes on the protection of the JET ICRF antennas, using Infra-Red (IR) thermography measurement. The measured heat flux patterns along the poloidal limiters surrounding powered antennas were compared to predictions from a simple RF sheath rectification model. The RF electric field, parallel to the static magnetic field in front of the antenna, was evaluated using the TOPICA code, integrating a 3D flattened model of the JET A2 antennas. The poloidal density variation in front of the limiters was obtained from the mapping of the Li-beam or edge reflectometry measurements using the flux surface geometry provided by EFIT equilibrium reconstruction. In many cases, this simple model can well explain the position of the maximum heat flux on the different protection limiters and the heat-flux magnitude, confirming that the parallel RF electric field and the electron plasma density in front of the antenna are the main driving parameters for ICRF-induced local heat fluxes.

  19. Characterization of local heat fluxes around ICRF antennas on JET

    SciTech Connect

    Campergue, A.-L.; Jacquet, P.; Monakhov, I.; Arnoux, G.; Brix, M.; Sirinelli, A.; Milanesio, D.; Colas, L.; Collaboration: JET-EFDA Contributors

    2014-02-12

    When using Ion Cyclotron Range of Frequency (ICRF) heating, enhanced power deposition on Plasma-Facing Components (PFCs) close to the antennas can occur. Experiments have recently been carried out on JET with the new ITER-Like-Wall (ILW) to characterize the heat fluxes on the protection of the JET ICRF antennas, using Infra-Red (IR) thermography measurement. The measured heat flux patterns along the poloidal limiters surrounding powered antennas were compared to predictions from a simple RF sheath rectification model. The RF electric field, parallel to the static magnetic field in front of the antenna, was evaluated using the TOPICA code, integrating a 3D flattened model of the JET A2 antennas. The poloidal density variation in front of the limiters was obtained from the mapping of the Li-beam or edge reflectometry measurements using the flux surface geometry provided by EFIT equilibrium reconstruction. In many cases, this simple model can well explain the position of the maximum heat flux on the different protection limiters and the heat-flux magnitude, confirming that the parallel RF electric field and the electron plasma density in front of the antenna are the main driving parameters for ICRF-induced local heat fluxes.

  20. Design of an ICRF plasma thruster antenna by TOPICA

    NASA Astrophysics Data System (ADS)

    Vecchi, Giuseppe; Lancellotti, Vito; Maggiora, Riccardo

    2006-10-01

    A typical RF plasma thruster is comprised of an RF plasma source, an open-ended magnetic confinement device, an RF acceleration unit and a magnetic nozzle. The usual choice for the acceleration is to employ the Ion-Cyclotron resonance frequency (ICRF), a well established technology in fusion experiments for transferring large RF powers to magnetized plasmas. To help design RF thruster ICRF antennas, TOPICA (Torino Polytechnic Ion Cyclotron Antenna) code [1] has been recently extended to handle cylindrically symmetric plasmas. The latter entailed developing a wholly new module of TOPICA charged with the task of solving Maxwell's equations in cylindrical magnetized warm plasmas and yielding the Green's functionY (m,kz), i.e. the relationship at the air-plasma interface between the transverse magnetic and electric fields in the spectral (wavenumber) domain. The approach to the problem of determining the antenna input impedance relies on an integral-equation formulation for the self-consistent evaluation of the current distribution on the conductors. This work reports on TOPICA evolution and presents the design of an RF thruster ICRF antenna. *V. Lancellotti et al., Nucl. Fusion, 46 (2006) S476-S499

  1. Validation of an ICRF ITER-Like Antenna on Tore Supra

    NASA Astrophysics Data System (ADS)

    Argouarch, A.; Vulliez, K.; Bosia, G.; Berger-By, G.; Bremond, S.; Colas, L.; Lombard, G.; Mendes, A.; Millon, L.; Mollard, P.; Bottolier-Curtet, H.; Magne, R.; Volpe, D.; Beaumont, B.; Bécoulet, A.; Clairet, F.; Ekedahl, A.; Elkhaldi, M.; Gunn, J.; Hoang, G. T.

    2009-11-01

    A prototype of an ICRF antenna based on the load-resilient electrical layout foreseen for ITER has been built at CEA-Cadarache [1]. It consists of a two resonant double loop (RDL) based on the conjugate-T concept proposed for the ITER ICRF array arranged toroidally in a close package. The antenna conditioning and commissioning have been successfully performed to validate the load resilience and the heating capability at the end of 2007. On Tore Supra despite unexciting ELMs, the load resilience studies have been conducted in L-mode by mean of slow variations of the plasma position and fast transient variations with both pellet injection and Supersonic Molecular Beam Injection (SMBI). The capability to maintain the RF power on the ITER-like antenna has been done successfully contrary to the classical ICRF antenna during the SMBI shots, in which the corresponding transient coupling resistance increased by a factor 3-4. In term of coupled power, a maximum power density of 6.6 MW/m2 is reached.

  2. Field-aligned ICRF antenna design for EAST

    NASA Astrophysics Data System (ADS)

    Wukitch, S. J.; Lin, Y.; Qin, C.; Zhang, X.; Beck, W.; Koert, P.; Zhou, L.

    2015-12-01

    For ion cyclotron range of frequency (ICRF), a number of physics and technological challenges remain for steady state, toroidal devices. Among the most critical is maintaining good coupling and maximizing the coupled power through plasma variations including edge localized modes (ELMs) and confinement transitions. As pulse length increases, enhanced localized heat loads associated with antenna operation can challenge antenna integrity. In addition, ICRF impurity sources and contamination need to be minimized to enable effective plasma heating. Here, we report on a four strap field aligned (FA) antenna design for the EAST tokamak. A FA antenna is an antenna where the current straps and antenna side enclosure are perpendicular to the total magnetic field while the Faraday screen rods are parallel to the total magnetic field. In C-Mod, a FA antenna has been shown to be inherently load tolerant which allows for robust power delivery to the plasma. Furthermore, the RF enhanced heat flux and antenna impurity source were nearly eliminated. For both L and H-mode discharges, the core impurity contamination is 20-30% lower but not eliminated. The emerging physics understanding is that the local RF impurity sources and RF enhanced heat flux is reduced due to the geometric alignment of the FA antenna while impurity contamination is a result of far field sheaths. An important aspect of antenna design is to identify a core absorption scenario that is characterized by strong single pass absorption for a broad range of target discharges. To maximize power coupling, the antenna spectrum needs to balance the k|| needed for strong single pass absorption and high coupling efficiency through evanescent layer. The latest design for a FA four strap adapted to EAST device is balance between geometrical constraints and physics requirements.

  3. Benchmark simulations of ICRF antenna coupling

    NASA Astrophysics Data System (ADS)

    Louche, F.; Lamalle, P. U.; Messiaen, A. M.; Van Compernolle, B.; Milanesio, D.; Maggiora, R.

    2007-09-01

    The paper reports on ongoing benchmark numerical simulations of antenna input impedance parameters in the ion cyclotron range of frequencies with different coupling codes: CST Microwave Studio, TOPICA and ANTITER 2. In particular we study the validity of the approximation of a magnetized plasma slab by a dielectric medium of suitably chosen permittivity. Different antenna models are considered: a single-strap antenna, a 4-strap antenna and the 24-strap ITER antenna array. Whilst the diagonal impedances are mostly in good agreement, some differences between the mutual terms predicted by Microwave Studio and TOPICA have yet to be resolved.

  4. Benchmark simulations of ICRF antenna coupling

    SciTech Connect

    Louche, F.; Lamalle, P. U.; Messiaen, A. M.; Compernolle, B. van; Milanesio, D.; Maggiora, R.

    2007-09-28

    The paper reports on ongoing benchmark numerical simulations of antenna input impedance parameters in the ion cyclotron range of frequencies with different coupling codes: CST Microwave Studio, TOPICA and ANTITER 2. In particular we study the validity of the approximation of a magnetized plasma slab by a dielectric medium of suitably chosen permittivity. Different antenna models are considered: a single-strap antenna, a 4-strap antenna and the 24-strap ITER antenna array. Whilst the diagonal impedances are mostly in good agreement, some differences between the mutual terms predicted by Microwave Studio and TOPICA have yet to be resolved.

  5. ICRF antenna matching system with ferrite tuners for the Alcator C-Mod tokamak

    NASA Astrophysics Data System (ADS)

    Lin, Y.; Binus, A.; Wukitch, S. J.; Koert, P.; Murray, R.; Pfeiffer, A.

    2015-12-01

    Real-time fast ferrite tuning (FFT) has been successfully implemented on the ICRF antennas on Alcator C-Mod. The former prototypical FFT system on the E-port 2-strap antenna has been upgraded using new ferrite tuners that have been designed specifically for the operational parameters of the Alcator C-Mod ICRF system (˜ 80 MHz). Another similar FFT system, with two ferrite tuners and one fixed-length stub, has been installed on the transmission line of the D-port 2-strap antenna. These two systems share a Linux-server-based real-time controller. These FFT systems are able to achieve and maintain the reflected power to the transmitters to less than 1% in real time during the plasma discharges under almost all plasma conditions, and help ensure reliable high power operation of the antennas. The innovative field-aligned (FA) 4-strap antenna on J-port has been found to have an interesting feature of loading insensitivity vs. plasma conditions. This feature allows us to significantly improve the matching for the FA J-port antenna by installing carefully designed stubs on the two transmission lines. The reduction of the RF voltages in the transmission lines has enabled the FA J-port antenna to deliver 3.7 MW RF power to plasmas out of the 4 MW source power in high performance I-mode plasmas.

  6. Validation of 3D/1D Analysis of ICRF Antennas

    NASA Astrophysics Data System (ADS)

    Milanesio, D.; Lancellotti, V.; Kyrytsya, V.; Maggiora, R.; Vecchi, G.; Parisot, A.; Wukitch, S. J.

    2004-11-01

    An innovative tool has been realized for the 3D/1D simulation of Ion Cyclotron Radio Frequency (ICRF), i.e. accounting for antennas in a realistic 3D geometry and with an accurate 1D plasma model. The approach to the problem is based on an integral-equation formulation for the self-consistent evaluation of the current distribution on the conductors. The environment has been subdivided in two coupled region: the plasma region and the vacuum region. The two problems are linked by means of electromagnetic current distribution on the aperture between the two regions. The plasma enters the formalism via a surface impedance matrix for this reason any plasma model can be used. The source term directly models the TEM mode of the coax feeding the antenna and the current in the coax is determined self-consistently, giving the input impedance/admittance of the antenna itself. The suite, called TOPICA, has been used in the design of various ICRF antennas and also for the performance prediction of the ALCATOR C-MOD D and E antenna. An extensive set of comparisons between measured and simulated antenna parameters during ALCATOR C-MOD operation will be presented.

  7. Detailed Modeling of Grounding Solutions for the ITER ICRF Antenna

    NASA Astrophysics Data System (ADS)

    Kyrytsya, V.; Dumortier, P.; Messiaen, A.; Louche, F.; Durodié, F.

    2011-12-01

    The excitation of non-TEM modes around the ITER ICRF antenna plug can considerably increase the level of RF voltages and currents on the ITER plug. First study of these modes and a solution to avoid them in the ITER ion cyclotron range of frequencies were reported in [1]. In this work a detailed analysis of electrical properties of the ITER ICRF antenna with the plug was studied for different grounding solutions with CST Microwave Studio® [2]. Conclusions of an earlier work [ 1 ] were confirmed on the detailed model of the antenna with the plug. Different grounding contacts (capacitive, galvanic and mixed capacitive-galvanic) as well as their distribution inside the plug gap were analyzed. It was shown that capacitive and mixed capacitive-galvanic grounding are less effective because they demand high values of the capacitance and are more sensitive to the frequency and antenna spectrum. In particular a galvanic grounding realized by the contacts put around the perimeter of the plug gap at lm behind the front face of the antenna is the most suitable solution from the electromagnetic point of view. An optimization of the layout and arrangement of the contacts in order to assess and optimize the current distribution on them is under way. Measurements on a scaled mock-up of the complete antenna and the plug are under way for modeling results confirmation.

  8. ICRF antenna modeling and simulation. Final report, March 1, 1993--May 31, 1996

    SciTech Connect

    1996-08-30

    SAIC has undergone a three year research and development program in support of the DOE Office of Fusion Energy`s (OFE) program in Ion Cyclotron Range of Frequencies (ICRF) heating of present, next generation, and future plasma fusion devices. The effort entailed advancing theoretical models and numerical simulation technology of ICRF physics and engineering issues associated predominately with, but not limited to, tokamak Ion Cyclotron Heating (ICH) and fast wave current drive (FWCD). Ion cyclotron heating and current drive is a central element in all current and planned large fusion experiments. In recent years, the variety of uses for ICRF systems has expanded, and includes the following: (1) Heating sufficient to drive plasma to ignition. (a) Second-harmonic T heating. (b) He{sup 3} minority heating. (2) Second-harmonic He{sup 4} heating in H plasma (for non-activated phase). (3) Detailed equilibrium profile control minority heating. (a) Ion minority (He{sup 3}) CD (for profile control on inside of plasma). (b) Ion minority (He{sup 3}) CD (for profile control on outside of plasma). (4) Ion-ion hybrid regime majority ion heating. (5) Electron current drive. (6) Mode conversion to drive current. (7) Deuterium minority heating. (8) Sawtooth instability stabilization. (9) Alpha particle parameter enhancement. (10) The generation of minority tails by ICRF to simulate D-T plasma particle physics in a deuterium plasma. Optimization of ICRF antenna performance for either heating or current drive depends critically on the complex balance and interplay between the plasma physics and the electromechanical system requirements. For example, ITER IC rf designs call for an IC. system frequency range from 20 MHz to 100 MHz. Additionally, antenna designs and operational modes that minimize impurity production and induced sheath formation may degrade current drive efficiency. Such effects have been observed in experiments involving it versus zero antenna phasing.

  9. High voltage test-stand research done on ICRF antenna elements of the high-harmonic fast-wave system of NSTX

    NASA Astrophysics Data System (ADS)

    Perkins, R. J.; Ahn, J.-W.; Bortolon, A.; Brunkhorst, C.; Ellis, R.; Fredd, E.; Greenough, N.; Hosea, J. C.; Kung, C.; Miller, D.

    2015-12-01

    The twelve-strap high-harmonic fast-wave (HHFW) antenna on NSTX has exhibited a high-voltage standoff around 25 kV during previous experimental campaigns; this standoff needs to be improved for increased power coupling. During the recent NSTX-U upgrade period, a test-stand was set up with two antenna straps along with Faraday screens for testing purposes. Using a diagnostic suite consisting of a fast camera, a residual gas analyzer, a pressure gage, high-voltage probes, and an infrared camera, several interesting discoveries were made, leading to possible improvements of the antenna RF voltage operation level. First, arcing was observed outside the Faraday shields towards the low-voltage ("grounded") end of the straps (faraday shield box ends); this arcing was successfully eliminated by installing an additional grounding point between the Faraday shield box and the vessel wall. Second, considerable outgassing was observed during the RF pulse and the amount of outgassing was found to decrease with increasing RF power, possibly indicative of multipacting. Finally, infrared camera measurements of heating on the Faraday shield assembly suggest that the return currents on the Faraday shield box are highly localized at the box sides and possibly account for the pressure increase observed. Computations of these RF currents using Microwave Studio show qualitative agreement with the heated regions. New grounding points between the antenna box and the vessel have been implemented in NSTX-U, where future tests will be done to determine if the high-voltage standoff has improved. Further antenna improvements will be sought through future experiments on the test stand.

  10. High Voltage Test-Stand Research Done on ICRF Antenna Elements of the High-Harmonic Fast-Wave System of NSTX

    SciTech Connect

    Perkins, R. J.; Ahn, J.W.; Bortolon, A.; Brunkhorst, C.; Ellis, R.; Fredd, E.; Greenough, Nevell; Hosea, J.; Kung, C. C.; Miller, D.

    2015-01-01

    The twelve-strap high-harmonic fast-wave (HHFW) antenna on NSTX has exhibited a high-voltage standoff around 25 kV during previous experimental campaigns; this standoff needs to be improved for increased power coupling. During the recent NSTX-U upgrade period, a test-stand was set up with two antenna straps along with Faraday screens for testing purposes. Using a diagnostic suite consisting of a fast camera, a residual gas analyzer, a pressure gage, high-voltage probes, and an infrared camera, several interesting discoveries were made, leading to possible improvements of the antenna RF voltage operation level. First, arcing was observed outside the Faraday shields towards the low-voltage ("grounded") end of the straps (faraday shield box ends); this arcing was successfully eliminated by installing an additional grounding point between the Faraday shield box and the vessel wall. Second, considerable outgassing was observed during the RF pulse and the amount of outgassing was found to decrease with increasing RF power, possibly indicative of multipacting. Finally, infrared camera measurements of heating on the Faraday shield assembly suggest that the return currents on the Faraday shield box are highly localized at the box sides and possibly account for the pressure increase observed. Computations of these RF currents using Microwave Studio show qualitative agreement with the heated regions. New grounding points between the antenna box and the vessel have been implemented in NSTX-U, where future tests will be done to determine if the high-voltage standoff has improved. Further antenna improvements will be sought through future experiments on the test stand.

  11. RF Voltage Measurements on ICRF Antennas

    NASA Astrophysics Data System (ADS)

    Bell, G. L.; Goulding, R. H.; Hoffman, D. J.; Wilgen, J. B.; Zhang, H. M.; Ryan, P. M.; Syed, G. M. S.; Kaye, A. S.

    1996-11-01

    Particle and heat flux on the plasma facing surfaces of high-power RF antennas used in fusion devices can result in damage to the antenna structures. High impedance capacitive probe measurements of the RF voltages on Faraday shields of several loop antennas indicate that voltages as high as 30% of the drive voltage can exist for 0/0 phasing (D.J. Hoffman, et al., AIP Conf. Proc. 355), 368 (Palm Spgs., CA, 1995).. These voltages can contribute to increased energy deposition on the antenna owing to increased RF sheath voltages. We report on continued efforts to understand the source and to control these RF voltages. E and B field distributions have been measured on the mock-up of the JET A2 antenna using standard B-dot probes and novel E-field probes positioned with a new automated scanning system. These data are compared with calculated fields from 3-D antenna models. The measurements demonstrate the dependency of the surface E-fields on the phasing of the strap currents and show the charge accumulation at the antenna top and bottom predicted by the models.

  12. ITER ICRF antenna analysis and optimization using the TOPICA code

    NASA Astrophysics Data System (ADS)

    Milanesio, D.; Maggiora, R.

    2010-02-01

    This paper documents the complete analysis and optimization of the ITER ion cyclotron range of frequency (ICRF) launcher using the TOPICA code, carried out in the frame of EFDA design activities. The possibility to simulate the detailed geometry of an ICRF antenna in front of a realistic plasma description and to obtain the antenna input parameters and the radiated near electric field distribution is of paramount importance to evaluate and predict the overall system performances. Upon starting from a reference geometry, we pursued a detailed electrical optimization of the IC launcher and we came out with a final geometry showing a remarkable increase in terms of power coupled to plasma. The optimization procedure involved the modification of different parts of the antenna, such as the horizontal septa, the coaxial cables, the coax-to-feeder transitions, the feeders, the strap and the grounding. Eventually, the optimized geometry has been the object of a comprehensive analysis, varying the working frequency, the plasma conditions and the poloidal and toroidal phasings between the feeding cables. The performances of the antenna have been appreciated not only in terms of input parameters or power coupled to plasma, but also by means of power spectra and with the evaluation of the RF potentials.

  13. 3D/1D Analysis of ICRF Antennas

    NASA Astrophysics Data System (ADS)

    Maggiora, Riccardo; Lancellotti, Vito; Vecchi, Giuseppe

    2003-10-01

    An innovative tool has been realized for the 3D/1D simulation of Ion Cyclotron Radio Frequency (ICRF), i.e. accounting for antennas in a realistic 3D geometry and with an accurate 1D plasma model. The approach to the problem is based on an integral-equation formulation for the self-consistent evaluation of the current distribution on the conductors. The environment has been subdivided in two coupled region: the plasma region and the vacuum region. The two problems are linked by means of a magnetic current (electric field) distribution on the aperture between the two regions. In the vacuum region all the calculations are executed in the spatial domain while in the plasma region an extraction in the spectral domain of some integrals is employed that permits to significantly reduce the integration support and to obtain a high numerical efficiency leading to the practical possibility of using a large number of sub-domain (rectangular or triangular) basis functions on each solid conductor of the system. The plasma enters the formalism of the plasma region via a surface impedance matrix; for this reason any plasma model can be used; at present the FELICE code has been adopted, that affords density and temperature profiles, and FLR effects. The source term directly models the TEM mode of the coax feeding the antenna and the current in the coax is determined self-consistently, giving the input impedance/admittance of the antenna itself. Calculation of field distributions (both magnetic and electric), useful for sheath considerations, is included. This tool has been implemented in a suite, called TOPICA, that is modular and applicable to ICRF antenna structures of arbitrary shape. This new simulation tool can assist during the detailed design phase and for this reason can be considered a "Virtual Prototyping Laboratory" (VPL). The TOPICA suite has been tested against assessed codes and against measurements and data of mock-ups and existing antennas. The VPL is being used in

  14. Theory and Practice in ICRF Antennas for Long Pulse Operation

    SciTech Connect

    Colas, L.; Bremond, S.; Mitteau, R.; Chantant, M.; Goniche, M.; Basiuk, V.; Bosia, G.; Gunn, J.P.

    2005-09-26

    Long plasma discharges on the Tore Supra (TS) tokamak were extended in 2004 towards higher powers and plasma densities by combined Lower Hybrid (LH) and Ion Cyclotron Range of Frequencies (ICRF) waves. RF pulses of 20sx8MW and 60sx4MW were produced. TS is equipped with 3 ICRF antennas, whose front faces are ready for CW operation. This paper reports on their behaviour over high power long pulses, as observed with infrared (IR) thermography and calorimetric measurements. Edge parasitic losses, although modest, are concentrated on a small surface and can raise surface temperatures close to operational limits. A complex hot spot pattern was revealed with at least 3 physical processes involved : convected power, electron acceleration in the LH near field, and a RF-specific phenomenon compatible with RF sheaths. LH coupling was also perturbed in the antenna shadow. This was attributed to RF-induced DC ExB0 convection. This motivated sheath modelling in two directions. First, the 2D topology of RF potentials was investigated in relation with the RF current distribution over the antenna, via a Green's function formalism and full-wave calculation using the ICANT code. In front of phased arrays of straps, convective cells were interpreted using the RF current profiles of strip line theory. Another class of convective cells, specific to antenna box corners, was evidenced for the first time. Within 1D sheath models assuming independent flux tubes, RF and rectified DC potentials are proportional. 2D fluid models couple nearby flux tubes via transverse polarisation currents. Unexpectedly this does not necessarily smooth RF potential maps. Peak DC potentials can even be enhanced. The experience gained on TS and the numerical tools are valuable for designing steady state high power antennas for next step devices. General rules to reduce RF potentials as well as concrete design options are discussed.

  15. Density profile sensitivity study of ASDEX Upgrade ICRF Antennas with the TOPICA code

    NASA Astrophysics Data System (ADS)

    Krivska, A.; Ceccuzzi, S.; Milanesio, D.; Bobkov, V.; Braun, F.; Maggiora, R.; Noterdaeme, J.-M.; Tuccillo, A. A.

    2011-12-01

    During operation of the ASDEX Upgrade (AUG) ion cyclotron radio frequency (ICRF) system, Tungsten (W)-coated poloidal limiters and structures connected along magnetic field lines to the antenna can be sources of W, which is attributed to sputtering by ions accelerated in radio frequency (RF) sheaths. In order to analyze and optimize the ICRF antenna performance, accurate and efficient simulation tools are necessary. TOPICA code was developed for analysis of ICRF antenna systems with plasma loading conditions modeled with ID FELICE code. This paper presents an initial comparative analysis of two AUG ICRF antennas for a set of model plasma density profiles (with varying density gradient and antenna cut-off distance). The antennas are presently installed in AUG and differ in that one was partially optimized using HFSS code to reduce E∥ near fields. Power transferred to plasma and sheath driving RF potentials are computed.

  16. Electromagnetic simulations of the ASDEX Upgrade ICRF Antenna with the TOPICA code

    NASA Astrophysics Data System (ADS)

    Krivska, A.; Milanesio, D.; Bobkov, V.; Braun, F.; Noterdaeme, J.-M.

    2009-11-01

    Accurate and efficient simulation tools are necessary to optimize the ICRF antenna design for a set of operational conditions. The TOPICA code was developed for performance prediction and for the analysis of ICRF antenna systems in the presence of plasma, given realistic antenna geometries. Fully 3D antenna geometries can be adopted in TOPICA, just as in available commercial codes. But while those commercial codes cannot operate with a plasma loading, the TOPICA code correctly accounts for realistic plasma loading conditions, by means of the coupling with 1D FELICE code. This paper presents the evaluation of the electric current distribution on the structure, of the parallel electric field in the region between the straps and the plasma and the computation of sheaths driving RF potentials. Results of TOPICA simulations will help to optimize and re-design the ICRF ASDEX Upgrade antenna in order to reduce tungsten (W) sputtering attributed to the rectified sheath effect during ICRF operation.

  17. Recent experiments on alternative dipole phasing with the JET A2 ICRF antennas

    SciTech Connect

    Lerche, E.; Messiaen, A.; Ongena, J.; Telesca, G.; Van Eester, D.; Weynants, R. R.; Bobkov, V.; Jacquet, P.; Mayoral, M.-L.; Monakhov, I.

    2009-11-26

    Using the JET A2 ICRF antennas, experiments were carried out to assess the performance of three different dipole phasing configurations relevant for the operation of the ICRF antenna in ITER. Three similar discharges with dipole (0{pi}0{pi}), 'symmetric dipole' (0{pi}{pi}0) and 'super dipole' (00{pi}{pi}) phasings were compared. In the 'super dipole' case, higher coupling was confirmed but lower heating efficiency and much stronger plasma wall interaction were observed, as corroborated, respectively, by the analysis of the diamagnetic energy response to the ICRF power steps and by the observation of a considerable temperature rise of the antenna limiters and septa in the 00{pi}{pi} case. These observations were found to be in line with simulations of the ICRF wave absorption and with High Frequency Structure Simulator (HFSS) modelling of the RF fields near the antenna.

  18. Commissioning of the ITER-like ICRF antenna for JET

    SciTech Connect

    Durodie, F.; Dumortier, P.; Huygen, S.; Jachmich, S.; Lerche, E.; Messiaen, A.; Ongena, J; Van Eester, D.; Vrancken, M.; Nightingale, M.; Berger-By, G.; Loarer, T.; Rimini, F.; Castano-Giraldo, C.; Caughman, John B.; Goulding, Richard Howell; Cocilovo, V.; Frigione, D.; Sozzi, C.; Hobrik, J.; Lamalle, Philippe; Nave, M. F. F.

    2009-06-01

    The new JET ion cyclotron resonance frequency (ICRF) ITER-like antenna (ILA), which was assembled during 2006, was commissioned on the JET RF testbed prior to installation on the JET torus. The 4 resonant double loops (RDL) of the ILA were tested at high power at 42 MHz up to 42 kV for 5 s in 10 min intervals. Low power matching studies using a saltwater load placed in front of the ILA have allowed testing and optimizing proposed matching algorithms on single RDLs, paired RDLs and finally on the full array. The upper limit of the frequency range of the ILA appears to be limited to 47 49 MHz due to the effect on the electrical lengths of the connection between the capacitors and the conjugate T point. Capacitor position scans have allowed obtaining the necessary data to confirm the RF model of the RDL which is necessary for the scattering matrix arc detection. The latter is deemed necessary in order to detect arcs at the low impedance conjugate T of the circuit. The antenna was installed onto JET during August 2007 and commissioning on plasma started May 2008. At present the commissioning of the ILA on JET is ongoing in a series of dedicated experimental campaigns.

  19. Estimation of sheath potentials in front of ASDEX upgrade ICRF antenna with SSWICH asymptotic code

    NASA Astrophysics Data System (ADS)

    Křivská, A.; Bobkov, V.; Colas, L.; Jacquot, J.; Milanesio, D.; Ochoukov, R.

    2015-12-01

    Multi-megawatt Ion Cyclotron Range of Frequencies (ICRF) heating became problematic in ASDEX Upgrade (AUG) tokamak after coating of ICRF antenna limiters and other plasma facing components by tungsten. Strong impurity influx was indeed produced at levels of injected power markedly lower than in the previous experiments. It is assumed that the impurity production is mainly driven by parallel component of Radio-Frequency (RF) antenna electric near-field E// that is rectified in sheaths. In this contribution we estimate poloidal distribution of sheath Direct Current (DC) potential in front of the ICRF antenna and simulate its relative variations over the parametric scans performed during experiments, trying to reproduce some of the experimental observations. In addition, relative comparison between two types of AUG ICRF antenna configurations, used for experiments in 2014, has been performed. For this purpose we use the Torino Polytechnic Ion Cyclotron Antenna (TOPICA) code and asymptotic version of the Self-consistent Sheaths and Waves for Ion Cyclotron Heating (SSWICH) code. Further, we investigate correlation between amplitudes of the calculated oscillating sheath voltages and the E// fields computed at the lateral side of the antenna box, in relation with a heuristic antenna design strategy at IPP Garching to mitigate RF sheaths.

  20. Estimation of sheath potentials in front of ASDEX upgrade ICRF antenna with SSWICH asymptotic code

    SciTech Connect

    Křivská, A.; Colas, L.; Milanesio, D.

    2015-12-10

    Multi-megawatt Ion Cyclotron Range of Frequencies (ICRF) heating became problematic in ASDEX Upgrade (AUG) tokamak after coating of ICRF antenna limiters and other plasma facing components by tungsten. Strong impurity influx was indeed produced at levels of injected power markedly lower than in the previous experiments. It is assumed that the impurity production is mainly driven by parallel component of Radio-Frequency (RF) antenna electric near-field E// that is rectified in sheaths. In this contribution we estimate poloidal distribution of sheath Direct Current (DC) potential in front of the ICRF antenna and simulate its relative variations over the parametric scans performed during experiments, trying to reproduce some of the experimental observations. In addition, relative comparison between two types of AUG ICRF antenna configurations, used for experiments in 2014, has been performed. For this purpose we use the Torino Polytechnic Ion Cyclotron Antenna (TOPICA) code and asymptotic version of the Self-consistent Sheaths and Waves for Ion Cyclotron Heating (SSWICH) code. Further, we investigate correlation between amplitudes of the calculated oscillating sheath voltages and the E// fields computed at the lateral side of the antenna box, in relation with a heuristic antenna design strategy at IPP Garching to mitigate RF sheaths.

  1. Initial Operation of the Alcator C-Mod ICRF Antennas with High-Z Metal Antenna Guards

    SciTech Connect

    Schilling, G.; Wukitch, S.J.; Lin, Y.; Parisot, A.; Porkolab, M.

    2005-09-26

    The Alcator C-Mod ICRF antennas have been operated with BN antenna guards since 2000. This modification had followed the observation that metallic impurities in the plasma increased with increasing ICRF power. Systematic improvements to the antenna structure have allowed the launched power to be raised to the 6 MW level, with good heating efficiency and few deleterious effects on the plasma. BN is inherently fragile, and disruption mechanical shocks have resulted in fracturing of the antenna tiles, exposing the supporting metal structure. Since the antennas are now electrically in reasonable shape, and one of C-Mod's goals is to study the behavior of plasmas with all-metal plasma facing components, it was decided to replace the BN tiles with molybdenum. High power operation was resumed in March, 2005, and the behavior of the antennas during the present run campaign will be reported.

  2. Coupling Of The JET ICRF Antennas In ELMy H-mode Plasmas With ITER Relevant Plasma-Straps Distance

    SciTech Connect

    Mayoral, M.-L.; Monakhov, I.; Jacquet, P.; Brix, M.; Graham, M.; Erents, K.; Korotkov, A.; Lomas, P.; Mailloux, J.; McDonald, D. C.; Stamp, M.; Walden, A.; Hobirk, J.; Ongena, J.

    2007-09-28

    In ITER, the requirement for the ICRF antenna is to deliver 20 MW in ELMy H-mode plasmas with an averaged antenna - plasma separatrix distance of 14 cm. Two major problems will have to be solved: the very fast change in antenna loading during ELMs and the decrease of the loading when the plasma is pushed far away from the antenna. JET has the capability to combine these conditions and for the first time, experiments were performed in ELMy H-mode at antenna--separatrix distance, referred as ROG, varied from 10 to 14 cm. When ROG was increased, the perturbation caused by ELMs was found to decrease significantly and the loading between ELMs was found to deteriorate to very low values. In order to compensate the latter unwanted effect, different levels of deuterium gas were injected in the edge either from the divertor, the midplane or the top of the tokamak. Using this technique, the loading was increased by up to a factor 6 and up to 8 MW of ICRF power were coupled.

  3. Effect on the tritium breeding ratio for a distributed ICRF antenna in a DEMO reactor

    NASA Astrophysics Data System (ADS)

    Garcia, A.; Noterdaeme, J.-M.; Fischer, U.; Dies, J.

    2015-12-01

    The paper reports results of MCNP-5 calculations to assess the effect on the Tritium Breeding Ratio (TBR) when integrating a distributed Ion Cyclotron Range of Frequencies (ICRF) antenna in the blanket of DEMO fusion power reactor. The calculations consider different parameters such as the ICRF covering ratio and the type of breeding blanket including the Helium Cooled Pebble Bed (HCPB) and the Helium Cooled Lithium Lead (HCLL) concepts. For an antenna with a full toroidal circumference of 360°, located poloidally at 40° with a poloidal extension of 1 m, the reduction of the TBR is -0.349% for the HCPB blanket and -0.532% for the HCLL blanket. The distributed ICRF antenna is thus shown to have only a marginal effect on the TBR of the DEMO reactor.

  4. Effect on the tritium breeding ratio for a distributed ICRF antenna in a DEMO reactor

    SciTech Connect

    Garcia, A.; Noterdaeme, J.-M.; Fischer, U.; Dies, J.

    2015-12-10

    The paper reports results of MCNP-5 calculations to assess the effect on the Tritium Breeding Ratio (TBR) when integrating a distributed Ion Cyclotron Range of Frequencies (ICRF) antenna in the blanket of DEMO fusion power reactor. The calculations consider different parameters such as the ICRF covering ratio and the type of breeding blanket including the Helium Cooled Pebble Bed (HCPB) and the Helium Cooled Lithium Lead (HCLL) concepts. For an antenna with a full toroidal circumference of 360°, located poloidally at 40° with a poloidal extension of 1 m, the reduction of the TBR is −0.349% for the HCPB blanket and −0.532% for the HCLL blanket. The distributed ICRF antenna is thus shown to have only a marginal effect on the TBR of the DEMO reactor.

  5. A folded waveguide ICRF antenna for PBX-M and TFTR

    SciTech Connect

    Bigelow, T.S.; Carter, M.D.; Fogelman, C.H.

    1995-09-01

    The folded waveguide (FWG) antenna is an advanced ICRF launcher under development at ORNL that offers many significant advantages over current-strap type antennas. These features are particularly beneficial for reactor-relevant applications such as ITER and TPX. Previous tests of a development folded waveguide with a low density plasma load have shown a factor of 5 increase in power capability over loop antennas into similar plasma conditions. The performance and reliability of a FWG with an actual tokamak plasma load must now be verified for further acceptance of this concept. A 58 MHz, 4 MW folded waveguide is being designed and built for the PBX-M and TFTR tokamaks at Princeton Plasma Physics Laboratory. This design has a square cross-section that can be installed as either a fast wave (FW) or ion-Bernstein wave (IBW) launcher by 90{degree} rotation. Two new features of the design are: a shorter quarter-wavelength resonator configuration and a rear-feed input power coupling loop. Loading calculations with a standard shorting plate indicate that a launched power level of 4 MW is possible on either machine. Mechanical and disruption force analysis indicates that bolted construction will withstand the disruption loads. An experimental program is planned to characterize the plasma loading, heating effectiveness, power capability, impurity generation and other factors for both FW and IBW cases. High power tests of the new configuration are being performed with a development FWG unit on RFTF at ORNL.

  6. Reduction of RF sheaths potentials by compensation or suppression of parallel RF currents on ICRF antennae

    NASA Astrophysics Data System (ADS)

    Mendes, A.; Colas, L.; Vulliez, K.; Argouarch, A.; Milanesio, D.

    2009-11-01

    Radio Frequency (RF) sheaths are suspected to limit the performance of present-day Ion Cyclotron Range of Frequencies (ICRF) antennae over long pulses and should be minimized in future Fusion devices. Within the simplest models, RF sheath effects are quantified by the integral VRF = ∫E//ṡdl where the parallel RF field E// is linked with the slow wave. On "long open field lines" with large toroidal extension on both sides of the antenna it was shown that VRF is excited by parallel RF currents j// flowing on the antenna structure. We thus propose two ways to reduce |VRF| by acting on j// on the antenna front face. The first method, more adapted for protruding antennae, consists in avoiding the j// circulation on the antenna structure, by slotting the antenna frame on its horizontal edges and by cutting partially the Faraday screen rods. The second method, well suited for recessed antennae, consists in compensating j// of opposite signs along long flux tubes, with parallelepiped antennae aligned with tilted flux tubes. The different concepts are assessed numerically on a 2-strap Tore Supra antenna phased [0, π] using near RF fields from the antenna code TOPICA. Simulations stress the need to suppress all current paths for j// to reduce substantially |VRF| over the whole antenna height.

  7. Analysis and design of ICRF antennas for cylindrical plasmas with TOPCYL

    NASA Astrophysics Data System (ADS)

    Guadamuz, Saul; Maggiora, Riccardo

    2010-11-01

    On recent years TOPICA[1] has shown its capabilities as a designing and predicting tool for ICRF antennas on tokamaks, handling at the same time realistic geometrical detail of the structure as well as a complete description of the plasma region. Now, expanding these capabilities, the TOrino POlitecnico CYLindrical (TOPCYL) code has been released in order to give a full wave simulation of ICRF antennas in front of cylindrical plasma columns, thus inheriting from TOPICA the geometrical accuracy and keeping the completeness of the specific plasma model. This feature allows the analysis and design of RF heating systems for specific applications as plasma thrusters and plasma-surface-interaction experiments; nevertheless in general the only requirement is for the plasma to be cylindrical. In the present work, the theoretical basis, the implementation and validation of TOPCYL is presented.[4pt] [1] Nucl. Fusion, 46 (2006) S476.

  8. RF-sheath heat flux estimates on Tore Supra and JET ICRF antennae. Extrapolation to ITER

    SciTech Connect

    Colas, L.; Portafaix, C.; Goniche, M.; Jacquet, Ph.

    2009-11-26

    RF-sheath induced heat loads are identified from infrared thermography measurements on Tore Supra ITER-like prototype and JET A2 antennae, and are quantified by fitting thermal calculations. Using a simple scaling law assessed experimentally, the estimated heat fluxes are then extrapolated to the ITER ICRF launcher delivering 20 MW RF power for several plasma scenarios. Parallel heat fluxes up to 6.7 MW/m{sup 2} are expected very locally on ITER antenna front face. The role of edge density on operation is stressed as a trade-off between easy RF coupling and reasonable heat loads. Sources of uncertainty on the results are identified.

  9. Fast ion generation and bulk plasma heating with three-ion ICRF scenarios

    SciTech Connect

    Kazakov, Ye. O. Van Eester, D.; Ongena, J.; Lerche, E.; Messiaen, A.

    2015-12-10

    Launching electromagnetic waves in the ion cyclotron range of frequencies (ICRF) is an efficient method of plasma heating, actively employed in most of fusion machines. ICRF has a number of important supplementary applications, including the generation of high-energy ions. In this paper, we discuss a new set of three-ion ICRF scenarios and the prospect of their use as a dedicated tool for fast ion generation in tokamaks and stellarators. A distinct feature of these scenarios is a strong absorption efficiency possible at very low concentrations of resonant minority ions (∼ 1% or even below). Such concentration levels are typical for impurities contaminating fusion plasmas. An alternative ICRF scenario for maximizing the efficiency of bulk D-T ion heating is suggested for JET and ITER tokamaks, which is based on three-ion ICRF heating of intrinsic Beryllium impurities.

  10. Fast ion generation and bulk plasma heating with three-ion ICRF scenarios

    NASA Astrophysics Data System (ADS)

    Kazakov, Ye. O.; Van Eester, D.; Dumont, R.; Ongena, J.; Lerche, E.; Messiaen, A.

    2015-12-01

    Launching electromagnetic waves in the ion cyclotron range of frequencies (ICRF) is an efficient method of plasma heating, actively employed in most of fusion machines. ICRF has a number of important supplementary applications, including the generation of high-energy ions. In this paper, we discuss a new set of three-ion ICRF scenarios and the prospect of their use as a dedicated tool for fast ion generation in tokamaks and stellarators. A distinct feature of these scenarios is a strong absorption efficiency possible at very low concentrations of resonant minority ions (˜ 1% or even below). Such concentration levels are typical for impurities contaminating fusion plasmas. An alternative ICRF scenario for maximizing the efficiency of bulk D-T ion heating is suggested for JET and ITER tokamaks, which is based on three-ion ICRF heating of intrinsic Beryllium impurities.

  11. ITER ICRF Antenna Reduced-Scale Mock-up EM Simulations and Comparisons with the Measurements

    NASA Astrophysics Data System (ADS)

    Kyrytsya, V.; Dumortier, P.; Messiaen, A.; Louche, F.; Vervier, M.

    2009-11-01

    A reduced-scale mock-up of one ITER ICRF antenna triplet has been recently built, featuring the optimized front-end geometry, an optimized 4-port junction and the implementation of a service stub. Provision is made to adapt the frequency response of the antenna by acting on the 4-port junction arms lengths, the service stub length as well as the position of its inclusion in the circuit. Variable antenna loading is achieved by moving a salted water tank in front of the antenna. A summary of the first measurements carried out on this mockup is reported in a companion paper [1]. The EM simulations of the mock-up are done with CST Microwave Studio®. The geometry of the mock-up is converted from a CAD file and all essential details are included in the model. S parameters of the mock-up are calculated in a large frequency range covering the ITER ICRF antenna frequency band for different geometries of the mock-up and distances to the load. Results of the simulations and systematic comparisons with the measurements are presented.

  12. ITER ICRF Antenna Reduced-Scale Mock-up EM Simulations and Comparisons with the Measurements

    SciTech Connect

    Kyrytsya, V.; Dumortier, P.; Messiaen, A.; Louche, F.; Vervier, M.

    2009-11-26

    A reduced-scale mock-up of one ITER ICRF antenna triplet has been recently built, featuring the optimized front-end geometry, an optimized 4-port junction and the implementation of a service stub. Provision is made to adapt the frequency response of the antenna by acting on the 4-port junction arms lengths, the service stub length as well as the position of its inclusion in the circuit. Variable antenna loading is achieved by moving a salted water tank in front of the antenna. A summary of the first measurements carried out on this mockup is reported in a companion paper. The EM simulations of the mock-up are done with CST Microwave Studio registered. The geometry of the mock-up is converted from a CAD file and all essential details are included in the model. S parameters of the mock-up are calculated in a large frequency range covering the ITER ICRF antenna frequency band for different geometries of the mock-up and distances to the load. Results of the simulations and systematic comparisons with the measurements are presented.

  13. Design of a High Power Prototype for the new JET-EP ICRF antenna

    NASA Astrophysics Data System (ADS)

    Goulding, R. H.; Baity, F. W.; Jones, G. H.; Nelson, B. E.; Rasmussen, D. A.; Swain, D. W.; Hosea, J. C.; Loesser, G. D.; Wilson, J. R.; Durodie, F.; Beaumont, B.; Lamalle, P. U.; Walton, R.

    2001-10-01

    A high power prototype (HPP) of a new ICRF antenna for JET ("JET-EP antenna") is being designed and constructed in a collaborative effort between Oak Ridge National Laboratory, Princeton Plasma Physics Laboratory, and the European Fusion Development Agreement-Joint European Torus. The JET-EP launcher is designed for 8 MW input power ( 9 MW/m^2) at 30-55 MHz. Current straps are arranged in a 4 poloidal by 2 toroidal array, minimizing voltage. A modified resonant double loop (RDL) matching circuit uses internal capacitors, and passively accommodates rapidly changing plasma loads. The HPP, consisting of one antenna quadrant, will be tested at ORNL in vaccum at >= 33kV pk, 920A rms capacitor voltage and current. Innovative features to be tested include the modified RDL circuit, flanges which allow capacitor replacement without antenna removal, a low characteristic impedance vacuum feed line, and integral matching transformer.

  14. Parasitic signals in the receiving band of the Sub-Harmonic Arc Detection system on JET ICRF Antennas

    SciTech Connect

    Jacquet, P.; Blackman, T.; Day, I. E.; Graham, M.; Mayoral, M.-L.; Monakhov, I.; Nightingale, M.; Sharapov, S. E.; Bobkov, V.; Laxaaback, M.

    2011-12-23

    When testing the SHAD system on JET ICRF antennas, parasitic signals in the detection band (5-20MHz) were detected. We have identified emission from grid breakdown events in the Neutral Beam injectors, and Ion Cyclotron Emission from the plasma. Spurious signals in the band 4-10 MHz are also often observed at the onset of ELM events. Such parasitic signals could complicate the design and operation of SHAD in ICRF systems for fusion devices.

  15. Influence of gas injection location and magnetic perturbations on ICRF antenna performance in ASDEX Upgrade

    SciTech Connect

    Bobkov, V.; Bilato, R.; Dux, R.; Faugel, H.; Kallenbach, A.; Müller, H. W.; Potzel, S.; Pütterich, Th.; Suttrop, W.; Stepanov, I.; Noterdaeme, J.-M.; Jacquet, P.; Monakhov, I.; Czarnecka, A.; Collaboration: ASDEX Upgrade Team

    2014-02-12

    In ASDEX Upgrade H-modes with H{sub 98}≈0.95, similar effect of the ICRF antenna loading improvement by local gas injection was observed as previously in L-modes. The antenna loading resistance R{sub a} between and during ELMs can increase by more than 25% after a switch-over from a deuterium rate of 7.5⋅10{sup 21} D/s injected from a toroidally remote location to the same amount of deuterium injected close to an antenna. However, in contrast to L-mode, this effect is small in H-mode when the valve downstream w.r.t. parallel plasma flows is used. In L-mode, a non-linearity of R{sub a} at P{sub ICRP}<30 kW is observed when using the gas valve integrated in antenna. Application of magnetic perturbations (MPs) in H-mode discharges leads to an increase of R{sub a}>30% with no effect of spectrum and phase of MPs on R{sub a} found so far. In the case ELMs are fully mitigated, the antenna loading is higher and steadier. In the case ELMs are not fully mitigated, the value of R{sub a} between ELMs is increased. Looking at the W source modification for the improved loading, the local gas injection is accompanied by decreased values of tungsten (W) influx Γ{sub W} from the limiters and its effective sputtering yield Y{sub w}, with the exception of the locations directly at the antenna gas valve. Application of MPs leads to increase of Γ{sub W} and Y{sub w} for some of the MP phases. With nitrogen seeding in the divertor, ICRF is routinely used to avoid impurity accumulation and that despite enhanced Γ{sub W} and Y{sub W} at the antenna limiters.

  16. Analysis of 4-strap ICRF Antenna Performance in Alcator C-Mod

    SciTech Connect

    G. Schilling; S.J. Wukitch; R.L. Boivin; J.A. Goetz; J.C. Hosea; J.H. Irby; Y. Lin; A. Parisot; M. Porkolab; J.R. Wilson; the Alcator C-Mod Team

    2003-07-31

    A 4-strap ICRF antenna was designed and fabricated for plasma heating and current drive in the Alcator C-Mod tokamak. Initial upgrades were carried out in 2000 and 2001, which eliminated surface arcing between the metallic protection tiles and reduced plasma-wall interactions at the antenna front surface. A boron nitride septum was added at the antenna midplane to intersect electric fields resulting from radio-frequency sheath rectification, which eliminated antenna corner heating at high power levels. The current feeds to the radiating straps were reoriented from an E||B to E parallel B geometry, avoiding the empirically observed {approx}15 kV/cm field limit and raising antenna voltage holding capability. Further modifications were carried out in 2002 and 2003. These included changes to the antenna current strap, the boron nitride tile mounting geometry, and shielding the BN-metal interface from the plasma. The antenna heating efficiency, power, and voltage characteristics under these various configurations will be presented.

  17. Efficient Self Consistent 3D/1D Analysis of ICRF Antennas

    NASA Astrophysics Data System (ADS)

    Maggiora, R.; Vecchi, G.; Lancellotti, V.; Kyrytsya, V.

    2003-12-01

    An innovative tool has been realized for the 3D/1D simulation of Ion Cyclotron Radio Frequency (ICRF), i.e. accounting for antennas in a realistic 3D geometry and with an accurate 1D plasma model. The approach to the problem is based on an integral-equation formulation for the self-consistent evaluation of the current distribution on the conductors. The environment has been subdivided in two coupled region: the plasma region and the vacuum region. The two problems are linked by means of a magnetic current (electric field) distribution on the aperture between the two regions. In the vacuum region all the calculations are executed in the spatial domain while in the plasma region an extraction in the spectral domain and an analytical evaluation of some integrals are employed that permit to significantly reduce the integration support and to obtain a high numerical efficiency leading to the practical possibility of using a large number of sub-domain basis functions on each solid conductor of the system. The plasma enters the formalism of the plasma region via a surface impedance matrix; for this reason any plasma model can be used; at present the FELICE code has been adopted, that affords density and temperature profiles, and FLR effects. The source term directly models the TEM mode of the coax feeding the antenna and the current in the coax is determined self-consistently, giving the input impedance/admittance of the antenna itself. Calculation of field distributions (both magnetic and electric), useful for sheath considerations, is included. This tool has been implemented in a suite, called TOPICA, that is modular and applicable to ICRF antenna structures of arbitrary shape. This new simulation tool can assist during the detailed design phase and for this reason can be considered a "Virtual Prototyping Laboratory" (VPL). The TOPICA suite has been tested against assessed codes and against measurements and data of mock-ups and existing antennas. The VPL is being used

  18. The Tore Supra ITER like ICRF antenna prototype

    SciTech Connect

    Vulliez, K.; Agarici, G.; Argouarch, A.; Beaumont, B.; Becoulet, A.; Berger-by, G.; Bosia, G.; Bremond, S.; Colas, L.; Lombard, G.; Millon, L.; Mollard, P.; Hoang, G. T.; Volpe, D.

    2007-09-28

    In the framework of the ICRH development led at CEA Cadarache, a project of a prototype antenna based on the electrical layout foreseen for the ITER IC launcher has been initiated. First experiments have been performed on Tore Supra in 2004. Pulses of 500 kW lasting up to 6s have been achieved. The importance of the coupling effect between straps has been revealed during these experiments, and thus the need for an active control system of the current phasing between them. Despite the short experimental campaign terminated by the failure of the matching components due to undetected arcs, the load tolerant properties of such a circuit have been observed.Since, the prototype antenna has been repaired, reassembled and enhanced accordingly to the fruitful lessons harvested. The RF circuit was improved, corona rings were added on the capacitor poles and localized 'sharp' edges were rounded to increase the voltage standoff capability. To reduce the toroidal coupling between adjacent straps, a thick poloidal septum was added on the Faraday screen, thus easing the tuning of the launcher. Another major improvement was the development and the integration of current probes on each of the four straps. This paper reports on: the launcher mechanical enhancements, the recent results obtained in 2007 and the experimental program planned on Tore Supra.

  19. Materials tests and analyses of Faraday shield tubes for ICRF antennas

    SciTech Connect

    King, J.F.; Baity, F.W.; Hoffman, D.J.; Walls, J.C.; Taylor, D.J.

    1989-03-01

    The ion cyclotron resonant frequency (ICRF) antennas for heating fusion plasmas require careful analysis of the materials selected for the design and the successful fabrication of high integrity braze bonds. Graphite tiles are brazed to Inconel 625 Faraday shield tubes to protect the antenna from the plasma. The bond between the graphite and Inconel tube is difficult to achieve due to the different coefficients of thermal expansion. A 2-D stress analysis showed the graphite could be bonded to Inconel with a Ag-Cu-Ti braze alloy without cracking the graphite. Brazing procedures and nondestructive examination methods have been developed for these joints. This paper presents the results of their joining development and proof testing.

  20. Materials tests and analyses of Faraday shield tubes for ICRF (ion cyclotron resonant frequency) antennas

    SciTech Connect

    King, J.F.; Baity, F.W.; Hoffman, D.J.; Walls, J.C.; Taylor, D.J.

    1988-01-01

    The ion cyclotron resonant frequency (ICRF) antennas for heating fusion plasmas require careful analysis of the materials selected for the design and the successful fabrication of high integrity braze bonds. Graphite tiles are brazed to Inconel 625 Faraday shield tubes to protect the antenna from the plasma. The bond between the graphite and Inconel tube is difficult to achieve due to the different coefficients of thermal expansion. A 2-D stress analysis showed the graphite could be bonded to Inconel with a Ag-Cu-Ti braze alloy without cracking the graphite. Brazing procedures and nondestructive examination methods have been developed for these joints. This paper presents the results of our joining development and proof testing. 2 refs., 3 figs.

  1. Accurate design of ICRF antennas for RF plasma thruster acceleration units with TOPICA

    NASA Astrophysics Data System (ADS)

    Lancellotti, V.; Maggiora, R.; Vecchi, G.; Milanesio, D.; Meneghini, O.

    2007-09-01

    In recent years electromagnetic (RF) plasma generation and acceleration concepts for plasma-based propulsion systems have received growing interest, inasmuch as they can yield continuous thrust as well as highly controllable and wide-ranging exhaust velocities. The acceleration units mostly adopt the Ion Cyclotron Resonance Frequency (ICRF)—a proven technology in fusion experiments for transferring large RF powers into magnetized plasmas, and also used by the VASIMR propulsion system. In this work we propose and demonstrate the use of TOPICA code to design and optimize the ICRF antenna of a typical acceleration stage. To this end, TOPICA was extended to cope with magnetized cylindricaily-symmetric radially-inhomogeneous warm plasmas, which required coding a new module charged with solving Maxwell's equations within the plasma to obtain the relevant Green's function Ỹ(m,kz) in the Fourier domain, i.e. the relation between the transverse magnetic and electric fields at the air-plasma interface. Then, calculating the antenna input impedance—and hence the loading—relies on an integral-equation formulation and subsequent finite-element weighted-residual solution scheme for the self-consistent evaluation of the current density distribution on the conducting bodies and at the air-plasma interface.

  2. Analysis of large complex ICRF and LH antenna systems by TOPICA

    NASA Astrophysics Data System (ADS)

    Lancellotti, Vito; Milanesio, Daniele; Meneghini, Orso; Maggiora, Riccardo; Kyrytsya, Volodymyr; Vecchi, Giuseppe

    2006-10-01

    Auxiliary ICRF heating systems in tokamaks often involve large complex antennas, made up of several conducting straps hosted in distinct cavities that open towards the plasma. The same holds especially true in the LH regime, wherein the antennas are comprised of arrays of many phased waveguides. Upon observing that the various cavities or waveguides couple to each other only through the EM fields existing over the plasma-facing apertures, we self-consistently formulated the EM problem by a convenient set of multiple coupled integral equations. Subsequent application of the Method of Moments yields a highly sparse algebraic system; therefore formal inversion of the system matrix happens to be not so memory demanding, despite the number of unknowns may be quite large (typically 15000 or so). The overall strategy has been implemented in an enhanced version of TOPICA (Torino Polytechnic Ion Cyclotron Antenna) [1], a simulation and prediction tool for plasma facing antennas that incorporates commercial-grade 3D graphic interfaces along with an accurate description of the plasma. In this work we present the new proposed formulation along with examples of application to real life large ICRH and LH antenna systems. [1] V. Lancellotti et al., Nucl. Fusion, 46 (2006) S476-S499

  3. Upgrades to the 4-strap ICRF antenna in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Schilling, G.; Hosea, J. C.; Wilson, J. R.; Beck, W.; Boivin, R. L.; Bonoli, P. T.; Gwinn, D.; Lee, W. D.; Nelson-Melby, E.; Porkolab, M.; Vieira, R.; Wukitch, S. J.; Goetz, J. A.

    2001-10-01

    A 4-strap ICRF antenna suitable for plasma heating and current drive has been designed and fabricated for the Alcator C-Mod tokamak. Initial operation in plasma was limited by high metallic impurity injection resulting from front surface arcing between protection tiles and from current straps to Faraday shields. Antenna modifications were made in 2/2000, resulting in impurity reduction, but low heating efficiency was observed when the antenna was operated in its 4-strap rather than a 2-strap configuration. Further modifications were made in 7/2000, with the installation of BN plasma-facing tiles and radiofrequency bypassing of the antenna backplane edges and ends to reduce potential leakage coupling to plasma surface modes. Good heating efficiency was now observed in both heating configurations, but coupled power was limited to 2.5 MW in H-mode, 3 MW in L-mode, by plasma-wall interactions. Additional modifications were started in 2/2001 and will be completed by this meeting. All the above upgrades and their effect on antenna performance will be presented.

  4. Upgrades to the 4-strap ICRF Antenna in Alcator C-Mod

    SciTech Connect

    G. Schilling; J.C. Hosea; J.R. Wilson; W. Beck; R.L. Boivin; P.T. Bonoli; D. Gwinn; W.E. Lee; E. Nelson-Melby; M. Porkolab; R. Vieira; S.J. Wukitch; and J.A. Goetz

    2001-06-12

    A 4-strap ICRF antenna suitable for plasma heating and current drive has been designed and fabricated for the Alcator C-Mod tokamak. Initial operation in plasma was limited by high metallic impurity injection resulting from front surface arcing between protection tiles and from current straps to Faraday shields. Antenna modifications were made in February 2000, resulting in impurity reduction, but low-heating efficiency was observed when the antenna was operated in its 4-strap rather than a 2-strap configuration. Further modifications were made in July 2000, with the installation of BN plasma-facing tiles and radio- frequency bypassing of the antenna backplane edges and ends to reduce potential leakage coupling to plasma surface modes. Good heating efficiency was now observed in both heating configurations, but coupled power was limited to 2.5 MW in H-mode, 3 MW in L-mode, by plasma-wall interactions. Additional modifications were started in February 2001 and will be completed by this meeting. All the above upgrades and their effect on antenna performance will be presented.

  5. Modeling of EAST ICRF antenna performance using the full-wave code TORIC

    SciTech Connect

    Edlund, E. M.; Bonoli, P. T.; Porkolab, M.; Wukitch, S. J.

    2015-12-10

    Access to advanced operating regimes in the EAST tokamak will require a combination of electron-cyclotron resonance heating (ECRH), neutral beam injection (NBI) and ion cyclotron range frequency heating (ICRF), with the addition of lower-hybrid current drive (LHCD) for current profile control. Prior experiments at the EAST tokamak facility have shown relatively weak response of the plasma temperature to application of ICRF heating, with typical coupled power about 2 MW out of 12 MW source. The launched spectrum, at n{sub φ} = 34 for 0-π -0-π phasing and 27 MHz, is largely inaccessible at line-averaged densities of approximately 2 × 10{sup 19} m{sup −3}. However, with variable antenna phasing and frequency, this system has considerable latitude to explore different heating schemes. To develop an ICRF actuator control model, we have used the full-wave code TORIC to explore the physics of ICRF wave propagation in EAST. The results presented from this study use a spectrum analysis using a superposition of n{sub φ} spanning −50 to +50. The low density regime typical of EAST plasmas results in a perpendicular wavelength comparable to the minor radius which results in global cavity resonance effects and eigenmode formation when the single-pass absorption is low. This behavior indicates that improved performance can be attained by lowering the peak of the k{sub ||} spectrum by using π/3 phasing of the 4-strap antenna. Based on prior studies conducted at Alcator C-Mod, this phasing is also expected to have the advantage of nearly divergence-free box currents, which should result in reduced levels of impurity production. Significant enhancements of the loading resistance may be achieved by using low k{sub ||} phasing and a combination of magnetic field and frequency to vary the location of the resonance and mode conversion regions. TORIC calculations indicate that the significant power may be channeled to the electrons and deuterium majority. We expect that

  6. Modeling of EAST ICRF antenna performance using the full-wave code TORIC

    NASA Astrophysics Data System (ADS)

    Edlund, E. M.; Bonoli, P. T.; Porkolab, M.; Wukitch, S. J.

    2015-12-01

    Access to advanced operating regimes in the EAST tokamak will require a combination of electron-cyclotron resonance heating (ECRH), neutral beam injection (NBI) and ion cyclotron range frequency heating (ICRF), with the addition of lower-hybrid current drive (LHCD) for current profile control. Prior experiments at the EAST tokamak facility have shown relatively weak response of the plasma temperature to application of ICRF heating, with typical coupled power about 2 MW out of 12 MW source. The launched spectrum, at nφ = 34 for 0-π -0-π phasing and 27 MHz, is largely inaccessible at line-averaged densities of approximately 2 × 1019 m-3. However, with variable antenna phasing and frequency, this system has considerable latitude to explore different heating schemes. To develop an ICRF actuator control model, we have used the full-wave code TORIC to explore the physics of ICRF wave propagation in EAST. The results presented from this study use a spectrum analysis using a superposition of nφ spanning -50 to +50. The low density regime typical of EAST plasmas results in a perpendicular wavelength comparable to the minor radius which results in global cavity resonance effects and eigenmode formation when the single-pass absorption is low. This behavior indicates that improved performance can be attained by lowering the peak of the k|| spectrum by using π/3 phasing of the 4-strap antenna. Based on prior studies conducted at Alcator C-Mod, this phasing is also expected to have the advantage of nearly divergence-free box currents, which should result in reduced levels of impurity production. Significant enhancements of the loading resistance may be achieved by using low k|| phasing and a combination of magnetic field and frequency to vary the location of the resonance and mode conversion regions. TORIC calculations indicate that the significant power may be channeled to the electrons and deuterium majority. We expect that implementation of these recommendations in EAST

  7. TOPICA: an accurate and efficient numerical tool for analysis and design of ICRF antennas

    NASA Astrophysics Data System (ADS)

    Lancellotti, V.; Milanesio, D.; Maggiora, R.; Vecchi, G.; Kyrytsya, V.

    2006-07-01

    The demand for a predictive tool to help in designing ion-cyclotron radio frequency (ICRF) antenna systems for today's fusion experiments has driven the development of codes such as ICANT, RANT3D, and the early development of TOPICA (TOrino Polytechnic Ion Cyclotron Antenna) code. This paper describes the substantive evolution of TOPICA formulation and implementation that presently allow it to handle the actual geometry of ICRF antennas (with curved, solid straps, a general-shape housing, Faraday screen, etc) as well as an accurate plasma description, accounting for density and temperature profiles and finite Larmor radius effects. The antenna is assumed to be housed in a recess-like enclosure. Both goals have been attained by formally separating the problem into two parts: the vacuum region around the antenna and the plasma region inside the toroidal chamber. Field continuity and boundary conditions allow formulating of a set of two coupled integral equations for the unknown equivalent (current) sources; then the equations are reduced to a linear system by a method of moments solution scheme employing 2D finite elements defined over a 3D non-planar surface triangular-cell mesh. In the vacuum region calculations are done in the spatial (configuration) domain, whereas in the plasma region a spectral (wavenumber) representation of fields and currents is adopted, thus permitting a description of the plasma by a surface impedance matrix. Owing to this approach, any plasma model can be used in principle, and at present the FELICE code has been employed. The natural outcomes of TOPICA are the induced currents on the conductors (antenna, housing, etc) and the electric field in front of the plasma, whence the antenna circuit parameters (impedance/scattering matrices), the radiated power and the fields (at locations other than the chamber aperture) are then obtained. An accurate model of the feeding coaxial lines is also included. The theoretical model and its TOPICA

  8. Eigenmode analysis of the ITER ICRF antenna plug and electrical solution to the grounding of the antenna

    SciTech Connect

    Louche, F.; Messiaen, A. M.; Dumortier, P.; Durodie, F.; Koch, R.; Lamalle, P. U.

    2009-11-26

    The excitation of resonant modes in the gap between the ITER ICRH antenna plug and the vessel can considerably increase the level of RF currents and voltages on the ITER plug and disturb the radiation characteristic of the array. We report on a study of these modes and a solution to avoid them in the ITER ion cyclotron range of frequencies. From a transmission line approach we show that resonances can be avoided if the distance between the mouth of the line and an added short-circuit is sufficiently small. We therefore propose to position short-circuits at about lm from the antenna mouth, constituted by rows of closely spaced contacts all around the plug. These conclusions are further validated with Microwave Studio simulations. A simplified model of the ITER ICRF array is used for comparing various grounding solutions and it is proved that the solution already inferred from transmission line approximation suppresses the resonances from the frequency domain relevant for ICRH in ITER. The MWS calculations predict that the proposed solution also avoids large RF currents in the blanket modules and in their connectors. Their amplitude barely exceeds 5% of the strap RF currents. This solution avoids perturbation of the antenna array impedance matrix by the coaxial gap.

  9. Modeling the ITER ICRF Antenna with Integrated Time Domain RF Sheath and Plasma Physics

    NASA Astrophysics Data System (ADS)

    Smithe, David; D'Ippolito, Daniel; Myra, James; CSWPI Collaboration

    2014-10-01

    We present results from computer simulations of detailed 3D models of the ICRF launcher assembly, including straps, Faraday Shields, and vessel wall. These simulations provide exquisite detail of the antenna near fields, and the sheaths between plasma and the metallic components of the launcher. Significant work has been done to create a sheath model that allows us to estimate local values of sheath potential everywhere on the 3D structure, so that we can estimate RF rectified plasma potential. Those potentials are in turn a likely source of sputtering and impurity creation, when the antennas are operating, and we discuss ongoing work to quantify these effects. Additional study of the antenna near fields also investigates slow waves which can exist in the low density scrape-off layer, and may impact power balance, and also sheath amplitudes. Movies of the 3D field and sheath oscillations will be shown. Supported by DOE Grants DE-08ER54953 and DE-FG02-09ER55006.

  10. Initial Testing of Optical Arc Detector Inside 285/300 Fast Wave Antenna Box on DIII-D

    SciTech Connect

    Diem, Stephanie J; Fehling, Dan T; Hillis, Donald Lee; Horton, Anthony R; Unterberg, E. A.; Nagy, A.; Pinsker, R.

    2013-01-01

    Locating arcs within the fast wave current drive system is necessary to improve antenna performance and coupling to the plasma. Previously, there had been no way to observe arcs inside the vacuum vessel in an ICRF antenna on DIII-D. A new diagnostic that uses photomultiplier tubes has been installed for the 2012 run campaign on the 285/300 antenna of the fast wave system. The diagnostic has top and bottom views of the back of the four antenna straps and uses narrow-bandpass visible filters to isolate emission lines of copper (577 nm) and deuterium (656.1 nm). This diagnostic is based on the ORNL filterscope system currently in use on multiple devices. The system will be used to guide fast wave antenna conditioning, plasma operation and provide insight into future antenna upgrades on DIII-D.

  11. Validation of a 3D/1D Simulation Tool for ICRF Antennas

    NASA Astrophysics Data System (ADS)

    Maggiora, R.; Lancellotti, V.; Milanesio, D.; Vecchi, G.; Kyrytsya, V.; Parisot, A.; Wukitch, S. J.

    2005-09-01

    TOPICA is an innovative tool for the simulation of the Ion Cyclotron Radio Frequency (ICRF) antenna systems that incorporates commercial-grade graphic interfaces into a fully 3D self-consistent description of the antenna geometry and an accurate description of the plasma; it can be considered as a "Virtual Prototyping Laboratory" to assist the detailed design phase of the antenna system. Recent theoretical and computational advances of the TOPICA code has allowed to incorporate a CAD drawing capability of the antenna geometry, with fully 3D geometrical modeling, and to combine it with a 1D accurate plasma description that takes into account density and temperature profiles, and FLR effects; the profiles are inserted directly from measured data (when available), or specified analytically by the user. The coaxial feeding line is modeled as such; computation and visualization of relevant parameters (input scattering parameters, current and field distributions, etc.) complete the suite. The approach to the problem is based on an integral-equation formulation for the self-consistent evaluation of the current distribution on the conductors. The environment has been subdivided in two coupled region: the plasma region and the vacuum region. The two problems are linked self-consistently by representing the field continuity in terms of equivalent (unknown) sources. In the vacuum region all the calculations are executed in the spatial (configuration) domain, and this allows triangular-facet description of the arbitrarily shaped conductors and associated currents; in the plasma region a spectral representation of the fields is used, which allows to enter the plasma effect via a surface impedance matrix; for this reason any plasma model can be used, and at present the FELICE code has been adopted; special techniques have been adopted to increase the numerical efficiency. The TOPICA suite has been previously tested against assessed codes and against measurements of mock-ups and

  12. Validation of the Electrical Properties of the ITER ICRF Antenna using Reduced-Scale Mock-Ups

    SciTech Connect

    Dumortier, Pierre; Durodie, Frederic; Grine, Djamel; Kyrytsya, Volodymyr; Louche, Fabrice; Messiaen, Andre; Vervier, Michel; Vrancken, Mark

    2011-12-23

    Experimental measurements on reduced-scale mock-ups allow validating the electrical properties and RF numerical optimization of the ITER ICRF antenna. Frequency response in the different regions of the antenna is described and key parameters for performance improvement are given. Coupling is improved by acting on the front-face geometry (strap width, antenna box depth and vertical septa recess). The 4-port junction acts as a frequency filter and together with the service stub performs pre-matching in the whole frequency band. Influence of the Faraday screen on coupling is limited. The effect of voltage limitation on the maximum total radiated power is given. The importance of a good decoupling network and of grounding is emphasized. Finally the control of the antenna wave spectrum is performed by implementing feedback controlled load-resilient matching and decoupling options and control algorithms are tested.

  13. Interaction of ICRF Fields with the Plasma Boundary in AUG and JET and Guidelines for Antenna Optimization

    NASA Astrophysics Data System (ADS)

    Bobkov, V.; Bilato, R.; Braun, F.; Colas, L.; Dux, R.; Van Eester, D.; Giannone, L.; Goniche, M.; Herrmann, A.; Jacquet, P.; Kallenbach, A.; Krivska, A.; Lerche, E.; Mayoral, M.-L.; Milanesio, D.; Monakhov, I.; Müller, H. W.; Neu, R.; Noterdaeme, J.-M.; Pütterich, Th.; Rohde, V.

    2009-11-01

    W sputtering during ICRF on ASDEX Upgrade (AUG) and temperature rise on JET A2 antenna septa are considered in connection with plasma conditions at the antenna plasma facing components and E‖ near-fields. Large antenna-plasma clearance, high gas puff and low light impurity content are favorable to reduce W sputtering in AUG. The spatial distribution of spectroscopically measured effective W sputtering yields clearly points to the existence of strong E‖ fields at the antenna box ("feeder fields") which dominate over the fields in front of the antenna straps. The picture of E‖ fields, obtained by HFSS code, corroborates the dominant role of E‖ at the antenna box on the formation of sheath-driving RF voltages for AUG. Large antenna-plasma clearance and low gas puff are favorable to reduce septum temperature of JET A2 antennas. Assuming a linear relation between the septum temperature and the sheath driving RF voltage calculated by HFSS, the changes of the temperature with dipole phasing (00ππ, 0ππ0 or 0π0π) are well described by the related changes of the RF voltages. Similarly to the AUG antenna, the strongest E‖ are found at the limiters of the JET A2 antenna for all used dipole phasings and at the septum for the phasings different from 0π0π. A simple general rule can be used to minimize E‖ at the antenna: image currents can be allowed only at the surfaces which do not intersect magnetic field lines at large angles of incidence. Possible antenna modifications generally rely either on a reduction of the image currents, on their short-circuiting by introducing additional conducting surfaces or on imposing the E‖ = 0 boundary condition. On the example of AUG antenna, possible options to minimize the sheath driving voltages are presented.

  14. Performance of the ITER ICRF Antenna plug as expected from TOPICA matrices

    NASA Astrophysics Data System (ADS)

    Messiaen, A.; Koch, R.; Dumortier, P.; Louche, F.; Maggiora, R.; Milanesio, D.; Weynants, R.

    2009-11-01

    The performances of the present ICRF antenna plug design is evaluated by means of the TOPICA 24×24 matrix for plasma loading supplemented by 4-port junction (4PJ) matrices. For their interpretation these results are compared with a cruder modeling by the semi-analytical code ANTITER II. From this analysis we conclude: (1) The broadbanding effect of the service stub on the response of the 4PJ made for one triplet is maintained for the complete array for all the heating and current drive phasings. (2) For a given maximum voltage of the 8 feeding lines the radiated power capability is roughly constant in the entire frequency band. (3) The power capability of the array is significantly dependent on the distance of the antenna to the Last Closed Flux Surface, the density profile in the scrape-off layer (SOL) and on the toroidal and poloidal phasings. The dependence on phasing is stronger for wider SOL (4) For a not too optimistic plasma density profile (Sc2 shortl7) a power capability exceeding 20 MW is only obtained for the 00 ππ heating toroidal phasing and for the co-current drive phasing in the upper part of the frequency band for a maximum voltage in the complete system of 45 kV. (5), On account of the plasma gyrotropy the quadrature poloidal phasing introduced by hybrid feeding must excite waves propagating upwards in the ITER configuration to obtain the best coupling, (6) The large power capability difference between opposite current drive phasings is attributed to the coupling between the toroidal and poloidal phasings induced by the poloidal steady magnetic field.

  15. Preparing ITER ICRF: development and analysis of the load resilient matching systems based on antenna mock-up measurements

    NASA Astrophysics Data System (ADS)

    Messiaen, A.; Vervier, M.; Dumortier, P.; Grine, D.; Lamalle, P. U.; Durodié, F.; Koch, R.; Louche, F.; Weynants, R.

    2009-05-01

    The reference design for the ICRF antenna of ITER is constituted by a tight array of 24 straps grouped in eight triplets. The matching network must be load resilient for operation in ELMy discharges and must have antenna spectrum control for heating or current drive operation. The load resilience is based on the use of either hybrid couplers or conjugate-T circuits. However, the mutual coupling between the triplets at the low expected loading strongly counteracts the load resilience and the spectrum control. Using a mock-up of the ITER antenna array with adjustable water load matching solutions are designed. These solutions are derived from transmission line modelling based on the measured scattering matrix and are finally tested. We show that the array current spectrum can be controlled by the anti-node voltage distribution and that suitable decoupler circuits can not only neutralize the adverse mutual coupling effects but also monitor this anti-node voltage distribution. A matching solution using four 3 dB hybrids and the antenna current spectrum feedback control by the decouplers provides outstanding performance if each pair of poloidal triplets undergoes a same load variation. Finally, it is verified by modelling that this matching scenario has the same antenna spectrum and load resilience performances as the antenna array loaded by plasma as described by the TOPICA simulation. This is true for any phasing and frequency in the ITER frequency band. The conjugate-T solution is presently considered as a back-up option.

  16. Reduction of RF-sheaths potentials by compensation or suppression of parallel RF currents on ICRF antennas

    NASA Astrophysics Data System (ADS)

    Mendes, A.; Colas, L.; Vulliez, K.; Ekedahl, A.; Argouarch, A.; Milanesio, D.

    2010-02-01

    Radio frequency (RF) sheaths are suspected of limiting the performance of present-day ion cyclotron range of frequencies (ICRFs) antennas over long pulses and should be minimized in future fusion devices. Within the simplest models, RF-sheath effects are quantified by the integral VRF = ∫ Epar · dl where the parallel RF field Epar is linked with the slow wave. On 'long open field lines' with large toroidal extension on both sides of the antenna it was shown that VRF is excited by parallel RF currents jpar flowing on the antenna structure. In this paper, the validity of this simple sheath theory is tested experimentally on the Tore Supra (TS) ITER-like antenna prototype (ILP), together with antenna simulation and post-processing codes developed to compute VRF. The predicted poloidal localization of high-|VRF| zones is confronted to that inferred from experimental data analysis. Surface temperature distribution on ILP front face, as well as ILP-induced modifications of RF coupling and hot spots on a magnetically connected lower hybrid current drive antenna, indicates local maxima of dc plasma potential in both the upper and lower parts of the ILP. This result, qualitatively conforming to VRF simulations, is interpreted in terms of jpar flowing on ILP frame. Once the validation is done, such reliable theoretical models and numerical codes are then employed to provide predictive results. Indeed, we propose two ways to reduce |VRF| by acting on jpar on the antenna front face. The first method, more adapted for protruding antennas, consists of avoiding the jpar circulation on the antenna structure, by slotting the antenna frame on its horizontal edges and by partially cutting the Faraday screen rods. The second method, well suited for recessed antennas, consists of compensating jpar of opposite signs along long flux tubes, with parallelepiped antennas aligned with (tilted) flux tubes. The different concepts are assessed numerically on a two-strap TS antenna phased [0

  17. ICRF antenna and feedthrough development at the Oak Ridge National Laboratory

    NASA Astrophysics Data System (ADS)

    Owens, T. L.; Baity, F. W.; Hoffman, D. J.

    1985-07-01

    Antennas, vacuum feedthroughs, Faraday shields, and antenna materials for application in the ICR frequencies have been analysed and tested. The emphasis on the RDL (resonant double loop) antenna.(AIP)

  18. Brazing of ceramic and graphite to metal in the fabrication of ICRF (ion cyclotron range of frequencies) antenna and feedthrough components

    SciTech Connect

    Schechter, D.E.; Sluss, F.; Hoffman, D.J.

    1987-01-01

    Fabrication of some of the more critical components of ion cyclotron range of frequencies (ICRF) antenna and feedthrough assemblies has involved the brazing of alumina ceramic and graphite to various metals. Copper end pieces have been successfully brazed to alumina cylinders for use in feedthroughs for TEXTOR and in feedthroughs and capacitors for a Tokamak Fusion Test Reactor (TFTR) antenna. Copper-plated Inconel rods and tubes have been armored with graphite for construction of Faraday shields on antennas for Doublet III-D and TFTR. Details of brazing procedures and test results, including rf performance, mechanical strength, and thermal capabilities, are presented. 14 figs.

  19. Quantitative modeling of ICRF antennas with integrated time domain RF sheath and plasma physics

    NASA Astrophysics Data System (ADS)

    Smithe, David N.; D'Ippolito, Daniel A.; Myra, James R.

    2014-02-01

    Significant efforts have been made to quantitatively benchmark the sheath sub-grid model used in our time-domain simulations of plasma-immersed antenna near fields, which includes highly detailed three-dimensional geometry, the presence of the slow wave, and the non-linear evolution of the sheath potential. We present both our quantitative benchmarking strategy, and results for the ITER antenna configuration, including detailed maps of electric field, and sheath potential along the entire antenna structure. Our method is based upon a time-domain linear plasma model [1], using the finite-difference electromagnetic Vorpal/Vsim software [2]. This model has been augmented with a non-linear rf-sheath sub-grid model [3], which provides a self-consistent boundary condition for plasma current where it exists in proximity to metallic surfaces. Very early, this algorithm was designed and demonstrated to work on very complicated three-dimensional geometry, derived from CAD or other complex description of actual hardware, including ITER antennas. Initial work with the simulation model has also provided a confirmation of the existence of propagating slow waves [4] in the low density edge region, which can significantly impact the strength of the rf-sheath potential, which is thought to contribute to impurity generation. Our sheath algorithm is based upon per-point lumped-circuit parameters for which we have estimates and general understanding, but which allow for some tuning and fitting. We are now engaged in a careful benchmarking of the algorithm against known analytic models and existing computational techniques [5] to insure that the predictions of rf-sheath voltage are quantitatively consistent and believable, especially where slow waves share in the field with the fast wave. Currently in progress, an addition to the plasma force response accounting for the sheath potential, should enable the modeling of sheath plasma waves, a predicted additional root to the dispersion

  20. Quantitative modeling of ICRF antennas with integrated time domain RF sheath and plasma physics

    SciTech Connect

    Smithe, David N.; D'Ippolito, Daniel A.; Myra, James R.

    2014-02-12

    Significant efforts have been made to quantitatively benchmark the sheath sub-grid model used in our time-domain simulations of plasma-immersed antenna near fields, which includes highly detailed three-dimensional geometry, the presence of the slow wave, and the non-linear evolution of the sheath potential. We present both our quantitative benchmarking strategy, and results for the ITER antenna configuration, including detailed maps of electric field, and sheath potential along the entire antenna structure. Our method is based upon a time-domain linear plasma model, using the finite-difference electromagnetic Vorpal/Vsim software. This model has been augmented with a non-linear rf-sheath sub-grid model, which provides a self-consistent boundary condition for plasma current where it exists in proximity to metallic surfaces. Very early, this algorithm was designed and demonstrated to work on very complicated three-dimensional geometry, derived from CAD or other complex description of actual hardware, including ITER antennas. Initial work with the simulation model has also provided a confirmation of the existence of propagating slow waves in the low density edge region, which can significantly impact the strength of the rf-sheath potential, which is thought to contribute to impurity generation. Our sheath algorithm is based upon per-point lumped-circuit parameters for which we have estimates and general understanding, but which allow for some tuning and fitting. We are now engaged in a careful benchmarking of the algorithm against known analytic models and existing computational techniques to insure that the predictions of rf-sheath voltage are quantitatively consistent and believable, especially where slow waves share in the field with the fast wave. Currently in progress, an addition to the plasma force response accounting for the sheath potential, should enable the modeling of sheath plasma waves, a predicted additional root to the dispersion, existing at the

  1. Measurement of fast minority /sub 3/He/sup + +/ energy distribution during ICRF heating

    DOEpatents

    Post, D.E. Jr.; Grisham, L.R.; Medley, S.S.

    A method and means for measuring the fast /sub 3/He/sup + +/ distribution during /sub 3/He/sup + +/ minority Ion Cyclotron Resonance Frequency (ICRF) heating is disclosed. The present invention involves the use of 10 to 100 keV beams of neutral helium atoms to neutralize the fast /sub 3/He/sup + +/ ions in a heated plasma by double charge exchange (/sub 3/He/sup + +/ + /sub 4/He/sup 0/ ..-->.. /sub 3/He/sup 0/ + /sub 4/He/sup + +/). The neutralized fast /sub 3/He/sup 0/ atoms then escape from the hot plasma confined by a magnetic field and are detected by conventional neutral particle analyzing means. This technique permits the effectiveness of the coupling of the ion cyclotron waves to the /sub 3/He/sup + +/ minority ions to be accurately measured. The present invention is particularly adapted for use in evaluating the effectiveness of the intermediate coupling between the RF heating and the /sub 3/He/sup + +/ in an energetic toroidal plasma.

  2. 2D modeling of DC potential structures induced by RF sheaths with transverse currents in front of ICRF antenna

    SciTech Connect

    Faudot, E.; Heuraux, S.; Colas, L.

    2005-09-26

    Understanding DC potential generation in front of ICRF antennas is crucial for long pulse high RF power systems. DC potentials are produced by sheath rectification of these RF potentials. To reach this goal, near RF parallel electric fields have to be computed in 3D and integrated along open magnetic field lines to yield a 2D RF potential map in a transverse plane. DC potentials are produced by sheath rectification of these RF potentials. As RF potentials are spatially inhomogeneous, transverse polarization currents are created, modifying RF and DC maps. Such modifications are quantified on a 'test map' having initially a Gaussian shape and assuming that the map remains Gaussian near its summit,the time behavior of the peak can be estimated analytically in presence of polarization current as a function of its width r0 and amplitude {phi}0 (normalized to a characteristic length for transverse transport and to the local temperature). A 'peaking factor' is built from the DC peak potential normalized to {phi}0, and validated with a 2D fluid code and a 2D PIC code (XOOPIC). In an unexpected way transverse currents can increase this factor. Realistic situations of a Tore Supra antenna are also studied, with self-consistent near fields provided by ICANT code. Basic processes will be detailed and an evaluation of the 'peaking factor' for ITER will be presented for a given configuration.

  3. ICRF-enhanced plasma potentials in the SOL of Alcator C-Mod

    SciTech Connect

    Ochoukov, R.; Whyte, D. G.; Brunner, D.; LaBombard, B.; Lipschultz, B.; Terry, J. L.; Wukitch, S. J.; D'Ippolito, D. A.; Myra, J. R.

    2014-02-12

    We performed an extensive survey of the plasma potential in the scrape-off layer (SOL) of Ion Cyclotron Range-of Frequencies (ICRF)-heated discharges on Alcator C-Mod. Our results show that plasma potentials are enhanced in the presence of ICRF power and plasma potential values of >100 V are often observed. Such potentials are high enough to induce sputtering of high-Z molybdenum (Mo) plasma facing components by deuterium ions on C-Mod. For comparison, the plasma potential in Ohmic discharges is typically less than 10 V, well below the threshold needed to induce Mo sputtering by deuterium ions. ICRF-enhanced plasma potentials are observed in the SOL regions that both magnetically map and do not map to active ICRF antennas. Regions that magnetically map to active ICRF antennas are accessible to slow waves directly launched by the antennas and these regions experience plasma potential enhancement that is partially consistent with the slow wave rectification mechanism. One of the most defining features of the slow wave rectification is a threshold appearance of significant plasma potentials (>100 V) when the dimensionless rectification parameter Λ{sub −o} is above unity and this trend is observed experimentally. We also observe ICRF-enhanced plasma potentials >100 V in regions that do not magnetically map to the active antennas and, hence, are not accessible for slow waves launched directly by the active antennas. However, unabsorbed fast waves can reach these regions. The general trend that we observe in these 'un-mapped' regions is that the plasma potential scales with the strength of the local RF wave fields with the fast wave polarization and the highest plasma potentials are observed in discharges with the highest levels of unabsorbed ICRF power. Similarly, we find that core Mo levels scale with the level of unabsorbed ICRF power suggesting a link between plasma potentials in the SOL and the strength of the impurity source.

  4. Measurement of rf voltages on the plasma-touching surfaces of ICRF antennas

    SciTech Connect

    Hoffman, D.J.; Baity, F.W.; Bell, G.L.; Bigelow, T.S.; Caughman, J.B.O.; Goulding, R.H.; Haste, G.R.; Ryan, P.M.; Zhang, H.

    1995-09-01

    Measurements of the rf voltages on Faraday shields and protection bumpers have been made for several loop antennas, including the mock-up antenna and Al for JET, the original antenna for Tore Supra, the present ASDEX-U antenna, and the folded waveguide. The loop antennas show voltages that scale to {approx}12 kV for a maximum input voltage of 30 kV with 0/0 phasing. The voltages are dramatically reduced for 0/{pi} phasing. These voltages are significant in that they can substantially increase the rf sheath potential beyond the levels associated with the simple electromagnetic field linkage from the current straps that results in plasma heating. In this paper, we investigate and measure the source of these voltages, their scaling with antenna impedance, and the differences between the loop arrays.

  5. Measurement of rf voltages on the plasma-touching surfaces of ICRF antennas

    SciTech Connect

    Hoffman, D.J.; Baity, F.W.; Bell, G.L.; Bigelow, T.S.; Caughman, J.B.; Goulding, R.H.; Haste, G.R.; Ryan, P.M.; Zhang, H.

    1996-02-01

    Measurements of the rf voltages on Faraday shields and protection bumpers have been made for several loop antennas, including the mock-up antenna and A1 for JET, the original antenna for Tore Supra, the present ASDEX-U antenna, and the folded waveguide. The loop antennas show voltages that scale to {approx_equal}12 kV for a maximum input voltage of 30 kV with 0/0 phasing. The voltages are dramatically reduced for 0/{pi} phasing. These voltages are significant in that they can substantially increase the rf sheath potential beyond the levels associated with the simple electromagnetic field linkage from the current straps that results in plasma heating. In this paper, we investigate and measure the source of these voltages, their scaling with antenna impedance, and the differences between the loop arrays. {copyright} {ital 1996 American Institute of Physics.}

  6. Measurement of rf voltages on the plasma-touching surfaces of ICRF antennas

    NASA Astrophysics Data System (ADS)

    Hoffman, D. J.; Baity, F. W.; Bell, G. L.; Bigelow, T. S.; Caughman, J. B. O.; Goulding, R. H.; Haste, G. R.; Ryan, P. M.; Zhang, H.

    1996-02-01

    Measurements of the rf voltages on Faraday shields and protection bumpers have been made for several loop antennas, including the mock-up antenna and A1 for JET, the original antenna for Tore Supra, the present ASDEX-U antenna, and the folded waveguide. The loop antennas show voltages that scale to ≊12 kV for a maximum input voltage of 30 kV with 0/0 phasing. The voltages are dramatically reduced for 0/π phasing. These voltages are significant in that they can substantially increase the rf sheath potential beyond the levels associated with the simple electromagnetic field linkage from the current straps that results in plasma heating. In this paper, we investigate and measure the source of these voltages, their scaling with antenna impedance, and the differences between the loop arrays.

  7. Radial Broadening of DC potential structures in front of ICRF antennas by transverse exchange of RF currents

    SciTech Connect

    Faudot, E.; Heuraux, S.; Colas, L.; Gunn, J.

    2009-11-26

    Measurements show that the vicinity of powered Ion Cyclotron Range of Frequency (ICRF) antennae is biased positively with respect to its environment. This is attributed to RF-sheaths. The radial penetration of DC potentials into Tokamak SOL determines the power deposition on the walls and especially on the antenna structure, which is a key point for long time clean discharges. Within independent flux tube models of RF-sheath rectification the radial penetration of DC potentials is determined by the skin depth x{sub 0} = c/{omega}{sub pe} for the slow wave. When self-consistent exchanges of transverse RF currents are allowed between neighboring flux tubes, such a structure can be broadened radially up to a characteristic transverse length L. Broadening arises as soon as L>r{sub 0}. A linear modeling gives a first evaluation of the theoretical length L{approx_equal}(L{sub parallel} {rho}{sub ci}/){sup 1/2}. Within the 'flute assumption' it scales with the length L{sub parallel} of open flux tubes and the ion Larmor radius {rho}{sub ci}. This has been confirmed by the SEM code which takes into account non-linear rectifications. Applying our model to several potential maps generated by an ITER antenna, it comes out that L ranges between 1 and 10 cm depending on local L{sub parallel} and on typical ITER plasma parameters. Langmuir probe measurements on Tore Supra suggest that the broadening is lower than predicted by the code, which supposes that currents do not occur all over the parallel magnetic lines but on a fraction of it.

  8. Simulations of ICRF antenna near-fields in dielectric media and cold plasmas with COMSOL

    NASA Astrophysics Data System (ADS)

    Crombe, K.; Kyrytsya, V.; Koch, R.; Van Eester, D.

    2011-12-01

    Simulations of realistic RF antennas have been performed with the finite element analysis software package COMSOL both with dielectric media and cold plasma loading. Results are presented from simulations with a finite (low) plasma density in the antenna box and ITER like density profile in front of the antenna. First steps were made to introduce the presence of sheaths by means of a non-linear boundary condition. Output characteristics such as scattering parameters and fields have been compared with results from CST Microwave Studio® and the TOPICA code. Good agreement has been found, which illustrates the potential of the present COMSOL-based modeling to benchmark antenna codes. Furthermore non-linear conditions can be imposed on boundaries, which is important for sheath effect modeling.

  9. Fast Approximate Analysis Of Modified Antenna Structure

    NASA Technical Reports Server (NTRS)

    Levy, Roy

    1991-01-01

    Abbreviated algorithms developed for fast approximate analysis of effects of modifications in supporting structures upon root-mean-square (rms) path-length errors of paraboloidal-dish antennas. Involves combination of methods of structural-modification reanalysis with new extensions of correlation analysis to obtain revised rms path-length error. Full finite-element analysis, usually requires computer of substantial capacity, necessary only to obtain responses of unmodified structure to known external loads and to selected self-equilibrating "indicator" loads. Responses used in shortcut calculations, which, although theoretically "exact", simple enough to be performed on hand-held calculator. Useful in design, design-sensitivity analysis, and parametric studies.

  10. 3D electromagnetic optimization of the front face of the ITER ICRF antenna

    NASA Astrophysics Data System (ADS)

    Louche, F.; Dumortier, P.; Messiaen, A.; Durodié, F.

    2011-10-01

    In the framework of the ion cyclotron resonance heating (ICRH) antenna development for ITER, a design based on an external matching concept has been proposed [1]. We present in this work a series of electromagnetic simulations of this design performed with the commercial code CST Microwave Studio [2]. On the one hand, we explore how various geometrical modifications of some parts of the antenna (the straps and the four-port junction) can practically double the RF power coupled to the plasma. This optimization is supported by transmission line analysis. On the other hand, we treat the important question of the opportunity to tilt the straps in the toroidal direction to follow the plasma curvature as close as possible. We show that a configuration with two toroidal segments is sufficient and that further segmentation is not necessary. This work also underlines significant progress in the realism of ICRH antenna modelling and the importance of considering realistic load shaping in the models.

  11. Three-Dimensional Electromagnetic Modeling of the ITER ICRF Antenna (External Matching Design)

    SciTech Connect

    Louche, F.; Lamalle, P.U.; Dumortier, P.; Messiaen, A.M.

    2005-09-26

    The present work reports on 3D radio-frequency (RF) analysis of a design for the ITER antenna with the CST Microwave Studio registered software. The four-port junctions which connect the straps in triplets have been analyzed. Non-TEM effects do not play any significant role in the relevant frequency domain, and a well-balanced splitting of current between the straps inside a triplet is achieved. The scattering matrix has also been compared with RF measurements on a scaled antenna mockup, and the agreement is very good. Electric field patterns along the system have been obtained, and the RF optimization of the feeding sections is under way.

  12. Coupling and matching study of the ICRF antenna for W7-X

    NASA Astrophysics Data System (ADS)

    Messiaen, A.; Krivska, A.; Louche, F.; Ongena, J.; Dumortier, P.; Durodie, F.; Van Eester, D.; Vervier, M.

    2014-02-01

    A tight antenna plug consisting in a pair of straps with strong pre-matching covers the first selected frequency band (25-38MHz) for W7-X and provides the toroidal phasings for heating, current drive and wall conditioning. Another plug-in with two short strap triplets is devoted for operation around 76MHz. The antenna coupling to a reference plasma profile is first analyzed by means of the coupling code ANTITER II. It shows the radiation power spectra for the different phasing cases and indicates the problem of the edge power deposition through the Alfven resonance occurring when the operating frequency is lower than the majority cyclotron frequency. Matrices provided by the TOPICA code are used for the matching-decoupling study of the first antenna plug. The large mutual coupling between the 2 straps is counterbalanced by the use of a decoupler. Finally the tunable 5-port junction used to feed in parallel each triplet of the second plug-in is analyzed by means of MWS simulation together with its decoupling-matching system.

  13. Three-dimensional calculations of fields and loading for loop and folded waveguide ICRF antennas

    NASA Astrophysics Data System (ADS)

    Carter, M. D.; Baity, F. W.; Batchelor, D. B.; Hoffman, D. J.; Jaeger, E. F.; Swain, D. W.; Haste, G. R.

    The ANT and ORION codes have been combined and used to study the loading of various antenna geometries with simple three-dimensional (3-D) effects. Both codes use a slab model with periodic Fourier analysis for modeling the toroidal and poloidal directions. The ANT code is used to prescribe current sets in a vacuum region where the field solutions are obtained analytically of each Fourier mode and matching conditions are used at poloidal/toroidal current sheet locations. Multiple current sheets are permitted and various feeder options are available to model the radial antenna currents. Current elements may be oriented at arbitrary angles to the static magnetic field and may be independently phased in time. The fields at the plasma surface are prescribed by an impedance matrix for each Fourier mode. The ORION code solves for the fields in the plasma region using finite difference techniques, a plasma dispersion relation that retains the lowest-order finite gyroradius effects, and all three electric field components. Results are presented for a folded waveguide mock-up and for a loop antenna design under identical plasma conditions.

  14. Three-dimensional calculations of fields and loading for loop and folded waveguide ICRF antennas

    SciTech Connect

    Carter, M.D.; Baity, F.W.; Batchelor, D.B.; Hoffman, D.J.; Jaeger, E.F.; Swain, D.W.; Haste, G.R.

    1991-01-01

    The ANT and ORION codes have been combined and used to study the loading of various antenna geometries with simple three-dimensional (3-D) effects. Both codes use a slab model with periodic Fourier analysis for modeling the toroidal and poloidal directions. The ANT code is used to prescribe current sets in a vacuum region where the field solutions are obtained analytically of each Fourier mode and matching conditions are used at poloidal/toroidal current sheet locations. Multiple current sheets are permitted and various feeder options are available to model the radial antenna currents. Current elements maybe oriented at arbitrary angles to the static magnetic field and may be independently phased in time. The fields at the plasma surface are prescribed by an impedance matrix for each Fourier mode. The ORION code solves for the fields in the plasma region using finite difference techniques, a plasma dispersion relation that retains the lowest-order finite gyroradius effects, and all three electric field components. Results are presented for a folded waveguide mock-up and for a loop antenna design under identical plasma conditions.

  15. Coupling and matching study of the ICRF antenna for W7-X

    SciTech Connect

    Messiaen, A.; Krivska, A.; Louche, F.; Ongena, J.; Dumortier, P.; Durodie, F.; Van Eester, D.; Vervier, M.

    2014-02-12

    A tight antenna plug consisting in a pair of straps with strong pre-matching covers the first selected frequency band (25-38MHz) for W7-X and provides the toroidal phasings for heating, current drive and wall conditioning. Another plug-in with two short strap triplets is devoted for operation around 76MHz. The antenna coupling to a reference plasma profile is first analyzed by means of the coupling code ANTITER II. It shows the radiation power spectra for the different phasing cases and indicates the problem of the edge power deposition through the Alfven resonance occurring when the operating frequency is lower than the majority cyclotron frequency. Matrices provided by the TOPICA code are used for the matching-decoupling study of the first antenna plug. The large mutual coupling between the 2 straps is counterbalanced by the use of a decoupler. Finally the tunable 5-port junction used to feed in parallel each triplet of the second plug-in is analyzed by means of MWS simulation together with its decoupling-matching system.

  16. Analysis of plasma coupling with the prototype DIII-D ICRF antenna

    SciTech Connect

    Ryan, P.M.; Hoffman, D.J.; Bigelow, T.S.; Baity, F.W.; Gardner, W.L.; Mayberry, M.J.; Rothe, K.E.

    1988-01-01

    Coupling to plasma in the H-mode is essential to the success of future ignited machines such as CIT. To ascertain voltage and current requirements for high-power second harmonic heating (2 MW in a 35- by 50-cm port), coupling to the DIII-D tokamak with a prototype compact loop antenna has been measured. The results show good loading for L-mode and limiter plasmas, but coupling 2 MW to an H-mode plasma demands voltages and currents near the limit of present technology. We report the technological analysis and progress that allow coupling of these power densities. 5 refs., 4 figs.

  17. On resonant ICRF absorption in three-ion component plasmas: a new promising tool for fast ion generation

    NASA Astrophysics Data System (ADS)

    Kazakov, Ye. O.; Van Eester, D.; Dumont, R.; Ongena, J.

    2015-03-01

    We report on a very efficient ion-cyclotron-resonance-frequency (ICRF) absorption scheme (Z)-Y-X, which hinges on the presence of three ion species residing in the plasma. A mode conversion (cutoff-resonance) layer is well known to appear in two-ion species plasmas. If the location of the L-cutoff in Y-X plasmas, which can be controlled by varying the Y : X density ratio, almost coincides with the fundamental cyclotron resonance of the third ion species Z (resonant absorber), the latter—albeit present only in trace quantities—is shown to absorb almost all the incoming RF power. A quantitative criterion for the resonant Y : X plasma composition is derived and a few numerical examples are given. Since the absorbed power per resonant particle is much larger than for any other ICRF scheme, the here discussed scenarios are particularly promising for fast particle generation. Their possible application as a source of high-energy ions for the stellarator W7-X and to mimic alpha particles during the non-activated phase of ITER tokamak is briefly discussed.

  18. Comparison of 3-D Modeling With Experimental Results on Fast Wave Antenna Loading in DIII-D

    NASA Astrophysics Data System (ADS)

    Pinsker, R. I.; Ryan, P. M.; Goulding, R. H.; Hanson, G. R.; Milanesio, D.; Maggiora, R.; Hosea, J. C.; Nagy, A.; Porkolab, M.; Zeng, L.

    2011-10-01

    In DIII-D and other tokamaks, with a fixed system voltage limit, the parameter that limits the ICRF power that can be coupled to H-mode plasmas is the antenna loading resistance RL. For a fixed antenna geometry and excitation (phasing), RL is determined by the electron density profile in the antenna near-field region. Quantitative understanding of the coupling physics is obtained by comparing the resistive (RL) and reactive components of the antenna loading, without and with plasma, to predictions of 3-D models of the antenna and the edge plasma (Microwave Studio and TOPICA). When measured density profiles from reflectometers are used, good agreement between predicted and measured values of RL is obtained without any adjustable parameters in the model. The improved understanding is applied to enhancement of RL in advanced scenarios in DIII-D to increase the coupled fast wave power. Supported in part by US DOE under DE-FC02-04ER54698, DE-AC05-00OR22725, DE-AC02-09CH11466, DE-FG02-08ER54984.

  19. Effect of antenna geometry and plasma surface impedance on the directivity of fast wave antenna radiation

    SciTech Connect

    Heikkinen, J.A.; Pavlov, I.P.

    1996-02-01

    The fairly large poloidal directivity of a radiated fast wave spectrum related to the wave polarization relative to the ion gyration can be further enhanced by the nonperpendicular angle between the antenna current strap and the magnetic field. The latter is shown to be responsible also for the asymmetry in the parallel wavenumber spectrum of an unphased antenna, and can lead to deviations of order {le}30{percent} in the corresponding spectrum of a phased antenna array. The consequences of the observed effects to the antenna performance in the current drive applications as well as in excitation of poloidally asymmetric spectra are discussed. {copyright} {ital 1996 American Institute of Physics.}

  20. Technology of fast-wave current drive antennas

    SciTech Connect

    Hoffman, D.J.; Baity, F.W.; Goulding, R.H.; Haste, G.R.; Ryan, P.M.; Taylor, D.J.; Swain, D.W.; Mayberry, M.J.; Yugo, J.J.; General Atomics, San Diego, CA; Oak Ridge National Lab., TN )

    1989-01-01

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

  1. Effect of antenna orientation and plasma anisotropy on the directivity of fast wave antenna radiation

    SciTech Connect

    Pavlov, I.P.; Heikkinen, J.A.

    1995-10-01

    Asymmetry in the transverse wave number spectrum of the radiated power of a screenless fast wave antenna at an ion cyclotron range of frequencies is calculated with a model that takes into account the nonsymmetry of the plasma surface impedance matrix for an inhomogeneous tokamak plasma in front of the antenna. The directivity of the wave number spectrum transverse to the ambient magnetic field caused by the asymmetry in the surface impedance is found to be strongly asymmetric with respect to the parallel wave number by the effect of the nonperpendicular angle between the antenna current strap and the magnetic field. The latter is shown to be responsible also for the asymmetry in the parallel wave number spectrum of an undirected antenna, and can lead to deviations of order {le}30% in the corresponding spectrum of a phased antenna array with directivity. The consequences of the observed effects to the antenna performance in the current drive applications as well as in excitation of poloidally asymmetric spectra are discussed. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  2. Use of Fast Ion D-Alpha diagnostics for understanding ICRF effects

    SciTech Connect

    Podesta, M.; Heidbrink, W. W.; Liu, D.; Luo, Y.; Ruskov, E.; Bell, R. E.; Fredrickson, E. D.; Hosea, J. C.; Medley, S. S.; Burrell, K. H.; Choi, M.; Pinsker, R. I.; Harvey, R. W.

    2009-11-26

    Combined neutral beam injection and fast wave heating at cyclotron harmonics accelerate deuterium fast ions in the National Spherical Torus Experiment (NSTX) and in the DIII-D tokamak. Acceleration above the injected energy is evident in fast-ion D-alpha (FIDA) and volume-average neutron data. The FIDA diagnostic measures spatial profiles of the accelerated fast ions. In DIII-D, the acceleration is at a 4th or 5th cyclotron harmonic; the maximum enhancement in the high-energy FIDA signal is 8-10 cm beyond the resonance layer. In NSTX, acceleration is observed at five harmonics (7-11) simultaneously; overall, the profile of accelerated fast ions is much broader than in DIII-D. The energy distribution predicted by the CQL3D Fokker-Planck code agrees fairly well with measurements in DIII-D. However, the predicted profiles differ from experiment, presumably because the current version of CQL3D uses a zero-banana-width model.

  3. Use of the TFTR prototype charge exchange neutral analyzer for fast He/sub 3//sup + +/ diagnostics during ICRF heating on PLT

    SciTech Connect

    Medley, S.S.

    1981-07-01

    The Charge Exchange Neutral Analyzer (CENA) for TFTR is designed to measure singly charged ion species of atomic mass A = 1, 2, and 3 simultaneously with up to 75 energy channels per mass and an energy range of 0.5 < AE < 600, where AE is in units of AMU.keV. Plans to test the prototype analyzer on PLT prior to installation on TFTR are discussed. The capability of the analyzer to simultaneously measure singly reionized H, D, and He/sub 3/ charge exchange neutrals makes the analyzer of particular interest for recently proposed fast He/sub 3//sup + +/ diagnostics during ICRF heating on PLT.

  4. Global Confinement, Sawtooth Mixing, and Stochastic Diffusion Ripple Loss of Fast ICRF-driven H+ Minority Ions in TFTR

    SciTech Connect

    Petrov, M.P.; Bell, R.; Budny, R.V.; Gorelenkov, N.N.; Medley, S.S.; Zweben, S.J., PPPL

    1998-07-01

    This paper presents studies of ICRF-driven H+ minority ions in TFTR (Tokamak Fusion Test Reator) deuterium plasmas using primarily passive Ho flux detection in the energy range of 0.2-1.0 MeV with some corroborating active (lithium pellet charge exchange) measurements. It is shown that in the passive mode the main donors for the neutralization of H+ ions in this energy range are C5+ ions. The measured effective H+ tail temperatures range from 0.15 MeV at an ICRF power of 2 MW to 0.35 MeV at 6 MW. Analysis of the ICRF-driven H+ ion energy balance has been performed on the basis of the dependence of effective H+ temperatures on the plasma parameters. The analysis showed that H+ confinement times are comparable with their slowing-down times and tended to decrease with increasing ICRF power. Radial redistribution of ICRF-driven H+ ions was detected when giant sawtooth crashes occurred during the ICRF heating. The redistribution affected ions with energy below 0.7-0.8 MeV. The sawtooth crashes displace H+ ions outward along the plasma major radius into the stochastic ripple diffusion domain were those ions are lost in about 10 milliseconds. These observations are consistent with the model of the redistribution of energetic particles developed previously to explain the results of deuterium-tritium alpha-particle redistribution due to sawteeth observed in TFTR. The experimental data are also consistent with ORBIT code simulations of H+ stochastic ripple diffusion losses.

  5. Modeling of DC potential structures induced by RF sheaths with transverse currents in front of ICRF antenna

    SciTech Connect

    Faudot, E.; Heuraux, S.; Colas, L.

    2007-09-28

    RF heating is fully dependent on edge plasma conditions and particularly on convection of accelerated particles which can damage ICRH antennas (hot spots and impurity injection). These accelerated particle fluxes born in DC potential structures are induced by sheaths which rectify RF potentials. The potential map in front of antenna is not uniform so that transverse (to magnetic field) RF currents occur and can significantly modify the final DC potential map and thus convective flux distribution. The behavior of rectified potentials is investigated here for f = F{sub ci} and f>F{sub ci}, which was not yet achieved in our last works [1]. Therefore, a 2D fluid modeling including RF sheaths physics (parallel current) coupled with transverse RF currents has been built. The full description of the currents exhibits a maximum for frequencies around Fci, which can be explained by the fact that RF oscillation is capacitive at low frequency and inductive at high frequency. Both effects are present at frequencies around F{sub ci} and the DC peak potential appears for f = F{sub ci}/2. This is due to the rectification of the sinusoidal signal, which doubles the effective RF frequency radiated by the antenna. The theoretical DC peak value is 0.5 time the RF amplitude of the applied potential instead of 1/{pi} without transverse currents. For typical potential structures in front of ICRH antennas (centimetric wide and 1000 Volts peak potential), a factor between 0.4 and 0.45 can be expected according to 2D fiuid code results.

  6. Studies of ICRF Discharge Conditioning (ICRF-DC) on ASDEX Upgrade, JET and TEXTOR

    SciTech Connect

    Lyssoivan, A.; Koch, R.; Eester, D. van; Wassenhove, G. van; Vervier, M.; Weynants, R.; Gauthier, E.; Bobkov, V.; Fahrbach, H.-U.; Hartmann, D.A.; Rohde, V.; Suttrop, W.; Noterdaeme, J.-M.; Monakhov, I.; Walden, A.

    2005-09-26

    The present paper reviews the recent results achieved in the ICRF-DC experiments performed in helium/hydrogen mixtures in the non-circular tokamaks ASDEX Upgrade and JET and first tests of the ICRF discharges in helium/oxygen mixtures in the circular tokamak TEXTOR. Special emphasis was given to study the physics of ICRF discharges. A new recipe for safe and reliable RF plasma production [{approx}(3-5)x1017 m-3, Te{approx}(3-5) eV] with improved antenna coupling efficiency (by 1.5-3 times) and improved radial/poloidal homogeneity was proposed and successfully tested: coupling the RF power in the FW-IBW mode conversion scenario in plasmas with two ion species. The first results on ICRF wall conditioning in helium/hydrogen and in helium/oxygen mixtures are analyzed.

  7. Enhancement of Localized ICRF Heating and Current Drive in TFTR D-T Plasmas

    SciTech Connect

    = G Schilling, First Author

    1997-04-15

    Theoretical advantages have led to an increased importance of the modification and sustainment of pressure and magnetic shear profiles in plasmas. We have demonstrated electron heating and current drive in TFTR (Tokamak Fusion Test Reactor) plasmas with the existing 43/63.6 MHz ICRF (ion cyclotron range of frequencies) system, both via the fast wave and via mode conversion of the fast wave to an ion-Bernstein wave. In order to achieve both on- and off-axis mode conversion in a pure D-T (deuterium-tritium) plasma, we have changed the operating frequency of two of our transmitters and antennas to 30 MHz and improved the launched directional wave spectrum. As a second step, two new four-strap fast-wave antennas have been installed, and a new four-strap direct-launch IBW antenna has been added as well. This reconfiguration and the resulting operating characteristics of the TFTR ICRF system in a variety of discharges will be presented.

  8. Hybrid Couplers On The JET ICRF System: Commissioning And First Results on ELMs

    SciTech Connect

    Mayoral, M.-L.; Monakhov, I.; Walden, T.; Blackman, T.; Graham, M.; Mailloux, J.; Nigthingale, M.; Ongena, J.

    2007-09-28

    During the 2004-2005 shutdown, hybrid 3 dB couplers were installed between the A2 ICRF antennas A and B. The goal was to free one of the generators to power the new ITER-like ICRF antenna, but also to use the coupler properties to increase the ICRF power on ELMs. Furthermore, the fast data acquisition system was upgraded in order to monitor the forward and reflected voltage amplitudes with a time resolution up to 4 {mu}s. As expected, the first tests showed that the reflected powers during ELMs was successfully directed to the coupler dummy load instead of the generators and that a clear improvement in the averaged coupled power in the presence of the ELMs could be obtained. However, the existing levels of the VSWR protection against arcs appeared not satisfactory for ELM-tolerant operation and had to be re-assessed. Moreover, evidence of parasitic low-VSWR activity in the vacuum transmission lines was found, emphasizing the importance of developing VSWR independent arc detection systems.

  9. Analysis of ICRF-Accelerated Ions in ASDEX Upgrade

    SciTech Connect

    Mantsinen, M. J.; Eriksson, L.-G.; Noterdaeme, J.-M.

    2007-09-28

    MHD-induced losses of fast ions with energy in the MeV range have been observed during high-power ICRF heating of hydrogen minority ions in the ASDEX Upgrade tokamak (R{sub 0}{approx_equal}1.65 m, a{approx_equal}0.5 m). ICRF heating and ICRF-driven fast ions in discharges exhibiting fast ion losses due to toroidal Alfven eigenmodes and a new core-localised MHD instability are analysed. It is found that the lost ions are ICRF-accelerated trapped protons with energy in the range of 0.3-1.6 MeV, orbit widths of 20-35 cm, and turning points at r/a>0.5 and at major radii close to the cyclotron resonance {omega} = {omega}{sub cH}(R). The presence of such protons is consistent with ICRF modelling.

  10. Direct Electron Heating Observed by Fast Waves in ICRF Range on a Low-Density Low Temperature Tokamak ADITYA

    SciTech Connect

    Mishra, K.; Kulkarni, S.; Rathi, D.; Varia, A.; Jadav, H.; Parmar, K.; Kadia, B.; Joshi, R.; Srinivas, Y.; Singh, R.; Kumar, S.; Dani, S.; Gayatri, A.; Yogi, R.; Singh, M.; Joisa, Y.; Rao, C.; Kumar, S.; Jha, R.; Manchanda, R.

    2011-12-23

    Fast wave electron heating experiments are carried out on Aditya tokamak [R = 0.75 m, a = 0.25m,Bt = 0.75T,ne{approx}1-3E13/cc,Te{approx}250eV] with the help of indigenously developed 200 kW, 20-40 MHz RF heating system. Significant direct electron heating is observed by fast waves in hydrogen plasma with prompt rise in electron temperature with application of RF power and it increases linearly with RF power. A corresponding increase in plasma beta and hence increase in stored diamagnetic energy is also observed in presence of RF. We observe an improvement of energy confinement time from 2-4msec during ohmic heating phase to 3-6msec in RF heating phase. This improvement is within the ohmic confinement regime for the present experiments. The impurity radiation and electron density do not escalate significantly with RF power. The direct electron heating by fast wave in Aditya is also predicted by ion cyclotron resonance heating code TORIC.

  11. A TEM-horn antenna with dielectric lens for fast impulse response

    SciTech Connect

    Aurand, J.F.

    1995-12-31

    We designed and constructed a pair of TEM-horn antennas specifically for the very fast time-domain boresight response. Two physical topologies were made. A printed-board configuration has much slower transient response, which we think is due to pulse-smearing of the antenna currents in the dielectric substrate of the printed wiring boards. The solid state version has a 20 ps transition duration response in the main beam endfire (boresight) direction, which is the fastest we have seen to date. And since the antenna has a round trip antenna current propagation time of 6 ns, it offers clean radiated electromagnetic field measurement capability with a clear time of several nanoseconds. The printed board version has resistive loading at the aperture end of the conductors, which should offer better low- frequency performance. The dielectric lens certainly does improve the transient performance of the TEM horn, and was simple to design.

  12. Extension of Alcator C-Mod's ICRF experimental capability

    SciTech Connect

    Schilling, G.; Hosea, J. C.; Wilson, J. R.; Bonoli, P. T.; Lee, W. D.; Nelson-Melby, E.; Porkolab, M.; Wukitch, S. J.

    1999-09-20

    A new 4-strap single-ended ICRF antenna has been added to the Alcator C-Mod tokamak. PPPL designed, fabricated, and tested the antenna up to 45 kV on an rf test stand. It is capable of symmetric phasing for ICRF heating studies, and asymmetric phasing with an improved directed wave spectrum for current drive. Two new 2 MW transmitters, tunable from 40-80 MHz, allow operation in plasma at 43, 60, and 78 MHz to match a variety of toroidal fields and plasma conditions. This addition increases the total available ICRF power to 4 MW at 80 MHz plus 4 MW at 40-80 MHz. Plasma heating and current drive experiments at the extended power levels and new frequencies are planned, and initial system performance will be discussed. (c) 1999 American Institute of Physics.

  13. Extension of Alcator C-mod's ICRF Experimental Capability

    SciTech Connect

    Schilling, G.; Hosea, J.C.; Wilson, J.R.; Bonoli, P.T.; Lee, W.D.

    1999-06-01

    A new 4-strap single-ended ICRF antenna has been added to the Alcator C-Mod tokamak. PPPL designed, fabricated, and tested the antenna up to 45 kV on an rf test stand. It is capable of symmetric phasing for ICRF heating studies, and asymmetric phasing with an improved directed wave spectrum for current drive. Two new 2 MW transmitters, tunable from 40-80 MHz, allow operation in plasma at 43, 60, and 78 MHz to match a variety of toroidal fields and plasma conditions. This addition increases the total available ICRF power to 4 MW at 80 MHz plus 4 MW at 40-80 MHz. Plasma heating and current drive experiments at the extended power levels and new frequencies are planned, and initial system performance will be discussed.

  14. ICRF heating in JET during initial operations with the ITER-like wall

    NASA Astrophysics Data System (ADS)

    Jacquet, P.; Bobkov, V.; Brezinsek, S.; Brix, M.; Campergue, A.-L.; Colas, L.; Czarnecka, A.; Drewelow, P.; Graham, M.; Klepper, C. C.; Lerche, E.; Mayoral, M.-L.; Meigs, A.; Milanesio, D.; Monakhov, I.; Mlynar, J.; Pütterich, T.; Sirinelli, A.; Van-Eester, D.; JET-EFDA contributors

    2014-02-01

    In 2011/12, JET started operation with its new ITER-Like Wall (ILW) made of a tungsten (W) divertor and a beryllium (Be) main chamber wall. The impact of the new wall material on the JET Ion Cyclotron Resonance Frequency (ICRF) operation was assessed and also the properties of JET plasmas heated with ICRF were studied. No substantial change of the antenna coupling resistance was observed with the ILW as compared with the carbon wall. Heat-fluxes on the protecting limiters close the antennas quantified using Infra-Red (IR) thermography (maximum 4.5 MW/m2 in current drive phasing) are within the wall power load handling capabilities. A simple RF sheath rectification model using the antenna near-fields calculated with the TOPICA code can well reproduce the heat-flux pattern around the antennas. ICRF heating results in larger tungsten and nickel (Ni) contents in the plasma and in a larger core radiation when compared to Neutral Beam Injection (NBI) heating. Some experimental facts indicate that main-chamber W components could be an important impurity source: the divertor W influx deduced from spectroscopy is comparable when using RF or NBI at same power and comparable divertor conditions; the W content is also increased in ICRF-heated limiter plasmas; and Be evaporation in the main chamber results in a strong and long lasting reduction of the impurity level. The ICRF specific high-Z impurity content decreased when operating at higher plasma density and when increasing the hydrogen concentration from 5% to 20%. Despite the higher plasma bulk radiation, ICRF exhibited overall good plasma heating efficiency; The ICRF power can be deposited at plasma centre and the radiation is mainly from the outer part of the plasma. Application of ICRF heating in H-mode plasmas started, and the beneficial effect of ICRF central electron heating to prevent W accumulation in the plasma core could be observed.

  15. ICRF heating in JET during initial operations with the ITER-like wall

    SciTech Connect

    Jacquet, P.; Brix, M.; Graham, M.; Mayoral, M.-L.; Meigs, A.; Monakhov, I.; Sirinelli, A.; Brezinsek, S.; Campergue, A-L.; Colas, L.; Czarnecka, A.; Klepper, C. C.; Lerche, E.; Van-Eester, D.; Milanesio, D.; Mlynar, J.; Collaboration: JET-EFDA Contributors

    2014-02-12

    In 2011/12, JET started operation with its new ITER-Like Wall (ILW) made of a tungsten (W) divertor and a beryllium (Be) main chamber wall. The impact of the new wall material on the JET Ion Cyclotron Resonance Frequency (ICRF) operation was assessed and also the properties of JET plasmas heated with ICRF were studied. No substantial change of the antenna coupling resistance was observed with the ILW as compared with the carbon wall. Heat-fluxes on the protecting limiters close the antennas quantified using Infra-Red (IR) thermography (maximum 4.5 MW/m{sup 2} in current drive phasing) are within the wall power load handling capabilities. A simple RF sheath rectification model using the antenna near-fields calculated with the TOPICA code can well reproduce the heat-flux pattern around the antennas. ICRF heating results in larger tungsten and nickel (Ni) contents in the plasma and in a larger core radiation when compared to Neutral Beam Injection (NBI) heating. Some experimental facts indicate that main-chamber W components could be an important impurity source: the divertor W influx deduced from spectroscopy is comparable when using RF or NBI at same power and comparable divertor conditions; the W content is also increased in ICRF-heated limiter plasmas; and Be evaporation in the main chamber results in a strong and long lasting reduction of the impurity level. The ICRF specific high-Z impurity content decreased when operating at higher plasma density and when increasing the hydrogen concentration from 5% to 20%. Despite the higher plasma bulk radiation, ICRF exhibited overall good plasma heating efficiency; The ICRF power can be deposited at plasma centre and the radiation is mainly from the outer part of the plasma. Application of ICRF heating in H-mode plasmas started, and the beneficial effect of ICRF central electron heating to prevent W accumulation in the plasma core could be observed.

  16. Antenna design for fast ion collective Thomson scattering diagnostic for the international thermonuclear experimental reactor.

    PubMed

    Leipold, F; Furtula, V; Salewski, M; Bindslev, H; Korsholm, S B; Meo, F; Michelsen, P K; Moseev, D; Nielsen, S K; Stejner, M

    2009-09-01

    Fast ion physics will play an important role for the international thermonuclear experimental reactor (ITER), where confined alpha particles will affect and be affected by plasma dynamics and thereby have impacts on the overall confinement. A fast ion collective Thomson scattering (CTS) diagnostic using gyrotrons operated at 60 GHz will meet the requirements for spatially and temporally resolved measurements of the velocity distributions of confined fast alphas in ITER by evaluating the scattered radiation (CTS signal). While a receiver antenna on the low field side of the tokamak, resolving near perpendicular (to the magnetic field) velocity components, has been enabled, an additional antenna on the high field side (HFS) would enable measurements of near parallel (to the magnetic field) velocity components. A compact design solution for the proposed mirror system on the HFS is presented. The HFS CTS antenna is located behind the blankets and views the plasma through the gap between two blanket modules. The viewing gap has been modified to dimensions 30x500 mm(2) to optimize the CTS signal. A 1:1 mock-up of the HFS mirror system was built. Measurements of the beam characteristics for millimeter-waves at 60 GHz used in the mock-up agree well with the modeling. PMID:19791936

  17. Quench antenna and fast-motion investigations during training of a 7T dipole magnet

    SciTech Connect

    Lietzke, A.F.; Benjegerdes, R.; Bish, P.; Krywinski, J.; Scanlan, R.; Schmidt, R.; Taylor, C.

    1994-10-17

    Equipment was installed to detect fast conductor motion and quench propagation in a 1 meter long superconducting dipole magnet (1) The fast-motion antenna, centered within the bore of the magnet, used three long dipole coils, mounted end-to-end to span the magnet length. Coil signals were nulled against a neighbor to produce low-ripple signals that were sensitive to local flux changes. A low-microphonic signal was used as an event trigger. (2) Nulling improvements were made for the magnet`s coil-imbalance signals for improved cross-correlation information. (3) A quench-propagation antenna was installed to observe current redistribution during quench propagation. It consisted of quadrupole/sextupole coil sets distributed at three axial locations within the bore of the magnet. Signals were interpreted in terms of the radius, angle, orientation, and rate of change of an equivalent dipole. The magnet was cooled to 1.8K to maximize the number of events. Twenty-four fast-motion events occurred before the first quench. The signals were correlated with the magnet-coil imbalance signals. The quench-propagation antenna was installed for all subsequent quenches. Ramp-rate triggered quenches produced adequate signals for analysis, but pole-turn quenches yielded such small signals that angular localization of a quench was not precise.

  18. Gyrokinetic particle simulations of reversed shear Alfven eigenmode excited by antenna and fast ions

    SciTech Connect

    Deng Wenjun; Holod, Ihor; Xiao Yong; Lin Zhihong; Wang Xin; Zhang Wenlu

    2010-11-15

    Global gyrokinetic particle simulations of reversed shear Alfven eigenmode (RSAE) have been successfully performed and verified. We have excited the RSAE by initial perturbation, by external antenna, and by energetic ions. The RSAE excitation by antenna provides verifications of the mode structure, the frequency, and the damping rate. When the kinetic effects of the background plasma are artificially suppressed, the mode amplitude shows a near-linear growth. With kinetic thermal ions, the mode amplitude eventually saturates due to the thermal ion damping. The damping rates measured from the antenna excitation and from the initial perturbation simulation agree very well. The RSAE excited by fast ions shows an exponential growth. The finite Larmor radius effects of the fast ions are found to significantly reduce the growth rate. With kinetic thermal ions and electron pressure, the mode frequency increases due to the elevation of the Alfven continuum by the geodesic compressibility. The nonperturbative contributions from the fast ions and kinetic thermal ions modify the mode structure relative to the ideal magnetohydrodynamic (MHD) theory. The gyrokinetic simulations have been benchmarked with extended hybrid MHD-gyrokinetic simulations.

  19. Initial operation of high power ICRF system for long pulse in EAST

    NASA Astrophysics Data System (ADS)

    Qin, C. M.; Zhao, Y. P.; Zhang, X. J.; Wan, B. N.; Gong, X. Z.; Mao, Y. Z.; Yuan, S.; Chen, G.

    2015-12-01

    The ICRF heating system on EAST upgraded by active cooling aims for long pulse operation. In this paper, the main technical features of the ICRF system are described. One of a major challenges for long pulse operation is RF-edge interactions induced impurity production and heat loading. In EAST, ICRF antenna protections and Faraday screen bars damaged due to LH electron beam are found. Preliminary results for the analysis of the interaction between LHCD and ICRF antenna are discussed. Increase of metal impurities in the plasma during RF pulse and in a larger core radiation are also shown. These RF-edge interactions at EAST and some preliminary results for the optimizing RF performance will be presented.

  20. Initial operation of high power ICRF system for long pulse in EAST

    SciTech Connect

    Qin, C. M. Zhao, Y. P.; Zhang, X. J.; Wan, B. N.; Gong, X. Z.; Mao, Y. Z.; Yuan, S.; Chen, G.

    2015-12-10

    The ICRF heating system on EAST upgraded by active cooling aims for long pulse operation. In this paper, the main technical features of the ICRF system are described. One of a major challenges for long pulse operation is RF-edge interactions induced impurity production and heat loading. In EAST, ICRF antenna protections and Faraday screen bars damaged due to LH electron beam are found. Preliminary results for the analysis of the interaction between LHCD and ICRF antenna are discussed. Increase of metal impurities in the plasma during RF pulse and in a larger core radiation are also shown. These RF-edge interactions at EAST and some preliminary results for the optimizing RF performance will be presented.

  1. On the Use of EBG in ICRF and LH Launcher

    NASA Astrophysics Data System (ADS)

    Guadamuz, S.; Maggiora, R.; Vecchi, G.

    2009-11-01

    High impedance surfaces or electromagnetic band gap (EBG) surfaces have proved themselves to be useful in wireless communications applications due to their unique characteristics such as no propagating surface wave support, no conduction of RF current for a given bandwidth, in-phase electromagnetic reflection and non-inverted image of the electric charge in front of them [1]. These characteristics make possible to design compact antennas achieving better performance in terms of radiation and input impedance. ICRF and LH antennas in plasma experiments can take advantage of using EBG surfaces. One of the main issues in ICRF plasma heating is the low power coupling of the plasma facing antenna. The adoption of EBG surfaces in the ICRF antenna structure and the advantages offered by a predictive designing tool as TOPICA [2] offer the possibility to improve significantly the coupled power to plasma. The adoption of EBG surfaces in the LH waveguides permits to reduce the major dimension of waveguides not affecting drastically the propagation [3]. It is then possible to manufacture more compact LH arrays of waveguides.

  2. On the Use of EBG in ICRF and LH Launcher

    SciTech Connect

    Guadamuz, S.; Maggiora, R.; Vecchi, G.

    2009-11-26

    High impedance surfaces or electromagnetic band gap (EBG) surfaces have proved themselves to be useful in wireless communications applications due to their unique characteristics such as no propagating surface wave support, no conduction of RF current for a given bandwidth, in-phase electromagnetic reflection and non-inverted image of the electric charge in front of them. These characteristics make possible to design compact antennas achieving better performance in terms of radiation and input impedance. ICRF and LH antennas in plasma experiments can take advantage of using EBG surfaces. One of the main issues in ICRF plasma heating is the low power coupling of the plasma facing antenna. The adoption of EBG surfaces in the ICRF antenna structure and the advantages offered by a predictive designing tool as TOPICA offer the possibility to improve significantly the coupled power to plasma. The adoption of EBG surfaces in the LH waveguides permits to reduce the major dimension of waveguides not affecting drastically the propagation. It is then possible to manufacture more compact LH arrays of waveguides.

  3. MW-scale ICRF plasma heating using IGBT switches in a multi-pulse scheme

    NASA Astrophysics Data System (ADS)

    Be'ery, I.; Kogan, K.; Seemann, O.

    2015-06-01

    Solid-state silicon switches are cheap and reliable option for 1-10 MHz RF power sources, required for plasma ion cyclotron RF heating (ICRF). The large `on' resistance of MOSFET and similar devices limits their power delivery to a few tens of kW per switch. Low resistivity devices, such as IGBT, suffer from large `off' switching time, which limits their useful frequency range and increases the power dissipated in the switch. Here we demonstrate more than 0.8 MW circulated RF power at 2 MHz using only three high voltage IGBT switches. The circuit uses the fast `on' switching capability of the IGBTs to generate high-Q pulse train. This operation mode also simplifies the measurement of RF coupling between the antenna and the plasma.

  4. Design Concepts For A Long Pulse Upgrade For The DIII-D Fast Wave Antenna Array

    SciTech Connect

    Ryan, Philip Michael; Baity Jr, F Wallace; Caughman, John B; Goulding, Richard Howell; Hosea, J.; Greenough, Nevell; Nagy, Alex; Pinsker, R.; Rasmussen, David A

    2009-01-01

    A goal in the 5-year plan for the fast wave program on DIII-D is to couple a total of 3.6 MW of RF power into a long pulse, H-mode plasma for central electron heating. The present short-pulse 285/300 antenna array would need to be replaced with one capable of at least 1.2 MW, 10 s operation at 60 MHz into an H-mode (low resistive loading) plasma condition. The primary design under consideration uses a poloidally-segmented strap (3 sections) for reduced strap voltage near the plasma/Faraday screen region. Internal capacitance makes the antenna structure self-resonant at 60 MHz, strongly reducing peak E-fields in the vacuum coax and feed throughs.

  5. Design Concepts For A Long Pulse Upgrade For The DIII-D Fast Wave Antenna Array

    SciTech Connect

    Ryan, P. M.; Baity, F. W.; Caughman, J. B. O.; Goulding, R. H.; Rasmussen, D. A.; Hosea, J. C.; Greenough, N. L.; Nagy, A.; Pinsker, R. I.

    2009-11-26

    A goal in the 5-year plan for the fast wave program on DIII-D is to couple a total of 3.6 MW of RF power into a long pulse, H-mode plasma for central electron heating. The present short-pulse 285/300 antenna array would need to be replaced with one capable of at least 1.2 MW, 10 s operation at 60 MHz into an H-mode (low resistive loading) plasma condition. The primary design under consideration uses a poloidally-segmented strap (3 sections) for reduced strap voltage near the plasma/Faraday screen region. Internal capacitance makes the antenna structure self-resonant at 60 MHz, strongly reducing peak E-fields in the vacuum coax and feed throughs.

  6. ICRF heating in Alcator C-Mod: Present status and future prospects

    SciTech Connect

    Porkolab, M.; Fiore, C.; Greenwald, M.; Hosea, J. C.; Hubbard, A.; Hutchinson, I.; Irby, J.; Nelson-Melby, E.; Marmar, E.; Phillips, C. K.

    1999-09-20

    Alcator C-Mod, the high field, high density, diverted, compact tokamak in the world's portfolio of high performance plasma fusion devices, is heated exclusively with ICRF auxiliary power. In this paper an overview of recent results is summarized, with particular attention given to the importance of RF operation and the flexibility afforded by different heating scenarios. Besides the routine minority heating operation, results in the mode conversion heating regime are also presented (mainly direct electron heating through mode converted ion Bernstein waves). Recent attempts at improving plasma performance by establishing internal transport barriers (ITBs) by various transient profile control techniques (the so-called Advanced Tokamak mode of operation) are also presented. Future improvements in performance afforded by the recent addition of a new 4-strap antenna and 4 MW of tunable (40-80 MHz) ICRF power are also discussed. Mode-conversion current drive (MCCD) and fast wave current drive (FWCD) will be among the many new options that will be tested with the goal of improving plasma performance. (c) 1999 American Institute of Physics.

  7. Comparative study of fundamental and second-harmonic ICRF wave propagation and damping at high density in the Alcator tokamak

    SciTech Connect

    Gaudreau, M.P.J.

    1981-09-01

    Due to the versatility of the high power apparatus, the fast magnetosonic branch is used with ..omega../sub 0/ = 1,2,3,4 ..omega../sub ci/, unlike most other ICRF experiments. Unusually high magnetic field (B/sub 0/ = 40 to 80 kG), plasma density (n/sub e/ = 10/sup 13/ - 5 x 10/sup 14//cm/sup 3/), generator frequency (f/sub 0/ = 90 to 200 MHz) and transmitter power, with shielded and unshielded antennas, are the key parameters of the experiment. This wide parameter range allows a direct comparison between fundamental and second harmonic regimes, and shielded and unshielded antennas, our prime goals. The real and imaginary parts of the parallel and perpendicular wave numbers are measured with extensive magnetic probe diagnostics for a spectrum of plasma parameters and compared with theory. Qualitative and quantitative evaluations of the wave structure and scaling laws are derived analytically in simple geometries and computed numerically for realistic plasma parameters and profiles. General figures of merit, such as radiation resistance and quality factor, are also derived and compared with the experiment. Secondary effects of the high power wave launching, such as changes in plasma current, density, Z/sub eff/, energetic neutral flux, soft x-rays, neutron flux, and impurities are also discussed. Most important, a general synthesis of the many engineering, physics, and experimental problems and conclusions of the Alcator A ICRF program are inspected in detail. Finally, the derived and experimentally determined scaling laws and engineering constraints are used to estimate the ICRF requrements, advantages, and potential pitfalls of the next generations of experiments on the Alcator tokamaks.

  8. Experimental Study of RF Sheath Formation on a Fast Wave Antenna and Limiter in the LAPD

    NASA Astrophysics Data System (ADS)

    Martin, Michael; Gekelman, Walter; Pribyl, Patrick; van Compernolle, Bart; Carter, Troy

    2015-11-01

    Ion cyclotron resonance heating (ICRH) will be an essential component of heating power in ITER. During ICRH, radio frequency (RF) sheaths may form both at the exciting antenna and further away, e.g. in the divertor region, and may cause wall material sputtering and decreased RF power coupling to the plasma. It is important to do detailed laboratory experiments that fully diagnose the sheaths and wave fields. This is not possible in fusion devices. A new RF system has recently been constructed for performing such studies in the LAPD plasma column (ne ~1012 -1013cm-3 , Te ~ 1 - 10 eV ,B0 ~ 400 - 2000 G , diameter ~ 60cm , length ~ 18 m) . The RF system is capable of pulsing at the 1 Hz rep. rate of the LAPD plasma and operating between 2-6 MHz (1st - 9th harmonic of fci in H) with a power output of 200 kW. First results of this system driving a single-strap fast wave antenna will be presented. Emissive and Langmuir probe measurements in the vicinity of both the antenna and a remote limiter and wave coupling measured by magnetic pickup loops will be presented.

  9. LH Wave Coupling And ICRF Sheaths At JET

    SciTech Connect

    Kirov, K. K.; Baranov, Yu.; Erents, K.; Jacquet, P.; Mailloux, J.; Mayoral, M.-L.; Stamp, M.; Petrzilka, V.

    2007-09-28

    Lower Hybrid (LH) wave coupling deteriorates when the system is pulsed with Ion Cyclotron Range of Frequencies (ICRF) antennas magnetically connected to the launcher. This has been attributed to the density modifications by the RF sheaths. Reflection Coefficients (RCs) dependencies are investigated and shown consistent with the sheath physics. Gas puffing near the launcher has been used to improve the coupling. Results from a statistical analysis of a particular set of data are summarised.

  10. Power Compensation for ICRF Heating in EAST

    NASA Astrophysics Data System (ADS)

    Chen, Gen; Qin, Chengming; Mao, Yuzhou; Zhao, Yanping; Yuan, Shuai; Zhang, Xinjun

    2016-08-01

    The source system covering a working frequency range of 24 MHz to 70 MHz with a total maximum output power of 12 MW has already been fabricated for Ion Cyclotron Range of Frequency (ICRF) heating in EAST from 2012. There are two continuous wave (CW) antennas consisting of four launching elements each fed by a separate 1.5 MW transmitter. Due to the strong mutual coupling among the launching elements, the injection power for launching elements should be imbalance to keep the k‖ (parallel wave number) spectrum of the launcher symmetric for ICRF heating. Cross power induced by the mutual coupling will also induce many significant issues, such as an uncontrollable phase of currents in launching elements, high voltage standing wave ratio (VSWR), and impedance mismatching. It is necessary to develop a power compensation system for antennas to keep the power balance between the feed points. The power balance system consists of two significant parts: a decoupler and phase control. The decoupler helps to achieve ports isolation to make the differential phase controllable and compensate partly cross power. After that, the differential phase of 0 or π will keep the power balance of two feed points completely. The first power compensation system consisting of four decouplers was assembled and tested for the port B antenna at the working frequency of 35 MHz. With the application of the power compensation system, the power balance, phase feedback control, and voltage standing wave ratio (VSWR) had obviously been improved in the 2015 EAST campaign. supported by the National Magnetic Confinement Fusion Science Program of China (No. 2015GB101001) and National Natural Science Foundation of China (Nos. 11575237, 11375235, 11375236)

  11. ICRF array module development and optimization for high power density

    SciTech Connect

    Ryan, P.M.; Swain, D.W.

    1997-02-01

    This report describes the analysis and optimization of the proposed International Thermonuclear Experimental Reactor (ITER) Antenna Array for the ion cyclotron range of frequencies (ICRF). The objectives of this effort were to: (1) minimize the applied radiofrequency rf voltages occurring in vacuum by proper layout and shape of components, limit the component`s surface/volumes where the rf voltage is high; (2) study the effects of magnetic insulation, as applied to the current design; (3) provide electrical characteristics of the antenna for the development and analysis of tuning, arc detection/suppression, and systems for discriminating between arcs and edge-localized modes (ELMs); (4) maintain close interface with mechanical design.

  12. RF-sheath assessment of ICRF Faraday Screens

    SciTech Connect

    Colas, L.

    2007-09-28

    The line-integrated parallel RF electric field {delta}V{sub RF} is studied on 'long field lines' radially in front of an ICRF antenna closed by a Faraday screen (FS). Several issues are addressed analytically and numerically. To what extent is a FS necessary to shield {delta}V{sub RF} in presence of magnetized plasma, depending on strap phasing? How efficient is it as a function of FS misalignment on tilted magnetic field? Can a FS attenuate {delta}V{sub RF} produced on antenna frame?.

  13. Antennae

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Atlas Image mosaic, covering 7' x 7' on the sky of the interacting galaxies NGC 4038 and NGC 4039, better known as the Antennae, or Ring Tail galaxies. The two galaxies are engaged in a tug-of-war as they collide. The mutual gravitation between them is working to distort each spiral galaxy's appearance as the two merge. The interaction is evidently impetus for an intense burst of new star formation, as can be seen from the many infrared-bright knots and bright galactic nuclei. Compare the 2MASS view of this system with that obtained by the Hubble Space Telescope in the optical. Many of the same features are seen, although 2MASS is able to peer through much of the dust seen in the galaxies' disks. The galaxy light looks smoother. Also, in the near-infrared the bright knots of star formation are likely highlighted by the light of massive red supergiant stars. The much more extended 'tidal tails,' which give the Antennae their name, are quite faint in the 2MASS image mosaic.

  14. Monte Carlo simulation of ICRF discharge initiation in ITER

    NASA Astrophysics Data System (ADS)

    Tripský, M.; Wauters, T.; Lyssoivan, A.; Křivská, A.; Louche, F.; Van Schoor, M.; Noterdaeme, J.-M.

    2015-12-01

    Discharges produced and sustained by ion cyclotron range of frequency (ICRF) waves in absence of plasma current will be used on ITER for (ion cyclotron-) wall conditioning (ICWC). The here presented simulations aim at ensuring that the ITER ICRH&CD system can be safely employed for ICWC and at finding optimal parameters to initiate the plasma. The 1D Monte Carlo code RFdinity1D3V was developed to simulate ICRF discharge initiation. The code traces the electron motion along one toroidal magnetic field line, accelerated by the RF field in front of the ICRF antenna. Electron collisions in the calculations are handled by a Monte Carlo procedure taking into account their energies and the related electron collision cross sections for collisions with H2, H2+ and H+. The code also includes Coulomb collisions between electrons and ions (e - e, e - H2+ , e - H+). We study the electron multiplication rate as a function of the RF discharge parameters (i) antenna input power (0.1-5MW), and (ii) the neutral pressure (H2) for two antenna phasing (monopole [0000]-phasing and small dipole [0π0π]-phasing). Furthermore, we investigate the electron multiplication rate dependency on the distance from the antenna straps. This radial dependency results from the decreasing electric amplitude and field smoothening with increasing distance from the antenna straps. The numerical plasma breakdown definition used in the code corresponds to the moment when a critical electron density nec for the low hybrid resonance (ω = ωLHR) is reached. This numerical definition was previously found in qualitative agreement with experimental breakdown times obtained from the literature and from experiments on the ASDEX Upgrade and TEXTOR.

  15. Reflectometer sensing of rf waves in front of the high harmonic fast wave antenna on NSTX

    SciTech Connect

    Wilgen, J. B.; Ryan, P. M.; Hanson, G. R.; Swain, D. W.; Bernabei, S. I.; Greenough, N.; DePasquale, S.; Phillips, C. K.; Hosea, J. C.; Wilson, J. R.

    2006-10-15

    The ability to measure rf driven waves in the edge of the plasma can help to elucidate the role that surface waves and parametric decay instabilities (PDIs) play in rf power losses on NSTX. A microwave reflectometer has recently been modified to monitor rf plasma waves in the scrape-off layer in front of the 30 MHz high harmonic fast wave antenna array on NSTX. In rf heated plasmas, the plasma-reflected microwave signal exhibits 30 MHz sidebands, due primarily to the modulation of the cutoff layer by the electrostatic component of the heating wave. Similarly, electrostatic parametric decay waves (when present) are detected at frequencies below the heating frequency, near 28, 26,... MHz, separated from the heating frequency by harmonics of the local ion cyclotron frequency of about 2 MHz. In addition, a corresponding frequency matched set of decay waves is also detected near the ion cyclotron harmonics at 2, 4,... MHz. The rf plasma-wave sensing capability is useful for determination of the PDI power threshold as a function of antenna array phasing (including toroidal wavelength), outer gap spacing, and various plasma parameters such as the magnetic field and the plasma current.

  16. Analytic Model of Antenna Sheaths

    NASA Astrophysics Data System (ADS)

    D'Ippolito, D. A.; Myra, J. R.

    2008-11-01

    RF sheaths are generated on ICRF antennas whenever the launched fast wave also drives a slow wave, e.g. when the magnetic field is tilted (not perpendicular to the current straps). A new approach to sheath modeling was recently proposed in which the RF waves are computed using a modified boundary condition at the sheath surface to describe the plasma-sheath coupling. Here, we illustrate the use of the sheath BC for antenna sheaths by a model electromagnetic perturbation calculation, treating the B field tilt as a small parameter. Analytic expressions are obtained for the sheath voltage and the rf electric field parallel to B in both sheath and plasma regions, including the Child-Langmuir (self-consistency) constraint. It is shown that the plasma corrections to the sheath voltage (which screen the rf field) can be important. The simple vacuum-field sheath-voltage estimate is obtained as a limiting case. Implications for antenna codes such as TOPICA will be discussed. D.A. D'Ippolito and J.R. Myra, Phys. Plasmas 13, 102508 (2006). V. Lancellotti et al., Nucl. Fusion 46, S476 (2006).

  17. High-power and steady-state operation of ICRF heating in the large helical device

    NASA Astrophysics Data System (ADS)

    Mutoh, T.; Seki, T.; Saito, K.; Kasahara, H.; Seki, R.; Kamio, S.; Kumazawa, R.; Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Takahashi, H.; , T., Ii; Makino, R.; Nagaoka, K.; Nomura, G.; Shinya, T.

    2015-12-01

    Recent progress in an ion cyclotron range of frequencies (ICRF) heating system and experiment results in a Large Helical Device (LHD) are reported. Three kinds of ICRF antenna pairs were installed in the LHD, and the operation power regimes were extended up to 4.5 MW; also, the steady-state operation was extended for more than 45 min in LHD at a MW power level. We studied ICRF heating physics in heliotron configuration using a Hand Shake type (HAS) antenna, Field Aligned Impedance Transforming (FAIT) antenna, and Poloidal Array (PA) antenna, and established the optimum minority-ion heating scenario in an LHD. The FAIT antenna having a novel impedance transformer inside the vacuum chamber could reduce the VSWR and successfully injected a higher power to plasma. We tested the PA antennas completely removing the Faraday-shield pipes to avoid breakdown and to increase the plasma coupling. The heating performance was almost the same as other antennas; however, the heating efficiency was degraded when the gap between the antenna and plasma surface was large. Using these three kinds of antennas, ICRF heating could contribute to raising the plasma beta with the second- and third-harmonic cyclotron heating mode, and also to raising the ion temperature as discharge cleaning tools. In 2014, steady-state operation plasma with a line-averaged electron density of 1.2 × 1019 m-3, ion and electron temperature of 2 keV, and plasma sustainment time of 48 min was achieved with ICH and ECH heating power of 1.2 MW for majority helium with minority hydrogen. In 2015, the higher-power steady-state operation with a heating power of up to 3 MW was tested with higher density of 3 × 1019 m-3.

  18. High-power and steady-state operation of ICRF heating in the large helical device

    SciTech Connect

    Mutoh, T. Seki, T.; Saito, K.; Kasahara, H.; Seki, R.; Kamio, S.; Kumazawa, R.; Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Takahashi, H.; Ii, T.; Makino, R.; Nagaoka, K.; Nomura, G.; Shinya, T.

    2015-12-10

    Recent progress in an ion cyclotron range of frequencies (ICRF) heating system and experiment results in a Large Helical Device (LHD) are reported. Three kinds of ICRF antenna pairs were installed in the LHD, and the operation power regimes were extended up to 4.5 MW; also, the steady-state operation was extended for more than 45 min in LHD at a MW power level. We studied ICRF heating physics in heliotron configuration using a Hand Shake type (HAS) antenna, Field Aligned Impedance Transforming (FAIT) antenna, and Poloidal Array (PA) antenna, and established the optimum minority-ion heating scenario in an LHD. The FAIT antenna having a novel impedance transformer inside the vacuum chamber could reduce the VSWR and successfully injected a higher power to plasma. We tested the PA antennas completely removing the Faraday-shield pipes to avoid breakdown and to increase the plasma coupling. The heating performance was almost the same as other antennas; however, the heating efficiency was degraded when the gap between the antenna and plasma surface was large. Using these three kinds of antennas, ICRF heating could contribute to raising the plasma beta with the second- and third-harmonic cyclotron heating mode, and also to raising the ion temperature as discharge cleaning tools. In 2014, steady-state operation plasma with a line-averaged electron density of 1.2 × 10{sup 19} m{sup −3}, ion and electron temperature of 2 keV, and plasma sustainment time of 48 min was achieved with ICH and ECH heating power of 1.2 MW for majority helium with minority hydrogen. In 2015, the higher-power steady-state operation with a heating power of up to 3 MW was tested with higher density of 3 × 10{sup 19} m{sup −3}.

  19. ICRF specific plasma wall interactions in JET with the ITER-like wall

    NASA Astrophysics Data System (ADS)

    Bobkov, Vl.; Arnoux, G.; Brezinsek, S.; Coenen, J. W.; Colas, L.; Clever, M.; Czarnecka, A.; Braun, F.; Dux, R.; Huber, A.; Jacquet, P.; Klepper, C.; Lerche, E.; Maggi, C.; Marcotte, F.; Maslov, M.; Matthews, G.; Mayoral, M. L.; McCormick, K.; Meigs, A.; Milanesio, D.; Monakhov, I.; Neu, R.; Noterdaeme, J.-M.; Pütterich, Th.; Rimini, F.; Van Rooj, G.; Sergienko, G.; Van Eester, D.

    2013-07-01

    A variety of plasma wall interactions (PWIs) during operation of the so-called A2 ICRF antennas is observed in JET with the ITER-like wall. Amongst effects of the PWIs, the W content increase is the most significant, especially at low plasma densities. No increase of W source from the main divertor and entrance of the outer divertor during ICRF compared to NBI phases was found by means of spectroscopic and WI (400.9 nm) imaging diagnostics. In contrary, the W flux there is higher during NBI. Charge exchange neutrals of hydrogen isotopes could be excluded as considerable contributors to the W source. The high W content in ICRF heated limiter discharges suggests the possibility of other W sources than the divertor alone. Dependencies of PWIs to individual ICRF antennas during q95-scans, and intensification of those for the -90° phasing, indicate a link between the PWIs and the antenna near-fields. The PWIs include heat loads and Be sputtering pattern on antenna limiters. Indications of some PWIs at the outer divertor entrance are observed which do not result in higher W flux compared to the NBI phases, but are characterized by small antenna-specific (up to 25% with respect to ohmic phases) bipolar variations of WI emission. The first TOPICA calculations show a particularity of the A2 antennas compared to the ITER antenna, due to the presence of long antenna limiters in the RF image current loop and thus high near-fields across the most part of the JET outer wall.

  20. ICRF Specific Plasma Wall Interactions in JET with the ITER-Like Wall

    SciTech Connect

    Bobkov, V.; Arnoux, G.; Brezinsek, S.; Coenen, J. W.; Colas, L.; Clever, M.; Czarnecka, A.; Braun, F.; Dux, R.; Huber, Alexander; Lerche, E.; Maggi, C.; Marcotte, F.; Maslov, M.; Matthews, G.; Mayoral, M.-L.; Meigs, A. G.; Monakhov, I.; Putterich, Th.; Rimini, F.; Rooj, G. Van; Sergienko, G.; Van Eester, D.

    2013-01-01

    A variety of plasma wall interactions (PWIs) during operation of the so-called A2 ICRF antennas is observed in JET with the ITER-like wall. Amongst effects of the PWIs, the W content increase is the most significant, especially at low plasma densities. No increase of W source from the main divertor and entrance of the outer divertor during ICRF compared to NBI phases was found by means of spectroscopic and WI (400.9 nm) imaging diagnostics. In contrary, the W flux there is higher during NBI. Charge exchange neutrals of hydrogen isotopes could be excluded as considerable contributors to the W source. The high W content in ICRF heated limiter discharges suggests the possibility of other W sources than the divertor alone. Dependencies of PWIs to individual ICRF antennas during q95-scans, and intensification of those for the 90 phasing, indicate a link between the PWIs and the antenna near-fields. The PWIs include heat loads and Be sputtering pattern on antenna limiters. Indications of some PWIs at the outer divertor entrance are observed which do not result in higher W flux compared to the NBI phases, but are characterized by small antenna-specific (up to 25% with respect to ohmic phases) bipolar variations of WI emission. The first TOPICA calculations show a particularity of the A2 antennas compared to the ITER antenna, due to the presence of long antenna limiters in the RF image current loop and thus high near-fields across the most part of the JET outer wall.

  1. The IGNITOR ICRF system

    NASA Astrophysics Data System (ADS)

    Kyrytsya, Volodymyr; Maggiora, Riccardo; Lancellotti, Vito; Milanesio, Daniele; Vecchi, Giuseppe

    2006-10-01

    A flexible auxiliary Ion Cyclotron Resonance Heating (ICRH) system (f = 80 -- 120 MHz) has been included in the IGNITOR machine design. ICRH systems have been successfully tested on a number of existing devices especially at high density. Ignition can be accelerated significantly by relatively low levels of ICRH (about 5 MW, a fraction of the final fusion heating) when applied during the current ramp-up. In addition, ICRH provides a useful tool to control the evolution of the current density profile. Four antennas, each composed by 2 straps, 4 tuning stubs, and 2 generators each, can deliver a minimum RF power of about 12 MW for the entire adopted frequency range. The possibility of adding two more antennas has been considered. The antenna design has been based on performance evaluation obtained with the TOPICA simulation suite (Torino Polytechnic Ion Cyclotron Antenna code).

  2. Modification of Sawtooth Oscillations with ICRF Waves in the JET Tokamak

    SciTech Connect

    Mantsinen, M. J.; Alper, B.; Buttery, R.; Howell, D.; Kiptily, V.; Mayoral, M.-L.; Sharapov, S. E.; Coda, S.; Graves, J. P.; Sauter, O.; Eriksson, L.-G.; Lennholm, M.; Ingesson, L. C.; Nabais, F.; Nave, F.

    2007-09-28

    Methods of modifying sawtooth oscillations using waves in the ion cyclotron range of frequencies (ICRF) in the JET tokamak are presented. Examples of sawtooth stabilization by ICRF-accelerated high-energy ions are shown, including experiments with ICRF-acceleration of {sup 4}He-beam ions to simulate the effects of fusion born alpha particles. With high power ICRF heating in low-density plasmas, fast ion stabilization of sawteeth is lost and a new type of small-period and small-amplitude sawteeth appears. ICRF-induced radial pinch with toroidally asymmetric waves is found to be useful in affecting the radial profile of the ICRF-driven fast ion populations and thereby their influence on sawteeth. Ion cyclotron current drive (ICCD) applied close to the sawtooth inversion radius is effective in modifying the sawtooth period. The latest achievements include the successful application of ICCD to shorten the fast-ion-induced long-period sawteeth and thereby avoid triggering of neoclassical tearing modes (NTMs)

  3. Modeling and simulation support for ICRF heating of fusion plasmas. Annual report, 1990

    SciTech Connect

    1990-03-15

    Recent experimental, theoretical and computational results have shown the need and usefulness of a combined approach to the design, analysis and evaluation of ICH antenna configurations. The work at the University of Wisconsin (UW) in particular has shown that much needed information on the vacuum operation of ICH antennas can be obtained by a modest experimental and computational effort. These model experiments at UW and SAIC simulations have shown dramatically the potential for positive impact upon the ICRF program. Results of the UW-SAIC joint ICRF antenna analysis effort have been presented at several international meetings and numerous meetings in the United States. The PPPL bay M antenna has been modeled using the ARGUS code. The results of this effort are shown in Appendix C. SAIC has recently begun a collaboration with the ICRF antenna design and analysis group at ORNL. At present there are two separate projects underway. The first is associated with the simulation of and determination of the effect of adding slots in the antenna septum and side walls. The second project concerns the modeling and simulation of the ORNL folded waveguide (FWG) concept.

  4. ICRF Heating and Beta Enhancement of HBT-EP Plasmas

    NASA Astrophysics Data System (ADS)

    James, R.; Cates, C.; Klein, A.; Liu, Y.; Mauel, M. E.; Maurer, D. A.; Navratil, G. A.; Pedersen, T. S.; Shilov, M.; Stillits, N.

    2004-11-01

    We describe experiments using the HBT-EP dual strap, inside launch ICRF heating system. RF heating is applied at 4.5MHz to deuterium discharges with 20 percent hydrogen minority species in order to heat electrons in the strongly damped mode-conversion regime. Experiments to date have shown antenna loading with plasmas pre-programmed to be strongly limited on the high field side (HFS) limiter. A HFS triple probe measures electron temperature and density near the antenna, and an RF pickup coil is employed to measure the fluctuating wave magnetic field. Experiments to date indicate that increased plasma density near the antenna improves coupling significantly. We will report on our progress in improving antenna-plasma coupling using the radial position feedback control system (RPFCS) in conjunction with the bias probe to achieve high plasma density near the antenna. Any bias probe induced H-modes may also help increase antenna coupling by increasing the plasma density near the edge. Progress on analysis and diagnosis of the antenna-oscillator circuit and loading measurements and current status of measurable RF heating will be presented.[1] [1] Collaboration with J. Hosea, R. Wilson, R. Budny, S. Paul et al., PPPL

  5. Fast terahertz optoelectronic amplitude modulator based on plasmonic metamaterial antenna arrays and graphene

    NASA Astrophysics Data System (ADS)

    Jessop, David S.; Sol, Christian W. O.; Xiao, Long; Kindness, Stephen J.; Braeuninger-Weimer, Philipp; Lin, Hungyen; Griffiths, Jonathan P.; Ren, Yuan; Kamboj, Varun S.; Hofmann, Stephan; Zeitler, J. Axel; Beere, Harvey E.; Ritchie, David A.; Degl'Innocenti, Riccardo

    2016-02-01

    The growing interest in terahertz (THz) technologies in recent years has seen a wide range of demonstrated applications, spanning from security screening, non-destructive testing, gas sensing, to biomedical imaging and communication. Communication with THz radiation offers the advantage of much higher bandwidths than currently available, in an unallocated spectrum. For this to be realized, optoelectronic components capable of manipulating THz radiation at high speeds and high signal-to-noise ratios must be developed. In this work we demonstrate a room temperature frequency dependent optoelectronic amplitude modulator working at around 2 THz, which incorporates graphene as the tuning medium. The architecture of the modulator is an array of plasmonic dipole antennas surrounded by graphene. By electrostatically doping the graphene via a back gate electrode, the reflection characteristics of the modulator are modified. The modulator is electrically characterized to determine the graphene conductivity and optically characterization, by THz time-domain spectroscopy and a single-mode 2 THz quantum cascade laser, to determine the optical modulation depth and cut-off frequency. A maximum optical modulation depth of ~ 30% is estimated and is found to be most (least) sensitive when the electrical modulation is centered at the point of maximum (minimum) differential resistivity of the graphene. A 3 dB cut-off frequency > 5 MHz, limited only by the area of graphene on the device, is reported. The results agree well with theoretical calculations and numerical simulations, and demonstrate the first steps towards ultra-fast, graphene based THz optoelectronic devices.

  6. Status of the ITER ICRF system design - 'Externally Matched' approach

    SciTech Connect

    Lamalle, P. U.; Dumortier, P.; Durodie, F.; Evrard, M.; Louche, F.; Messiaen, A.; Vervier, M.; Shannon, M.; Borthwick, A.; Chuilon, B.; Nightingale, M.; Goulding, R.; Swain, D.

    2007-09-28

    The design of the ITER ICRF system has been under revision for several years. The paper presents the status of the design proposal based on a 24 strap antenna plug (6 poloidal by 4 toroidal short radiating conductors) in which the straps are passively combined in 8 poloidal triplets by means of 4-port junctions. These triplets are connected in parallel pairwise through matching elements to form 4 load-resilient conjugate-T circuits. All adjustable matching elements are located outside the plug, i.e. in the ITER port cell and in the generator area.

  7. Measurement of the ICRF wave propagation in the internal region of plasmas by using reflectometers on GAMMA10

    NASA Astrophysics Data System (ADS)

    Okada, T.; Ikezoe, R.; Ichimura, M.; Hirata, M.; Sakamoto, M.; Sumida, S.; Iwamoto, Y.; Jang, S.; Itagaki, J.; Onodera, Y.; Yoshikawa, M.; Kohagura, J.; Shima, Y.; Nakashima, Y.

    2015-11-01

    ICRF waves is one of valuable tools for producing and heating plasmas. On GAMMA10, ions are mainly heated by the ICRF waves with the absorption of the cyclotron resonance layers. ICRF waves of 6.36, 9.9 and 10.3 MHz are normally used to be compatible with the magnetic mirror configuration and damped at the resonance layers of the central cell, east and west anchor cells, respectively. These waves are usually excited by ICRF antennas installed in the central cell and propagate to each resonance layer. It is essential for the ongoing divertor simulation experiments on GAMMA 10 to investigate wave excitation, propagation and absorption. We observe the electron density fluctuations accompanied with the ICRF waves by using microwave reflectometer systems. It is confirmed that the wave of 6.36 MHz is further damped near the resonance layer in the internal region. The waves of 9.9 / 10.3 MHz excited in the east / west anchor cells interferes with the wave from the central cell. The interfered wave is controlled with antenna phasing by the phase difference between both antennas in the central and the anchor cell. The wave intensity measured by reflectometers depends clearly on the phase difference. In this talk, the availability of wave measurement with reflectometers is shown, and the wave propagation in the internal region of plasmas on GAMMA 10 is reported. This work is partly supported by JSPS, Japan (25400531, 15K17797) and by NIFS, Japan (NIFS15KUGM101).

  8. Monte Carlo simulation of initial breakdown phase for magnetised toroidal ICRF discharges

    SciTech Connect

    Tripský, M.; Van Oost, G.; Collaboration: ASDEX Upgrade Team; TEXTOR Team

    2014-02-12

    The radio-frequency (RF) plasma production technique in the ion cyclotron range of frequency (ICRF) attracts growing attention among fusion experts because of its high potential for solving several basic problems of reactor-oriented superconducting fusion machines, such as ICRF wall conditioning in tokamaks and stellarators (T{sub e} = 3−5eV, n{sub e}<10{sup 12}cm{sup −3}), ICRF-assisted tokamak start-up and target plasma production (n{sub e} = 10{sup 13}cm{sup −3}) in stellarators. Plasma initiation by ICRF has been studied intensively using single particle descriptions and basic analytic models. To further improve the present understanding on plasma production employing the vacuum RF field of ICRF antennas in toroidal devices in presence of the toroidal magnetic field, and its parametric dependencies a Monte Carlo code has been developed. The 1D code RFdinity1D describes the motion of electrons, accelerated by the RF field in front of the ICRF antenna, along one toroidal magnetic field line. Dependent on their individual energies and the related electron collision cross sections (ionisation, excitation and dissociation) weighted by a Monte Carlo procedure, an electron avalanche may occur. Breakdown conditions are discussed as function of RF discharge parameters (i) RF vacuum electric field strength, (ii) RF frequency and (iii) neutral pressure (H2). The slope of the exponential density increase, taken as measure for the breakdown speed, shows qualitative agreement to experimental breakdown times as found in literature and experimental data of the ASDEX upgrade and TEXTOR tokamak, and is interpreted by studying the characteristic electron velocity distribution functions.

  9. Global wave modeling of electron interactions with fast magnetosonic waves

    NASA Astrophysics Data System (ADS)

    Jaeger, E. F.; Batchelor, D. B.; Murakami, M.

    Electron interactions with fast magnetosonic waves are of interest for both direct electron heating and fast-wave current drive (FWCD) in tokamaks. Here the authors apply the full-wave ICRF code PICES to examples of both of these applications. To realistically account for the actual D-shaped magnetic geometry of present-day tokamaks, PICES is interfaced with the 3-D MHD equilibrium code VMEC. Likewise, to correctly model the real toroidal structure of both source and image currents in ICRF current drive antennas, PICES is interfaced with the 2-D recessed antenna impedance code RANT. Both current drive and electron heating by fast waves can be strongly altered through modification of the kappa(sub (parallel))-spectrum by the poloidal magnetic field. A poloidal mode expansion in PICES allows such variations in kappa(sub (parallel)) to be included correctly. In this paper, comparisons are made to observations of the direct electron heating profile on TFTR and to the FWCD efficiency on DIII-D. They also extrapolate to make predictions for future tokamaks such as TPX and ITER.

  10. Benchmarking ICRF simulations for ITER

    SciTech Connect

    R. V. Budny, L. Berry, R. Bilato, P. Bonoli, M. Brambilla, R.J. Dumont, A. Fukuyama, R. Harvey, E.F. Jaeger, E. Lerche, C.K. Phillips, V. Vdovin, J. Wright, and members of the ITPA-IOS

    2010-09-28

    Abstract Benchmarking of full-wave solvers for ICRF simulations is performed using plasma profiles and equilibria obtained from integrated self-consistent modeling predictions of four ITER plasmas. One is for a high performance baseline (5.3 T, 15 MA) DT H-mode plasma. The others are for half-field, half-current plasmas of interest for the pre-activation phase with bulk plasma ion species being either hydrogen or He4. The predicted profiles are used by seven groups to predict the ICRF electromagnetic fields and heating profiles. Approximate agreement is achieved for the predicted heating power partitions for the DT and He4 cases. Profiles of the heating powers and electromagnetic fields are compared.

  11. Potential Refinement of the ICRF

    NASA Technical Reports Server (NTRS)

    Ma, Chopo

    2003-01-01

    The analysis and data used for the ICRF represented the state of the art in global, extragalactic, X/S band microwave astrometry in 1995. The same general analysis method was used to extend the ICRF with subsequent VLBI data in a manner consistent with the original catalog. Since 1995 there have been considerable advances in the geodetic/astrometric VLBI data set and in the analysis that would significantly improve the systematic errors, stability, and density of the next realization of the ICRS when the decision is made to take this step. In particular, data acquired since 1990, including extensive use of the VLBA, are of higher quality and astrometric utility because of changes in instrumentation, schedule design, and networks as well as specifically astrometric intent. The IVS (International VLBI Service for Geodesy and Astrometry) continues to devote a portion of its observing capability to systematic extension of the astrometric data set. Sufficient data distribution exists to select a better set of defining sources. Improvements in troposphere modeling will minimize known systematic astrometric errors while accurate modeling and estimation of station effects from loading and nonlinear motions will permit the reintegration of the celestial reference frame, terrestrial reference frame and Earth orientation parameters though a single VLBI solution. The differences between the current ICRF and the potential next realization will be described.

  12. Potential Refinement of the ICRF

    NASA Astrophysics Data System (ADS)

    Ma, Chopo

    The ICRF analysis and data represented the state of the art in global extragalactic X/S band microwave astrometry in 1995. Similar analysis has been used to extend the ICRF with subsequent data consistent with the original catalog. Since 1995 there have been considerable advances in the geodetic/astrometric VLBI data set and analysis that would significantly improve the systematic errors stability and density of the next realization of the ICRS when the decision is made to take this step. In particular data acquired since 1990 including extensive use of the VLBA are of higher quality and astrometric utility because of changes in instrumentation schedule design and networks as well as specifically astrometric intent. The IVS (International VLBI Service for Geodesy and Astrometry) continues a systematic extension of the astrometric data set. Sufficient data distribution exists to select a better set of defining sources. Improvements in troposphere modeling will minimize known systematic astrometric errors while accurate modeling and estimation of station effects from loading and nonlinear motions should permit the reintegration of the celestial and terrestrial reference frames with Earth orientation parameters though a single VLBI solution. The differences between the current ICRF and the potential second realization will be described

  13. Potential refinement of the ICRF

    NASA Astrophysics Data System (ADS)

    Ma, Chopo

    2005-01-01

    The ICRF analysis and data represented the state of the art in global extragalactic X/S band microwave astrometry in 1995. Similar analysis has been used to extend the ICRF with subsequent data consistent with the original catalog. Since 1995 there have been considerable advances in the geodetic/astrometric VLBI data set and analysis that would significantly improve the systematic errors stability and density of the next realization of the ICRS when the decision is made to take this step. In particular data acquired since 1990 including extensive use of the VLBA are of higher quality and astrometric utility because of changes in instrumentation schedule design and networks as well as specifically astrometric intent. The IVS (International VLBI Service for Geodesy and Astrometry) continues a systematic extension of the astrometric data set. Sufficient data distribution exists to select a better set of defining sources. Improvements in troposphere modeling will minimize known systematic astrometric errors while accurate modeling and estimation of station effects from loading and nonlinear motions should permit the reintegration of the celestial and terrestrial reference frames with Earth orientation parameters though a single VLBI solution. The differences between the current ICRF and the potential second realization will be described.

  14. A DEMO relevant fast wave current drive high harmonic antenna exploiting the high impedance technique

    NASA Astrophysics Data System (ADS)

    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.

  15. A DEMO relevant fast wave current drive high harmonic antenna exploiting the high impedance technique

    SciTech Connect

    Milanesio, D. Maggiora, R.

    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.

  16. Progress in controlling ICRF-edge interactions in ASDEX upgrade

    NASA Astrophysics Data System (ADS)

    Bobkov, Vl.; Jacquet, Ph.; Ochoukov, R.; Zhang, W.; Bilato, R.; Braun, F.; Carralero, D.; Colas, L.; Czarnecka, A.; Dux, R.; Faugel, H.; Fünfgelder, H.; Jacquot, J.; Křivská, A.; Lunt, T.; Milanesio, D.; Maggiora, R.; Meyer, O.; Monakhov, I.; Noterdaeme, J.-M.; Potzel, S.; Pütterich, Th.; Stepanov, I.

    2015-12-01

    RF measurements during variation of the strap voltage balance of the original 2-strap ICRF antenna in ASDEX Upgrade at constant power are consistent with electromagnetic calculations by HFSS and TOPICA, more so for the latter. RF image current compensation is observed at the antenna limiters in the experiment at a local strap voltage of about half of the value of the remote strap, albeit with a non-negligible uncertainty in phasing. The RF-specific tungsten (W) source at the broad-limiter 2-strap antenna correlates strongly with the RF voltage at the local strap at the locations not connected to opposite side of the antenna along magnetic field lines. The trends of the observed increase of the RF loading with injection of local gas are well described by a combined EMC3-Eirene - FELICE calculations, with the most efficient improvement confirmed for the outer-midplane valves, but underestimated by about 1/3. The corresponding deuterium density tailoring is also likely responsible for the decrease of local W sources observed in the experiment.

  17. Progress in controlling ICRF-edge interactions in ASDEX upgrade

    SciTech Connect

    Bobkov, Vl. Ochoukov, R.; Bilato, R.; Braun, F.; Carralero, D.; Dux, R.; Faugel, H.; Fünfgelder, H.; Jacquot, J.; Lunt, T.; Potzel, S.; Pütterich, Th.; Jacquet, Ph.; Monakhov, I.; Zhang, W.; Noterdaeme, J.-M.; Stepanov, I.; Colas, L.; Meyer, O.; Czarnecka, A.; and others

    2015-12-10

    RF measurements during variation of the strap voltage balance of the original 2-strap ICRF antenna in ASDEX Upgrade at constant power are consistent with electromagnetic calculations by HFSS and TOPICA, more so for the latter. RF image current compensation is observed at the antenna limiters in the experiment at a local strap voltage of about half of the value of the remote strap, albeit with a non-negligible uncertainty in phasing. The RF-specific tungsten (W) source at the broad-limiter 2-strap antenna correlates strongly with the RF voltage at the local strap at the locations not connected to opposite side of the antenna along magnetic field lines. The trends of the observed increase of the RF loading with injection of local gas are well described by a combined EMC3-Eirene – FELICE calculations, with the most efficient improvement confirmed for the outer-midplane valves, but underestimated by about 1/3. The corresponding deuterium density tailoring is also likely responsible for the decrease of local W sources observed in the experiment.

  18. Generalized theory of ICRF convection and modeling of observed density profile modifications on TFTR

    SciTech Connect

    DIppolito, D.A.; Myra, J.R.; England, A.C.; Hanson, G.R.; Wilgen, J.B.; Rogers, J.H.; Majeski, R.; Schilling, G.; Wilson, J.R.; Hosea, J.C.

    1996-02-01

    Reflectometer measurements of the density profile in front of the TFTR Bay-K antenna as a function of antenna phasing and RF power provide a direct test of the theory of ICRF-driven convection. The data is shown to be qualitatively consistent with numerical calculations of the spatial distribution of the RF-sheath-driven {bold E}{times}{bold B} flow. A new picture of RF convection emerges from this work; the previous convective cell model is generalized to include enhanced particle loss caused by open streamlines intersecting the FS. {copyright} {ital 1996 American Institute of Physics.}

  19. The ICRF-3: Proposed Roadmap to the Next Generation International Celestial Reference Frame

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; Arias, F.; Boboltz, D.; Boehm, J.; Bolotin, S.; Bourda, G.; Charlot, P.; de Witt, A.; Fey, A.; Gaume, R.; Gordon, D.; Heinkelmann, R.; Lambert, S.; Ma, C.; Malkin, Z.; Nothnagel, A.; Seitz, M.; Skurikhina, E.; Souchay, J.; Titov, O.

    2013-09-01

    We propose a 3rd generation radio-based International Celestial Reference Frame (ICRF- 3) to improve upon the highly successful ICRF-2. Our goals are to improve the precision, spatial and frequency coverages relative to the ICRF-2 by 2018. This date is driven by the desire to create radio frames early enough to test the Gaia optical frame during its construction. Several specific actions are underway. A collaboration has been started to improve S/X-band precision of the 2000+ VLBA Calibrator Survey sources which are typically 5 times less precise than the rest of the ICRF-2. S/X-band southern precision improvements are planned from observations with southern antennas such as the AuScope and HartRAO, S. Africa. We seek to improve radio frequency coverage with X/Ka and K- band work. An X/Ka frame of 631 sources now has full sky coverage from the addition of a 2nd southern station in Argentina which should strengthen the southern hemisphere in general. A K-band collaboration has formed with similar coverage and southern precision goals. On the analysis front, special attention will be given to combination techniques both of VLBI catalogs and of multiple data types (e.g. VLBI+GPS). Finally, work is underway to identify and pinpoint sources bright enough in both radio and optical to allow for a robust frame tie between VLBI and Gaia optical frames.

  20. Generation of harmonic frequencies and their effects in present day ICRF systems

    NASA Astrophysics Data System (ADS)

    Durodié, F.; Vervier, M.

    1999-09-01

    The whole TEXTOR-94 ICRF system [1,2] circuit has been analyzed, partially modelled and studied at the fundamental operating frequency and, more important, at harmonic frequencies thereof. It has been found that without appropriate measures, present day systems and especially the TEXTOR ICRF system are prone to spurious generation of power at the second harmonic frequency. This leads either to erroneous activation of the reflected power safety protection or to highly increased (in some cases doubled) voltages in the transmission lines and antennas. As the voltage standing waves at the second harmonic displace the total voltage maxima in the transmission lines and antennas, this also explains why arcs are not always found at the expected voltage maxima for the fundamental frequency. The model is also able to give additional explanations why the ASDEX-Upgrade ICRF system has dramatically improved its power handling capabilities after the introduction of the ``3dB coupler reflection compensation scheme'' [3,4]. The output of one of the TEXTOR transmitters has been fitted with a quarter wave length shorted stub which has no effect on the operation at the fundamental frequency but which effectively shorts out the second harmonic. It has to be noted that eg. the Tore Supra RDL [5] antennas are fitted with such a stub in the feeding transmission line whose function is to enter cooling water into the transmission line system. Hence, this could be the explanation of the apparent higher than average power handling capabilities of the TS antenna system. Experimental results clearly indicate a much improved operational power handling capability on plasma and an increased voltage stand-off when conditioning this antenna pair on vacuum. Limits have yet to be explored but already remarkable is the fact that since the installation of the quarter wavelength stub the reflected power safety system has been activated only once and furthermore so in poorly matched conditions.

  1. Two frequency ICRF heating of D-T plasmas on TFTR

    SciTech Connect

    Rogers, J.H.; Majeski, R.; Wilson, J.R.; Hosea, J.C.; Schilling, G.; Stevens, J.; Ho, Y.L.; Raman, S.; Rasmussen, D.A.

    1993-11-01

    Modifications have been made to allow two of the ICRF antennas (bays L and M) on TFTR to operate at either of two frequencies, 43 MHz or 64 MHz. This was accomplished by lengthening the resonant loops feeding the antennas (2{lambda} at 43 MHz, 3{lambda} at 64 MHz) and replacing the conventional quarter wave impedance transformers with a tapered impedance design. The other two antennas (bays K and N) will operate at a fixed frequency, 43 MHz. The two frequency operation allows a combination of {sup 3}He-minority (or T second harmonic) and H-minority heating at full toroidal field on TFIR. Multiple frequency operation may also be useful in direct electron heating and current drive experiments. Other modifications have been made which are expected to permit arbitrary phasing between the current straps on bays M and L. The system design of the antenna, resonant loops and impedance matching system as well as preliminary TFTR results are discussed.

  2. Optical counterpart of ICRF: HIPPARCOS

    NASA Astrophysics Data System (ADS)

    Lindegren, L.; Perryman, M. A. C.

    The Hipparcos reference frame is defined by the positions and proper motions of nearly 118,000 stars given in the Hipparcos Catalogue. It is the optical counterpart of the International Celestial Reference Frame defined by the radio positions of extragalactic sources. The presentation gives a summary of the intrinsic properties of the Hipparcos reference frame, while its relation to the ICRF is discussed separately by J.~Kovalevsky. Median standard errors for stars brighter than 9~mag are around 0.8~mas in position at the catalogue epoch (J1991.25) and 0.9~ mas/yr in proper motion. The quality of the optical reference frame depends also on less easily quantified characteristics of the catalogue data, such as the uniformity and consistency of the astrometric data, the existence of temporal and spatial correlations, and the effects of unresolved binaries. The format of the Hipparcos Catalogue and its availability on different media are summarised.

  3. Recent Developments in High-Harmonic Fast Wave Physics in NSTX

    SciTech Connect

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

    2010-10-06

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

  4. A Fast MoM Solver (GIFFT) for Large Arrays of Microstrip and Cavity-Backed Antennas

    SciTech Connect

    Fasenfest, B J; Capolino, F; Wilton, D

    2005-02-02

    A straightforward numerical analysis of large arrays of arbitrary contour (and possibly missing elements) requires large memory storage and long computation times. Several techniques are currently under development to reduce this cost. One such technique is the GIFFT (Green's function interpolation and FFT) method discussed here that belongs to the class of fast solvers for large structures. This method uses a modification of the standard AIM approach [1] that takes into account the reusability properties of matrices that arise from identical array elements. If the array consists of planar conducting bodies, the array elements are meshed using standard subdomain basis functions, such as the RWG basis. The Green's function is then projected onto a sparse regular grid of separable interpolating polynomials. This grid can then be used in a 2D or 3D FFT to accelerate the matrix-vector product used in an iterative solver [2]. The method has been proven to greatly reduce solve time by speeding up the matrix-vector product computation. The GIFFT approach also reduces fill time and memory requirements, since only the near element interactions need to be calculated exactly. The present work extends GIFFT to layered material Green's functions and multiregion interactions via slots in ground planes. In addition, a preconditioner is implemented to greatly reduce the number of iterations required for a solution. The general scheme of the GIFFT method is reported in [2]; this contribution is limited to presenting new results for array antennas made of slot-excited patches and cavity-backed patch antennas.

  5. Fast-wave Power Flow Along SOL Field Lines In NSTX nd The Associated Power Deposition Profile Across The SOL In Front Of The Antenna

    SciTech Connect

    Perkins, Roy

    2013-06-21

    Fast-wave heating and current drive efficiencies can be reduced by a number of processes in the vicinity of the antenna and in the scrape off layer (SOL). On NSTX from around 25% to more than 60% of the high-harmonic fast-wave power can be lost to the SOL regions, and a large part of this lost power flows along SOL magnetic field lines and is deposited in bright spirals on the divertor floor and ceiling. We show that field-line mapping matches the location of heat deposition on the lower divertor, albeit with a portion of the heat outside of the predictions. The field-line mapping can then be used to partially reconstruct the profile of lost fast-wave power at the midplane in front of the antenna, and the losses peak close to the last closed flux surface (LCFS) as well as the antenna. This profile suggests a radial standing-wave pattern formed by fast-wave propagation in the SOL, and this hypothesis will be tested on NSTX-U. Advanced RF codes must reproduce these results so that such codes can be used to understand this edge loss and to minimize RF heat deposition and erosion in the divertor region on ITER.

  6. Extending the ICRF to Higher Radio Frequencies

    NASA Technical Reports Server (NTRS)

    Jacobs, C. S.; Jones, D. L.; Lanyi, G. E.; Lowe, S. T.; Naudet, C. J.; Resch, G. M.; Steppe, J. A.; Zhang, L. D.; Ulvestad, J. S.; Taylor, G. B.

    2002-01-01

    The ICRF forms the basis for all astrometry including use as the inertial coordinate system for navigating deep space missions. This frame was defined using S/X-band observations over the past 20+ years. In January 2002, the VLBA approved our proposal for observing time to extend the ICRF to K-band (24 GHz) and Q-band (43 GHz). The first step will be observations at K- and Q-bands on a subset of ICRF sources. Eventually, K- and Q-band multi-epoch observations will be used to estimate positions, flux density and source structure for a large fraction of the current S/X-band ICRF source list. This work will benefit the radio astronomy community by extending the VLBA calibrator list at these bands. In the longer term, we would also like to extend the ICRF to Ka-band (32 GHz). A celestial reference frame will be needed at this frequency to support deep space navigation. A navigation demonstration is being considered for NASA's Mars 2005 mission. The initial K- and Q-band work will serve to identify candidate sources at Ka-band for use with that mission.

  7. Modeling of ICRF Internal Transport Barrier Control for Advanced Tokamaks

    NASA Astrophysics Data System (ADS)

    Sund, R. S.; Scharer, J. E.

    1998-11-01

    We present an analysis of TFTR ICRF current drive experiments carried out by Majeski et al.(R. Majeski, J. Rodgers, G. Schilling, C. Phillips, J. Hosea and the TFTR Group, private communication.) The influence of deuterium, tritium, minority specie, electron and alpha concentrations, temperatures and beam fractions are considered for the two-ion mode conversion current drive experiments. Direct comparison with experimental data is carried out by means of a nonlocal large gyroradius ICRF code(O. Sauter, Ph.D. thesis, Ecole Polytechnique de Lausanne, Switzerland (1992).) which incorporates 1-D plasma profiles. It is found that substantial beam and alpha particle absorption can occur for some cases. Application of ion cyclotron range of frequencies internal transport barrier control requires further examination of fast wave mode conversion and the interaction of ion Bernstein waves with plasmas in advanced tokamaks. The effects of perpendicular and parallel magnetic gradients on the ion, electron, and alpha particle absorption are examined. A viable internal transport barrier control scheme for a reactor grade advanced tokamak will be discussed.

  8. Wave coupling in the magnetized plasma edge: Impact of a finite, inhomogeneous density inside the antenna box

    NASA Astrophysics Data System (ADS)

    Lu, L.; Crombé, K.; Van Eester, D.; Colas, L.; Jacquot, J.

    2015-12-01

    Most present Ion Cyclotron Resonant Frequency (ICRF) heating codes and antenna codes assume the antenna sitting in a vacuum region and consider the fast wave only, which implicitly performs an abrupt density transition from vacuum to above lower hybrid (LH) resonance. We studied the impact of densities that decay continuously inside the antenna box on near field patterns and power coupling. A new full wave code based on the COMSOL Finite Element Solver has been developed to investigate this topic. It is shown that: up to the memory limits of the adopted workstation, the local RF field pattern in low-density regions below the LH resonance changes with the grid size. Interestingly and importantly, however, the total coupled spectrum is independent to the mesh size and is weakly affected by the presence of the density profile inside the antenna box in dipole phasing. Thus one can drop out this density for coupling studies. Simulation also shows that varying the density gradient in the fast wave evanescence region has no significant effect on wave coupling.

  9. Next ICRF: Single global solution versus combination

    NASA Astrophysics Data System (ADS)

    Yatskiv, Yaroslav; Malkin, Zinovy

    2007-09-01

    Two approaches to generate the ICRF-2 are compared. The first approach, which has been used for the creation of the current ICRF realization, implies computation of the radio source positions in a single analysis center making use of the most advanced models, software and analysis strategy. However, the latter cannot guarantee that the reference frame is free of systematic errors. The second approach is based on combination of several CRF realizations after investigation and accounting for their stochastic and systematic errors. This procedure is intended to mitigate the systematic errors and improve the precision of the final combined solution. In this presentation, the advantages and shortcomings of both the approaches are discussed.

  10. Fast wave current drive experiment on the DIII-D tokamak

    SciTech Connect

    Petty, C.C.; Pinsker, R.I.; Chiu, S.C.; deGrassie, J.S.; Harvey, R.W.; Lohr, J.; Luce, T.C.; Mayberry, M.J.; Prater, R. ); Porkolab, M. ); Baity, F.W.; Goulding, R.H.; Hoffman, J.D. ); James, R.A. ); Kawash

    1992-06-01

    One method of radio-frequency heating which shows theoretical promise for both heating and current drive in tokamak plasmas is the direct absorption by electrons of the fast Alfven wave (FW). Electrons can directly absorb fast waves via electron Landau damping and transit-time magnetic pumping when the resonance condition {omega} {minus} {kappa}{sub {parallel}e}{upsilon}{sup {parallel}e} = O is satisfied. Since the FW accelerates electrons traveling the same toroidal direction as the wave, plasma current can be generated non-inductively by launching FW which propagate in one toroidal direction. Fast wave current drive (FWCD) is considered an attractive means of sustaining the plasma current in reactor-grade tokamaks due to teh potentially high current drive efficiency achievable and excellent penetration of the wave power to the high temperature plasma core. Ongoing experiments on the DIII-D tokamak are aimed at a demonstration of FWCD in the ion cyclotron range of frequencies (ICRF). Using frequencies in the ICRF avoids the possibility of mode conversion between the fast and slow wave branches which characterized early tokamak FWCD experiments in the lower hybrid range of frequencies. Previously on DIII-D, efficient direct electron heating by FW was found using symmetric (non-current drive) antenna phasing. However, high FWCD efficiencies are not expected due to the relatively low electron temperatures (compared to a reactor) in DIII-D.

  11. Experimental Investigation of RF Sheath Rectification in ICRF and LH Heated Plasmas on Alcator C-Mod

    SciTech Connect

    Ochoukov, R.; Whyte, D. G.; Faust, I.; LaBombard, B.; Lipschultz, B.; Meneghini, O.; Wallace, G.; Wukitch, S.; Myra, J.

    2011-12-23

    Radio frequency (RF) rectification of the plasma sheath is being actively studied on C-Mod as a likely mechanism that leads to prohibitively high molybdenum levels in the plasma core of ion cyclotron RF (ICRF) heated discharges. We installed emissive, ion sensitive, Langmuir, and 3-D B-dot probes to quantify the plasma potentials ({Phi}{sub P}) in ICRF and lower hybrid (LH) heated discharges. Two probe sets were mounted on fixed limiter surfaces and one set of probes was mounted on a reciprocating (along the major radius) probe. Initial results showed that RF rectification is strongly dependent on the local plasma density and not on the local RF fields. The RF sheaths had a threshold-like appearance at the local density of {approx}10{sup 16} m-{sup 3}. Radial probe scans revealed that the RF sheaths peaked in the vicinity of the ICRF limiter surface, agreeing with a recent theory. The highest {Phi}{sub P}'s were observed on magnetic field lines directly mapped to the active ICRF antenna. Measurements in LH heated plasmas showed a strong {Phi}{sub P} dependence on the parallel index of refraction n{sub ||} of the launched LH waves: {Phi}{sub P} is greater at lower n{sub ||}. Little dependence was observed on the local plasma density.

  12. Application of Model Based Parameter Estimation for Fast Frequency Response Calculations of Input Characteristics of Cavity-Backed Aperture Antennas Using Hybrid FEM/MoM Technique

    NASA Technical Reports Server (NTRS)

    Reddy C. J.

    1998-01-01

    Model Based Parameter Estimation (MBPE) is presented in conjunction with the hybrid Finite Element Method (FEM)/Method of Moments (MoM) technique for fast computation of the input characteristics of cavity-backed aperture antennas over a frequency range. The hybrid FENI/MoM technique is used to form an integro-partial- differential equation to compute the electric field distribution of a cavity-backed aperture antenna. In MBPE, the electric field is expanded in a rational function of two polynomials. The coefficients of the rational function are obtained using the frequency derivatives of the integro-partial-differential equation formed by the hybrid FEM/ MoM technique. Using the rational function approximation, the electric field is obtained over a frequency range. Using the electric field at different frequencies, the input characteristics of the antenna are obtained over a wide frequency range. Numerical results for an open coaxial line, probe-fed coaxial cavity and cavity-backed microstrip patch antennas are presented. Good agreement between MBPE and the solutions over individual frequencies is observed.

  13. Nuclear analysis for the intor array of loops ICRF launcher module design

    SciTech Connect

    Sawan, M.E.

    1985-07-01

    Nuclear analysis for the array of loops ICRF launcher module design of INTOR is presented. The nuclear radiation environment in the different module components is determined. The fast neutron fluence in the BeO radome is 10/sup 22/ n/cm/sup 2/ after one full power year leading to significant microcracking. Activation calculations for SF/sub 6/ imply a total activity of 5 x 10/sup 4/ Ci at shutdown. Nuclear heating results in a large breakdown rate in SF/sub 6/. A 1.6 m thick nuclear shield is needed to allow for hands-on maintenance one day after shutdown behind the launcher module. The results imply that significant design changes are required for the array of loops ICRF launcher module to stand the severe INTOR nuclear environment.

  14. Ion cyclotron wave coupling in the magnetized plasma edge of tokamaks: impact of a finite, inhomogeneous density inside the antenna box

    NASA Astrophysics Data System (ADS)

    Lu, L.; Crombé, K.; Van Eester, D.; Colas, L.; Jacquot, J.; Heuraux, S.

    2016-05-01

    Most present ion cyclotron resonant frequency (ICRF) heating codes and antenna codes assume the antenna sitting in a vacuum region and consider the fast wave only, which implicitly performs an abrupt density transition from vacuum to above lower hybrid (LH) resonance. The impact of the appearance of the LH resonance is entirely overlooked in their simulations. We studied the impact of densities that decay continuously inside the antenna box on near field patterns and power coupling. A new full wave code based on the COMSOL Finite Element Solver has been developed to investigate this topic. It is shown that: up to the memory limits of the adopted workstation, the local RF field pattern in low-density regions below the LH resonance changes with the grid size. Interestingly and importantly, however, the total coupled toroidal spectrum is almost independent on the mesh size and is weakly affected by the presence of the density profile inside the antenna box in dipole toroidal strap phasing. This suggests one can drop out this density for coupling studies to speed up the computation. Simulation also shows that varying the density gradient in the fast wave evanescence region has no significant effect on wave coupling.

  15. The analysis of complex antenna structures (like the ITER array) using TOPICA

    NASA Astrophysics Data System (ADS)

    Maggiora, R.; Milanesio, D.; Lancellotti, V.; Meneghini, O.; Vecchi, G.

    2007-09-01

    TOPICA (Torino Polytechnic Ion Cyclotron Antenna) code is an innovative tool for the 3D/1D simulation of Ion Cyclotron Radio Frequency (ICRF) antennas, i.e. accounting for realistic 3D antenna geometries and for accurate 1D plasma models. The tool calculates the antenna input parameters at the feeding ports given the exact port excitation. Moreover, it calculates the current distribution and electric field maps wherever specified. The recent upgraded parallelized version of TOPICA permits the analysis of large and complex antenna structures in a reasonable simulation time (less than one day). A detailed analysis of the performances of two ITER ICRF antenna geometries has been carried out, underlining the strong dependence and the asymmetries of the antenna input parameters due to plasma conditions. An optimization of the antenna dimensions has also been accomplished. Electric current distribution on conductors in the vacuum region and electric field distribution in the vacuum region and at the interface with plasma edge have been calculated as well. The analysis shows the strong capabilities of the parallelized TOPICA code as a predictive tool and its usefulness to ICRF antennas final design.

  16. Measurement and simulation of ICRF wave intensity with a recalibrated phase contrast imaging diagnostic on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Tsujii, N.; Porkolab, M.; Bonoli, P. T.; Edlund, E. M.; Ennever, P. C.; Lin, Y.; Wright, J. C.; Wukitch, S. J.; Jaeger, E. F.; Green, D. L.; Harvey, R. W.

    2015-12-01

    Waves in the ion cyclotron range of frequencies (ICRF) are one of the major tools to heat fusion plasmas. Full-wave simulations are essential to predict the wave propagation and absorption quantitatively, and it is important that these codes be validated against actual experimental measurements. In this work, the absolute intensity of the ICRF waves previously measured with a phase contrast imaging diagnostic was recalibrated and compared once more with full-wave predictions. In the earlier work, significant discrepancies were found between the measured and the simulated mode converted wave intensity [N. Tsujii et al., Phys. Plasmas 19, 082508]. With the new calibration of the detector array, the measured mode converted wave intensity is now in much better agreement with the full-wave predictions. The agreement is especially good for comparisons performed close to the antenna.

  17. Measurement and simulation of ICRF wave intensity with a recalibrated phase contrast imaging diagnostic on Alcator C-Mod

    SciTech Connect

    Tsujii, N.; Porkolab, M.; Bonoli, P. T.; Edlund, E. M.; Ennever, P. C.; Lin, Y.; Wright, J. C.; Wukitch, S. J.; Jaeger, E. F.; Green, D. L.; Harvey, R. W.

    2015-12-10

    Waves in the ion cyclotron range of frequencies (ICRF) are one of the major tools to heat fusion plasmas. Full-wave simulations are essential to predict the wave propagation and absorption quantitatively, and it is important that these codes be validated against actual experimental measurements. In this work, the absolute intensity of the ICRF waves previously measured with a phase contrast imaging diagnostic was recalibrated and compared once more with full-wave predictions. In the earlier work, significant discrepancies were found between the measured and the simulated mode converted wave intensity [N. Tsujii et al., Phys. Plasmas 19, 082508]. With the new calibration of the detector array, the measured mode converted wave intensity is now in much better agreement with the full-wave predictions. The agreement is especially good for comparisons performed close to the antenna.

  18. Maximization of ICRF power by SOL density tailoring with local gas injection

    NASA Astrophysics Data System (ADS)

    Jacquet, P.; Goniche, M.; Bobkov, V.; Lerche, E.; Pinsker, R. I.; Pitts, R. A.; Zhang, W.; Colas, L.; Hosea, J.; Moriyama, S.; Wang, S.-J.; Wukitch, S.; Zhang, X.; Bilato, R.; Bufferand, H.; Guimarais, L.; Faugel, H.; Hanson, G. R.; Kocan, M.; Monakhov, I.; Noterdaeme, J.-M.; Petrzilka, V.; Shaw, A.; Stepanov, I.; Sips, A. C. C.; Van Eester, D.; Wauters, T.; JET contributors, the; the ASDEX Upgrade Team; the DIII-D Team; ITPA ‘Integrated Operation Scenarios' members, the; experts

    2016-04-01

    Experiments have been performed under the coordination of the International Tokamak Physics Activity (ITPA) on several tokamaks, including ASDEX Upgrade (AUG), JET and DIII-D, to characterize the increased Ion cyclotron range of frequency (ICRF) antenna loading achieved by optimizing the position of gas injection relative to the RF antennas. On DIII-D, AUG and JET (with the ITER-Like Wall) a 50% increase in the antenna loading was observed when injecting deuterium in ELMy H-mode plasmas using mid-plane inlets close to the powered antennas instead of divertor injection and, with smaller improvement when using gas inlets located at the top of the machine. The gas injection rate required for such improvements (~0.7  ×  1022 el s-1 in AUG, ~1.0  ×  1022 el s-1 in JET) is compatible with the use of this technique to optimize ICRF heating during the development of plasma scenarios and no degradation of confinement was observed when using the mid-plane or top inlets compared with divertor valves. An increase in the scrape-off layer (SOL) density was measured when switching gas injection from divertor to outer mid-plane or top. On JET and DIII-D, the measured SOL density increase when using main chamber puffing is consistent with the antenna coupling resistance increase provided that the distance between the measurement lines of sight and the injection location is taken into account. Optimized gas injection was also found to be beneficial for reducing tungsten (W) sputtering at the AUG antenna limiters, and also to reduce slightly the W and nickel (Ni) content in JET plasmas. Modeling the specific effects of divertor/top/mid-plane injection on the outer mid-plane density was carried out using both the EDGE2D-EIRENE and EMC3-EIRENE plasma boundary code packages; simulations indeed indicate that outer mid-plane gas injection maximizes the density in the mid-plane close to the injection point with qualitative agreement with the AUG SOL density measurements

  19. Observations of neutral beam and ICRF tail ion losses due to Alfven modes in TFTR

    SciTech Connect

    Darrow, D.S.; Zweben, S.J.; Chang, Z.

    1996-04-01

    Fast ion losses resulting from MHD modes at the Alfven frequency, such as the TAE, have been observed in TFTR. The modes have been driven both by neutral beam ions, at low B{sub T}, and by H-minority ICRF tail ions at higher B{sub T}. The measurements indicate that the loss rate varies linearly with the mode amplitude, and that the fast ion losses during the mode activity can be significant, e.g. up to 10% of the input power is lost in the worst case.

  20. The ICRF now and in the future

    NASA Astrophysics Data System (ADS)

    Charlot, P.; Bourda, G.

    The current realization of the International Celestial Reference Frame - the ICRF2, in use since January 1, 2010 - includes positions for a total of 3414 extragalactic sources with a noise floor of 40 mu as in the individual source coordinates. The ICRF2 positions were determined from measurements acquired at 8.4 and 2.3 GHz with Very Long Baseline Interferometry (VLBI) over the past 30 years. The frame is constantly improving through joint observational efforts of the VLBI community and by taking advantage of the latest refinements in modeling and data acquisition technology, all of which aim at a denser and more accurate celestial frame. Specific work is targeted towards finding the most compact sources, identifying those that are also bright at optical wavelengths and extending the frame at higher radio frequencies. This paper reviews progress in these areas and draws prospects for aligning the VLBI frame with the future Gaia optical frame in the next decade.

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

    SciTech Connect

    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.

  2. Rotating field antenna experiments in Phaedrus-B

    NASA Astrophysics Data System (ADS)

    Yasaka, Y.; Majeski, R.; Browning, J.; Hershkowitz, N.; Roberts, D.

    1987-09-01

    The rotating field antenna installed in the central cell of the Phaedrus-B tandem mirror consists of two close-spaced dual half-turn ICRF antennas. The symmetry axes of the antennas are rotated 90° with respect to each other. Each antenna is driven by a separate rf amplifier, with ≳200 KW power output. The polarization of the resultant antenna near fields is selected by the relative phasing of the antenna currents. In particular, the antenna set can produce nearly pure left or right circularly polarized fields. We find an increase in ion heating as the field polarization is varied from right circularly polarized through linear polarization to left circular polarization, for plasma densities up to 3-4×1012 cm-3, when the antenna set is driven at ω˜ωci (midplane). Ion temperature is diagnosed by a time of flight neutral energy analyzer. Results are compared to the predictions of the ICRF code ANTENA of Brian McVey.

  3. Active and fast particle driven Alfvén eigenmodes in Alcator C-Moda)

    NASA Astrophysics Data System (ADS)

    Snipes, J. A.; Basse, N.; Boswell, C.; Edlund, E.; Fasoli, A.; Gorelenkov, N. N.; Granetz, R. S.; Lin, L.; Lin, Y.; Parker, R.; Porkolab, M.; Sears, J.; Sharapov, S.; Tang, V.; Wukitch, S.

    2005-05-01

    Alfvén eigenmodes (AEs) are studied to assess their stability in high density reactor relevant regimes where Ti≈Te and as a diagnostic tool. Stable AEs are excited with active magnetohydrodynamics antennas in the range of the expected AE frequency. Toroidal Alfvén eigenmode (TAE) damping rates between 0.5%<γ/ω<4.5% have been observed in diverted and limited Ohmic plasmas. Unstable AEs are excited with a fast ion tail driven by H minority ion cyclotron radio frequency (ICRF) heating with electron densities in the range of n¯e=0.5-2×1020m-3. Energetic particle modes or TAEs have been observed to decrease in frequency and mode number with time up to a large sawtooth collapse, indicating the role fast particles play in stabilizing sawteeth. In the current rise phase, unstable modes with frequencies that increase rapidly with time are observed with magnetic pick-up coils at the wall and phase contrast imaging density fluctuation measurements in the core. Modeling of these modes constrains the calculated safety factor profile to be very flat or with slightly reversed shear. AEs are found to be more stable for an inboard than for central or outboard ICRF resonances in qualitative agreement with modeling.

  4. Slow Wave Excitation in the ICRF and HHFW Regimes

    SciTech Connect

    Phillips, C. K.; Valeo, E. J.; Hosea, J. C.; LeBlanc, B. P.; Wilson, J. R.; Jaeger, E. F.; Berry, L. A.; Ryan, P. M.; Bonoli, P. T.; Wright, J. C.; Smithe, D. N.

    2011-12-23

    Theoretical considerations and high spatial resolution numerical simulations of radio frequency (rf) wave heating in tokamaks and in spherical toruses (ST) indicate that fast waves launched into tokamaks in the ion cyclotron range of frequencies (ICRF) or into spherical toruses in the high harmonic fast wave (HHFW) regime may excite a short wavelength slow mode inside of the plasma discharge due to the presence of hot electrons that satisfy the condition {omega}

  5. The ICRF-3: Status, Plans, and Multi-wavelength Progress on the next generation Celestial Reference Frame.

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher

    2015-08-01

    ICRF-3 seeks to improve upon the highly successful ICRF-2. Our goals are to improve the precision, spatial and frequency coverage relative to the ICRF-2 by 2018. This date is driven by the desire to create radio frames that are ready for comparison with the Gaia optical frame.Several specific actions are underway. A collaboration to improve at S/X-band precision of the Very Long Baseline Array (VLBA) Calibrator Survey's ~2200 sources, which are typically 5 times less precise than the rest of the ICRF-2, is bearing fruit and is projected to yield a factor of 3 improvement in precision. S/X-band southern hemisphere precision improvements are underway with observations using southern antennas such as the AuScope, Warkworth, and HartRAO, South Africa.We also seek to improve radio frequency coverage with X/Ka-band and K-band work. An X/Ka frame of 660 sources now has full sky coverage from the addition of a 2nd southern station in Argentina which is strengthening the southern hemisphere in general. The X/Ka-band frame's precision is now comparable to the ICRF-2 for the 530 sources in common. A K-band collaboration has formed with similar coverage and southern precision goals. By the time of this meeting, we expect K-band to complete full sky coverage with south polar cap observations and to improve spatial density north of -30 deg declination with VLBA observations.On the analysis front, special attention is being given to combination techniques both of Very Long Baseline Interferometry (VLBI) frames and of multiple data types. Consistency of the Celestial Reference Frame (CRF) with the Terrestrial Reference Frame (TRF) and Earth Oreintation Parameters (EOP) is another area of concern. Comparison of celestial frame solutions from various groups is underway in order to identify and correct systematic errors. We will discuss evidence emerging for 100 µas zonal errors in the ICRF2 in the declination range from 0 to -30 deg.Finally, work is underway to identify and

  6. Spectral effects on fast wave core heating and current drive

    SciTech Connect

    Phillips, Cynthia; Bell, R. E.; Berry, Lee; Jaeger, Erwin Frederick; Ryan, Philip Michael; Wilgen, John B

    2009-01-01

    Recent results obtained with high harmonic fast wave (HHFW) heating and current drive (CD) on NSTX strongly support the hypothesis that the onset of perpendicular fast wave propagation right at or very near the launcher is a primary cause for a reduction in core heating efficiency at long wavelengths that is also observed in ICRF heating experiments in numerous tokamaks. A dramatic increase in core heating efficiency was first achieved in NSTX L-mode helium majority plasmas when the onset for perpendicular wave propagation was moved away from the antenna and nearby vessel structures. Efficient core heating in deuterium majority L-mode and H-mode discharges, in which the edge density is typically higher than in comparable helium majority plasmas, was then accomplished by reducing the edge density in front of the launcher with lithium conditioning and avoiding operational points prone to instabilities. These results indicate that careful tailoring of the edge density profiles in ITER should be considered to limit radio frequency (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 HHFW CD 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.

  7. Simulation of High Power ICRF Wave Heating in the ITER Burning Plasma

    NASA Astrophysics Data System (ADS)

    Jaeger, E. F.; Berry, L. A.; Barrett, R. F.; D'Azevedo, E. F.

    2007-11-01

    ITER relies on Ion-cyclotron Radio Frequency (ICRF) power to heat the plasma to fusion temperatures. To heat effectively, the waves must couple efficiently to the core plasma. Recent simulations using AORSA [1] on the 120 TF Cray XT-4 (Jaguar) at ORNL show that the waves propagate radially inward and are rapidly absorbed with little heating of the plasma edge. AORSA has achieved 87.5 trillion calculations per second (87.5 teraflops) on Jaguar, which is 73 percent of the system's theoretical peak. Three dimensional visualizations show ``hot spots'' near the antenna surface where the wave amplitude is high. AORSA simulations are also being used to study how to best use ICRF to drive plasma currents for optimizing ITER performance and pulse length. Results for Scenario 4 show a maximum current of 0.54 MA for 20 MW of power at 57 MHz. [1] E.F. Jaeger, L.A. Berry, E. D'Azevedo, et al., Phys. Plasmas. 8, 1573 (2001).

  8. ICRF-induced DD fusion product losses in TFTR

    SciTech Connect

    Darrow, D.S.; Zweben, S.J.; Budny, R.V.

    1994-10-01

    When ICRF power is applied to TFTR plasmas in which there is no externally-supplied minority species, an enhanced loss of DD fusion products results. The characteristics of the loss are consistent with particles at or near the birth energy having their perpendicular velocity increased by the ICRF such that those near the passing/trapped boundary are carried into the first orbit loss cone. A rudimentary model of this process predicts losses of a magnitude similar to those seen. Extrapolations based upon this data for hypothetical ICRF ash removal from reactor plasmas suggest that the technique will not be energy efficient.

  9. The Second International Celestial Reference Frame (ICRF2)

    NASA Technical Reports Server (NTRS)

    Ma, Chopo

    2010-01-01

    The ICRF2 catalog was constructed by the IERS/IVS Working Group with oversight by the IAU Working Group. Derived using data from August 1979 through March 2009, it is a great improvement over the original ICRF with 3414 extragalactic radio source positions, a noise floor of 40 microarcsec, and axis stability of 10 microarcsec. Significant refinements were made in the selection of defining sources, modeling, and the integration of CRF, TRF, and EOP. The adoption of the ICRF2 was approved by the IAU in Resolution B3 at the XXVII IAU General Assembly and became effective 1 January 2010.

  10. Characterization and performance of a field aligned ion cyclotron range of frequency antenna in Alcator C-Moda)

    NASA Astrophysics Data System (ADS)

    Wukitch, S. J.; Garrett, M. L.; Ochoukov, R.; Terry, J. L.; Hubbard, A.; Labombard, B.; Lau, C.; Lin, Y.; Lipschultz, B.; Miller, D.; Reinke, M. L.; Whyte, D.; Alcator C-Mod Team

    2013-05-01

    Ion cyclotron range of frequency (ICRF) heating is expected to provide auxiliary heating for ITER and future fusion reactors where high Z metallic plasma facing components (PFCs) are being considered. Impurity contamination linked to ICRF antenna operation remains a major challenge particularly for devices with high Z metallic PFCs. Here, we report on an experimental investigation to test whether a field aligned (FA) antenna can reduce impurity contamination and impurity sources. We compare the modification of the scrape of layer (SOL) plasma potential of the FA antenna to a conventional, toroidally aligned (TA) antenna, in order to explore the underlying physics governing impurity contamination linked to ICRF heating. The FA antenna is a 4-strap ICRF antenna where the current straps and antenna enclosure sides are perpendicular to the total magnetic field while the Faraday screen rods are parallel to the total magnetic field. In principle, alignment with respect to the total magnetic field minimizes integrated E|| (electric field along a magnetic field line) via symmetry. A finite element method RF antenna model coupled to a cold plasma model verifies that the integrated E|| should be reduced for all antenna phases. Monopole phasing in particular is expected to have the lowest integrated E||. Consistent with expectations, we observed that the impurity contamination and impurity source at the FA antenna are reduced compared to the TA antenna. In both L and H-mode discharges, the radiated power is 20%-30% lower for a FA-antenna heated discharge than a discharge heated with the TA-antennas. However, inconsistent with expectations, we observe RF induced plasma potentials (via gas-puff imaging and emissive probes to be nearly identical for FA and TA antennas when operated in dipole phasing). Moreover, the highest levels of RF-induced plasma potentials are observed using monopole phasing with the FA antenna. Thus, while impurity contamination and sources are indeed

  11. Characterization and performance of a field aligned ion cyclotron range of frequency antenna in Alcator C-Mod

    SciTech Connect

    Wukitch, S. J.; Garrett, M. L.; Ochoukov, R.; Terry, J. L.; Hubbard, A.; Labombard, B.; Lau, C.; Lin, Y.; Lipschultz, B.; Miller, D.; Reinke, M. L.; Whyte, D.; Collaboration: Alcator C-Mod Team

    2013-05-15

    Ion cyclotron range of frequency (ICRF) heating is expected to provide auxiliary heating for ITER and future fusion reactors where high Z metallic plasma facing components (PFCs) are being considered. Impurity contamination linked to ICRF antenna operation remains a major challenge particularly for devices with high Z metallic PFCs. Here, we report on an experimental investigation to test whether a field aligned (FA) antenna can reduce impurity contamination and impurity sources. We compare the modification of the scrape of layer (SOL) plasma potential of the FA antenna to a conventional, toroidally aligned (TA) antenna, in order to explore the underlying physics governing impurity contamination linked to ICRF heating. The FA antenna is a 4-strap ICRF antenna where the current straps and antenna enclosure sides are perpendicular to the total magnetic field while the Faraday screen rods are parallel to the total magnetic field. In principle, alignment with respect to the total magnetic field minimizes integrated E|| (electric field along a magnetic field line) via symmetry. A finite element method RF antenna model coupled to a cold plasma model verifies that the integrated E|| should be reduced for all antenna phases. Monopole phasing in particular is expected to have the lowest integrated E||. Consistent with expectations, we observed that the impurity contamination and impurity source at the FA antenna are reduced compared to the TA antenna. In both L and H-mode discharges, the radiated power is 20%–30% lower for a FA-antenna heated discharge than a discharge heated with the TA-antennas. However, inconsistent with expectations, we observe RF induced plasma potentials (via gas-puff imaging and emissive probes to be nearly identical for FA and TA antennas when operated in dipole phasing). Moreover, the highest levels of RF-induced plasma potentials are observed using monopole phasing with the FA antenna. Thus, while impurity contamination and sources are indeed

  12. Resonant loop antenna design with a 2-D steady state analysis

    SciTech Connect

    Chen, G.I.; Ryan, P.M.; Hoffman, D.J.; Baity, F.W.; Swain, D.W.; Whealton, J.H.

    1987-01-01

    Evaluation of resonant loop antenna designs for ICRF heating of plasmas requires information concerning the electrical characteristics of the structure. Our 2-D steady state model described herein provides us with current strap inductance and capacitance, surface current distributions, and flux linkage to the plasma. These are used to determine the current and voltage requirements, ohmic dissipation, frequency limits and matching requirements, maximum electric fields, and plasma loading in order to compare antenna designs.

  13. ICRF sawtooth stabilization: Application on TFTR and CIT

    SciTech Connect

    Hosea, J.C.; Phillips, C.K.; Stevens, J.E.; Wilson, J.R.; Bell, M.; Boivin, R.; Cavallo, A.; Colestock, P.; Fredrickson, E.; Hammett, G.; Hsuan, H.; Janos, A.; Jassby, D.; Jobes, F.; McGuire, K.; Mueller, D.; Nagayama, Y.; Owens, K.; Park, H.; Schmidt, G.; Stratton, B.; Taylor, G.; Wong, K.L.; Zweben, S. . Plasma Physics Lab.); Hoffman, D. )

    1991-03-01

    The use of ICRF heating to stabilize the core plasma sawtooth relaxations has been extended to TFTR where such stabilization has been produced at relatively low power in the L Mode regime at moderate density (P{sub RF} = 4 MW, 2.6 MW in helium and deuterium discharges, respectively, for the minority hydrogen ICRF heating regime with {bar n}{sub e}{approx}2.5 {times} 10{sup 13} cm{sup {minus}3}). These results, as in the case of those obtained on JET, are qualitatively consistent with energetic ion stabilization of the m = 1, n = 1 ideal/resistive kink mode. The relevance of sawtooth stabilization to the primary regimes of interest on TFTR -- the high-Q supershot regime and the high density pellet injection regimes -- and on CIT -- the high density ICRF heated regime -- is considered in the context of the present theory and the projected ICRF power deposition characteristics. 35 refs., 11 figs.

  14. Aircraft antennas/conformal antennas missile antennas

    NASA Astrophysics Data System (ADS)

    Solbach, Klaus

    1987-04-01

    Three major areas of airborne microwave antennas are examined. The basic system environment for missile telemetry/telecommand and fuze functions is sketched and the basic antenna design together with practical examples are discussed. The principle requirements of modern nose radar flat plate antennas are shown to result from missile/aircraft system requirements. Basic principles of slotted waveguide antenna arrays are sketched and practical antenna designs are discussed. The present early warning system designs are sketched to point out requirements and performance of practical radar warning and jamming antennas (broadband spiral antennas and horn radiators). With respect to newer developments in the ECM scenario, some demonstrated and proposed antenna systems (lens fed arrays, phased array, active array) are discussed.

  15. Folded waveguide cavity coupler for ICRF heating

    SciTech Connect

    Owens, T.L.

    1986-01-01

    This paper introduces a new type of waveguide coupler for ion cyclotron range of frequencies (ICRF) heating which is an adaptation of a concept known as a ''folded waveguide'' reported by Barrow and Schaevitz in connection with low-frequency waveguide transmission systems. The basic idea involves ''folding'' a simple rectangular waveguide to form a more compact structure. Cutoff for the folded waveguide occurs when one-half of a free-space wavelength equals the path length around the ''folds'' of the structure. By adding a large number of folds, the path length around the folds can be made large, leading to very low cutoff frequencies relative to those for simple rectangular waveguides having comparable outside dimensions. Folded waveguide couplers are practical for frequencies as low as 60 MHz for some ports found on present-day experients.

  16. The IAU Division A Working Group on the Third Realization of the ICRF: Background, Goals, Plans

    NASA Astrophysics Data System (ADS)

    Gaume, Ralph

    2015-08-01

    The XXVIII General Assembly of the IAU (Beijing, 2012) established the Division A Working Group on the Third Realization of the International Celestial Reference Frame (ICRF). The adopted charter of the ICRF3 Working Group includes a commitment to report on the implementation and execution plans for ICRF3 during the XXIX General Assembly of the IAU along with a targeted completion and presentation of ICRF3 in 2018 to the XXX General Assembly for adoption. This talk will discuss the background, purpose, and overall implementation plan for ICRF3, and motivate the concept, currently under consideration by the ICRF3 Working Group, that future realizations of the ICRF be based on multi-frequency astrometric data, starting with ICRF3.

  17. Toroidal rotation induced by asymmetric cyclotron resonance absorption in minority ICRF-heated tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Wang, S.; Zhang, D.

    2016-04-01

    A new mechanism of ion cyclotron range of frequency (ICRF)-induced rotation is proposed to explain the toroidal rotation with minority ICRF heating without net momentum injection. For ICRF waves launched with the symmetric spectrum, a nonlinear toroidal force can be generated through the asymmetric absorption of the toroidal wave momentum, which is due to the finite toroidal rotation of minority ions. This ICRF-induced toroidal force can drive a significant toroidal rotation of bulk ions.

  18. Fast wave power flow along SOL field lines in NSTX

    NASA Astrophysics Data System (ADS)

    Perkins, R. J.; Bell, R. E.; Diallo, A.; Gerhardt, S.; Hosea, J. C.; Jaworski, M. A.; Leblanc, B. P.; Kramer, G. J.; Phillips, C. K.; Roquemore, L.; Taylor, G.; Wilson, J. R.; Ahn, J.-W.; Gray, T. K.; Green, D. L.; McLean, A.; Maingi, R.; Ryan, P. M.; Jaeger, E. F.; Sabbagh, S.

    2012-10-01

    On NSTX, a major loss of high-harmonic fast wave (HHFW) power can occur along open field lines passing in front of the antenna over the width of the scrape-off layer (SOL). Up to 60% of the RF power can be lost and at least partially deposited in bright spirals on the divertor floor and ceiling [1,2]. The flow of HHFW power from the antenna region to the divertor is mostly aligned along the SOL magnetic field [3], which explains the pattern of heat deposition as measured with infrared (IR) cameras. By tracing field lines from the divertor back to the midplane, the IR data can be used to estimate the profile of HHFW power coupled to SOL field lines. We hypothesize that surface waves are being excited in the SOL, and these results should benchmark advanced simulations of the RF power deposition in the SOL (e.g., [4]). Minimizing this loss is critical optimal high-power long-pulse ICRF heating on ITER while guarding against excessive divertor erosion.[4pt] [1] J.C. Hosea et al., AIP Conf Proceedings 1187 (2009) 105. [0pt] [2] G. Taylor et al., Phys. Plasmas 17 (2010) 056114. [0pt] [3] R.J. Perkins et al., to appear in Phys. Rev. Lett. [0pt] [4] D.L. Green et al., Phys. Rev. Lett. 107 (2011) 145001.

  19. VizieR Online Data Catalog: International Celestial Reference Frame 2, ICRF2 (Ma+, 2009)

    NASA Astrophysics Data System (ADS)

    Ma, C.; Arias, F. E.; Bianco, G.; Boboltz, D. A.; Bolotin, S. L.; Charlot, P.; Engelhardt, G.; Fey, A. L.; Gaume, R. A.; Gontier, A.-M.; Heinkelmann, R.; Jacobs, C. S.; Kurdubov, S.; Lambert, S. B.; Malkin, Z. M.; Nothnagel, A.; Petrov, L.; Skurikhina, E.; Sokolova, J. R.; Souchay, J.; Sovers, O. J.; Tesmer, V.; Titov, O. A.; Wang, G.; Zharov, V. E.; Barache, C.; Bockmann, S.; Collioud, A.; Gipson, J. M.; Gordon, D.; Lytvyn, S. O.; MacMillan, D. S.; Ojha, R.; Fey, A. L.; Gordon, D.; Jacobs, C. S.

    2013-06-01

    This Technical Note describes the generation by an international team of the second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years of Very Long Baseline Interferometry (VLBI) observations. ICRF2 contains precise positions of 3414 compact radio astronomical sources, more than five times the number as in the first ICRF, hereafter ICRF1. Further, the ICRF2 is found to have a noise floor of only 40μas, some 5-6 times better than ICRF1, and an axis stability of 10μas, nearly twice as stable as ICRF1. Alignment of ICRF2 with the International Celestial Reference System (ICRS) was made using 138 stable sources common to both ICRF2 and ICRF1-Ext2. Future maintenance of ICRF2 will be made using a set of 295 new "defining" sources selected on the basis of positional stability and the lack of extensive intrinsic source structure. The stability of these 295 defining sources, and their more uniform sky distribution eliminates the two largest weaknesses of ICRF1. (2 data files).

  20. Analysis And Design Of Antennas Facing Cylindrical Plasma Columns With TOPCYL

    NASA Astrophysics Data System (ADS)

    Guadamuz, S.; Graswinckel, M. F.; Koch, R.; Maggiora, R.; Van De Pol, M.; Vietti, G.; Van Rooij, G.

    2011-12-01

    On recent years TOPICA[1] has shown its capabilities as a designing tool for ICRF antennas on tokamaks, handling both the realistic geometrical detail of the structure as well as a complete description of the plasma region behavior. Now, expanding these capabilities, the TOrino Polythecnic CYLindrical code (TOPCYL) has been added in order to simulate antennas facing cylindrical plasma columns. This feature allows the analysis and design of RF heating systems for applications as VASIMR-like plasma thrusters and plasma-surface-interaction (PSI) experiments. In the present work, the theoretical basis and implementation of TOPCYL is presented, as well as the results obtained on simulating antennas for the ICRF and 2,45 GHz regimes.

  1. Topica: a Virtual Prototyping Suite for Plasma Facing Antennas

    NASA Astrophysics Data System (ADS)

    Lancellotti, Vito; Maggiora, Riccardo; Vecchi, Giuseppe; Kyrytsya, Volodymyr

    2002-11-01

    An innovative tool has been realized for the simulation of 3-dimensional Ion Cyclotron Radio Frequency (ICRF) antennas in a realistic geometry and with an accurate plasma model. The approach to the problem is based on an integral-equation formulation for the self-consistent evaluation of the current distribution on antennas facing a plasma in a slab geometry. The plasma enters the formalism via a surface impedance matrix; for this reason any plasma model can be used (presently the FELICE code has been adopted). A vacuum-term extraction and an analytical evaluation of some integrals are employed that permit to significantly reduce the integration support and to obtain a high numerical efficiency leading to the practical possibility of using sub-domain basis functions on each conductor of the antenna system. Calculation of field distributions (both magnetic and electric), useful for sheath considerations, is included. This tool has been implemented in a suite that is modular and applicable to ICRF antenna structures of arbitrary shape. This new simulation tool can assist during the detailed design phase and for this reason can be referred to as a "Virtual Prototyping Laboratory" (VPL). The VPL has been tested against assessed codes and against measurements of mock-up and prototype antennas.

  2. Correlation between excitation of Alfven modes and degradation of ICRF heating efficiency in TFTR

    SciTech Connect

    Bernabei, S.; Chang, Z.; Darrow, D.

    1997-05-01

    Alfven modes are excited by energetic ions in TFTR during intense minority ICRF heating. There is a clear threshold in rf power above which the modes are destabilized. The net effect of these modes is the increase of the fast ion losses, with an associated saturation of the ion tail energy and of the efficiency of the heating. Typically, several modes are excited with progressive n-numbers, with frequencies in the neighborhood of 200 kHz. Results suggest that Energetic Particle Modes (EPM), mostly unseen by the Mirnov coils, are generated near the center and are responsible for the ion losses. Stronger global TAE modes, which are destabilized by the stream of displaced fast ions, appear responsible only for minor losses.

  3. ICRF heating of deuterium-tritium plasmas in TFTR

    SciTech Connect

    Taylor, G.; Murakami, M.; Adler, H.

    1995-03-01

    The first experiments to heat D-T plasmas in the ion cyclotron range of frequencies (ICRF) have been performed on the Tokamak Fusion Test Reactor (TFTR). These experiments have two major objectives: to study the RF physics of ICRF-heated D-T plasmas and to enhance the performance of D-T discharges. Experiments have been conducted at 43 MHz with out-of-phase current strap excitation to explore n{sub T}/n{sub e} concentrations up to approximately 40%. In these experiments n{sub T}/n{sub e} was limited by D recycling from the carbon walls. The location of the T resonance was varied by changing the toroidal magnetic field, and the RF power was modulated (f{sub mod}=5-10 Hz) to elucidate competing heating mechanisms. Up to 5.8 MW of ICRF heating has been coupled into D-T plasmas. The addition of 5.5 MW of ICRF heating to a D-T supershot resulted in an increase in central ion temperature from 26 to 36 keV and an increase in central electron temperature from 8 to 10.5 keV. Up to 80% of the absorbed ICRF power was coupled directly to ions, in good agreement with computer code predictions. These results extrapolate to efficient T heating in future devices such as ITER.

  4. The Position/Structure Stability of Four ICRF2 Sources

    NASA Technical Reports Server (NTRS)

    Fomalont, Ed; Johnston, Kenneth; Fey, Alan; Boboltz, Dave; Oyama, Tomoaki; Honma, Mareki

    2010-01-01

    Four compact radio sources in the International Celestial Reference Frame (ICRF2) catalog were observed using phase referencing with the VLBA at 43, 23, and 8.6-GHz, and with VERA at 23-GHz over a one-year period. The goal was to determine the stability of the radio cores and to assess structure effects associated with positions in the ICRF2. Conclusions are: (1) 43-GHz VLBI high-resolution observations are often needed to determine the location of the radio core. (2) Over the observing period, the relative positions among the four radio cores were constant to 0.02 mas, suggesting that once the true radio core is identified, it remains stationary in the sky to this accuracy. (3) The emission in 0556+238, one of the four sources investigated and one of the 295 ICRF2 defining sources, was dominated by a strong component near the core and moved 0.1 mas during the year. (4) Comparison of the VLBA images at 43, 23, and 8.6-GHz with the ICRF2 positions suggests that the 8-GHz structure is often dominated by a bright non-core component. The measured ICRF2 position can be displaced more than 0.5 mas from the radio core and partake in the motion of the bright jet component.

  5. Deployable antenna

    NASA Technical Reports Server (NTRS)

    Fink, Patrick W. (Inventor); Dobbins, Justin A. (Inventor); Lin, Greg Y. (Inventor); Chu, Andrew W. (Inventor); Scully, Robert C. (Inventor)

    2006-01-01

    A deployable antenna and method for using wherein the deployable antenna comprises a collapsible membrane having at least one radiating element for transmitting electromagnetic waves, receiving electromagnetic waves, or both.

  6. JET ITER-Like Antenna Analysis Using the TOPICA Code

    NASA Astrophysics Data System (ADS)

    Milanesio, D.; Maggiora, R.

    2009-11-01

    In this work, we carried out the analysis of the recently installed JET ITER-Like antenna with TOPICA code. Comparisons between TOPICA simulations and measurements taken during the actual experiment are instead part of the overview talk on the JET ITER-Like antenna [4]. As routinely done for all simulated antennas, TOPICA inputs are the technical drawings of the launcher and the accurate density and temperature profiles, which, in this case, have been provided by the JET team. The standard outputs are the input parameters of the antenna, namely the impedance matrix, the electric current distribution and the electric field pattern at the interface between the antenna region and the plasma column. This work, together with [4], provides an additional proof that the code can be adopted to predict the behavior of the JET ITER-Like antenna, and to confidently pass to the next step, i.e. using TOPICA for the challenging task of optimizing the complex design of the actual ITER antenna. More generally viewed, the possibility to reliably simulate the detailed geometry of an ICRF antenna, given a realistic plasma description, and to obtain the actual antenna input parameters, is of paramount importance to evaluate and predict the system performances, and to assist in system operation.

  7. JET ITER-Like Antenna Analysis Using the TOPICA Code

    SciTech Connect

    Milanesio, D.; Maggiora, R.

    2009-11-26

    In this work, we carried out the analysis of the recently installed JET ITER-Like antenna with TOPICA code. Comparisons between TOPICA simulations and measurements taken during the actual experiment are instead part of the overview talk on the JET ITER-Like antenna [4]. As routinely done for all simulated antennas, TOPICA inputs are the technical drawings of the launcher and the accurate density and temperature profiles, which, in this case, have been provided by the JET team. The standard outputs are the input parameters of the antenna, namely the impedance matrix, the electric current distribution and the electric field pattern at the interface between the antenna region and the plasma column. This work, together with [4], provides an additional proof that the code can be adopted to predict the behavior of the JET ITER-Like antenna, and to confidently pass to the next step, i.e. using TOPICA for the challenging task of optimizing the complex design of the actual ITER antenna. More generally viewed, the possibility to reliably simulate the detailed geometry of an ICRF antenna, given a realistic plasma description, and to obtain the actual antenna input parameters, is of paramount importance to evaluate and predict the system performances, and to assist in system operation.

  8. Benchmarking ICRF Full-wave Solvers for ITER

    SciTech Connect

    R. V. Budny, L. Berry, R. Bilato, P. Bonoli, M. Brambilla, R. J. Dumont, A. Fukuyama, R. Harvey, E. F. Jaeger, K. Indireshkumar, E. Lerche, D. McCune, C. K. Phillips, V. Vdovin, J. Wright, and members of the ITPA-IOS

    2011-01-06

    Abstract Benchmarking of full-wave solvers for ICRF simulations is performed using plasma profiles and equilibria obtained from integrated self-consistent modeling predictions of four ITER plasmas. One is for a high performance baseline (5.3 T, 15 MA) DT H-mode. The others are for half-field, half-current plasmas of interest for the pre-activation phase with bulk plasma ion species being either hydrogen or He4. The predicted profiles are used by six full-wave solver groups to simulate the ICRF electromagnetic fields and heating, and by three of these groups to simulate the current-drive. Approximate agreement is achieved for the predicted heating power for the DT and He4 cases. Factor of two disagreements are found for the cases with second harmonic He3 heating in bulk H cases. Approximate agreement is achieved simulating the ICRF current drive.

  9. Theoretical analysis of the EAST 4-strap ion cyclotron range of frequency antenna with variational theory

    NASA Astrophysics Data System (ADS)

    Zhang, Jia-Hui; Zhang, Xin-Jun; Zhao, Yan-Ping; Qin, Cheng-Ming; Chen, Zhao; Yang, Lei; Wang, Jian-Hua

    2016-08-01

    A variational principle code which can calculate self-consistently currents on the conductors is used to assess the coupling characteristic of the EAST 4-strap ion cyclotron range of frequency (ICRF) antenna. Taking into account two layers of antenna conductors without lateral frame but with slab geometry, the antenna impedances as a function of frequency and the structure of RF field excited inside the plasma in various phasing cases are discussed in this paper. Project supported by the National Magnetic Confinement Fusion Science Program, China (Grant No. 2015GB101001) and the National Natural Science Foundation of China (Grant Nos. 11375236 and 11375235).

  10. User Antennas

    NASA Technical Reports Server (NTRS)

    Jamnejad, Vahraz; Cramer, Paul

    1990-01-01

    The following subject areas are covered: (1) impact of frequency change of user and spacecraft antenna gain and size; (2) basic personal terminal antennas (impact of 20/30 GHz frequency separation; parametric studies - gain, size, weight; gain and figure of merit (G/T); design data for selected antenna concepts; critical technologies and development goals; and recommendations); and (3) user antenna radiation safety concerns.

  11. Linking the Planetary Ephemerides to the ICRF

    NASA Astrophysics Data System (ADS)

    Folkner, William; Kuchynka, Petr

    2012-08-01

    An extensive campaign of very long baseline interferometry (VLBI) and range measurements of spacecraft in orbit about Mars have been performed by the NASA Deep Space Network since 1999 in order to support increasingly stringent targeting for spacecraft landings at Mars. The measurement campaign has intensified in the last few years leading up to the Mars Science Laboratory (MSL) landing on Mars in August 2012. MSL requires that the orbit of Mars with respect to Earth be determined with an accuracy better than 300 meters. As a result of the measurement campaign, the orientation of the orbits of the Earth and Mars with respect to the International Celestial Reference Frame (ICRF) has been determined with an accuracy of 0.1 milli - arcseconds. The distances from the Earth to the Sun are estimated to have uncertainties of a few meters for several centuries about the current epoch. The improved ephemeris of the Earth provides an accurate reference for pulsar timing experiments. The accuracies of the orbits of Mercury, Venus, and Saturn have been recently improved from measurements of the MESSENGER, Venus Express, and Cassini spacecraft respectively. The current planetary observation sets and residuals to fitted ephemerides will be described. The next major improvement in the planetary ephemerides is expected to come with the arrival of the Juno mission at Jupiter in 2016.

  12. Bulk ion heating with ICRF waves in tokamaks

    SciTech Connect

    Mantsinen, M. J.; Bilato, R.; Bobkov, V. V.; Kappatou, A.; McDermott, R. M.; Odstrčil, T.; Tardini, G.; Bernert, M.; Dux, R.; Maraschek, M.; Noterdaeme, J.-M.; Ryter, F.; Stober, J.; Nocente, M.; Hellsten, T.; Mantica, P.; Tardocchi, M.; Nielsen, S. K.; Rasmussen, J.; Stejner, M.; and others

    2015-12-10

    Heating with ICRF waves is a well-established method on present-day tokamaks and one of the heating systems foreseen for ITER. However, further work is still needed to test and optimize its performance in fusion devices with metallic high-Z plasma facing components (PFCs) in preparation of ITER and DEMO operation. This is of particular importance for the bulk ion heating capabilities of ICRF waves. Efficient bulk ion heating with the standard ITER ICRF scheme, i.e. the second harmonic heating of tritium with or without {sup 3}He minority, was demonstrated in experiments carried out in deuterium-tritium plasmas on JET and TFTR and is confirmed by ICRF modelling. This paper focuses on recent experiments with {sup 3}He minority heating for bulk ion heating on the ASDEX Upgrade (AUG) tokamak with ITER-relevant all-tungsten PFCs. An increase of 80% in the central ion temperature T{sub i} from 3 to 5.5 keV was achieved when 3 MW of ICRF power tuned to the central {sup 3}He ion cyclotron resonance was added to 4.5 MW of deuterium NBI. The radial gradient of the T{sub i} profile reached locally values up to about 50 keV/m and the normalized logarithmic ion temperature gradients R/LT{sub i} of about 20, which are unusually large for AUG plasmas. The large changes in the T{sub i} profiles were accompanied by significant changes in measured plasma toroidal rotation, plasma impurity profiles and MHD activity, which indicate concomitant changes in plasma properties with the application of ICRF waves. When the {sup 3}He concentration was increased above the optimum range for bulk ion heating, a weaker peaking of the ion temperature profile was observed, in line with theoretical expectations.

  13. Bulk ion heating with ICRF waves in tokamaks

    NASA Astrophysics Data System (ADS)

    Mantsinen, M. J.; Bilato, R.; Bobkov, V. V.; Kappatou, A.; McDermott, R. M.; Nocente, M.; Odstrčil, T.; Tardini, G.; Bernert, M.; Dux, R.; Hellsten, T.; Mantica, P.; Maraschek, M.; Nielsen, S. K.; Noterdaeme, J.-M.; Rasmussen, J.; Ryter, F.; Stejner, M.; Stober, J.; Tardocchi, M.

    2015-12-01

    Heating with ICRF waves is a well-established method on present-day tokamaks and one of the heating systems foreseen for ITER. However, further work is still needed to test and optimize its performance in fusion devices with metallic high-Z plasma facing components (PFCs) in preparation of ITER and DEMO operation. This is of particular importance for the bulk ion heating capabilities of ICRF waves. Efficient bulk ion heating with the standard ITER ICRF scheme, i.e. the second harmonic heating of tritium with or without 3He minority, was demonstrated in experiments carried out in deuterium-tritium plasmas on JET and TFTR and is confirmed by ICRF modelling. This paper focuses on recent experiments with 3He minority heating for bulk ion heating on the ASDEX Upgrade (AUG) tokamak with ITER-relevant all-tungsten PFCs. An increase of 80% in the central ion temperature Ti from 3 to 5.5 keV was achieved when 3 MW of ICRF power tuned to the central 3He ion cyclotron resonance was added to 4.5 MW of deuterium NBI. The radial gradient of the Ti profile reached locally values up to about 50 keV/m and the normalized logarithmic ion temperature gradients R/LTi of about 20, which are unusually large for AUG plasmas. The large changes in the Ti profiles were accompanied by significant changes in measured plasma toroidal rotation, plasma impurity profiles and MHD activity, which indicate concomitant changes in plasma properties with the application of ICRF waves. When the 3He concentration was increased above the optimum range for bulk ion heating, a weaker peaking of the ion temperature profile was observed, in line with theoretical expectations.

  14. VUV Study of Impurity Generation during Icrf Heating Experiments on the Alcator C Tokamak

    NASA Astrophysics Data System (ADS)

    Manning, Herbert Leslie, Jr.

    A 2.2 meter grazing incidence VUV monochromator has been converted into a time-resolving spectrograph by the addition of a new detector system, based on a microchannel plate image intensifier linked to a 1024-element linear photodiode array. The system covers the wavelength range 15-1200 (ANGSTROM) (typically 40 (ANGSTROM) at a time) with resolution of up to .3 (ANGSTROM) FWHM. Time resolution is selectable down to 0.5 msec. The system sensitivity was absolutely calibrated below 150 (ANGSTROM) by a soft X-ray calibration facility. The spectrograph was installed on the Alcator C tokamak at MIT to monitor plasma impurity emission. There, cross-calibration with a calibrated EUV monochromator was performed above 400 (ANGSTROM). Calibration results, system performance characteristics, and data from Alcator C are presented. Observations of impurity behavior are presented from a series of ICRF heating experiments (180 MHz, 50 -400 kW) performed on the Alcator C tokamak, using graphite limiters and stainless steel antenna Faraday shields. Large increases in metal impurity levels were seen during the RF pulse, with iron increasing by a factor of 12 at the highest RF powers. Much smaller increases in carbon and oxygen were seen. Potential impurity sources and release mechanisms are discussed. Analysis of inferred iron source rates shows a linear dependence on RF power up to 400 kW, with no clear dependence on resonance conditions or bulk plasma parameters. However, a sharp increase in electron temperature, T(,e), in the limiter shadow region, seen during the ICRF pulse, was well correlated with the iron influx rate. It is concluded from this and other evidence that enhanced sputtering of the Faraday shield due to an elevated sheath potential ((phi)(,sh) (TURN) 3T(,e)) is the primary source of metal impurities during ICRF heating on Alcator C. This process, occurring at the limiter, is the dominant source of carbon and oxygen. These results are consistent with sputtering

  15. Development of Scientific Simulation 3D Full Wave ICRF Code for Stellarators and Heating/CD Scenarios Development

    SciTech Connect

    Vdovin V.L.

    2005-08-15

    In this report we describe theory and 3D full wave code description for the wave excitation, propagation and absorption in 3-dimensional (3D) stellarator equilibrium high beta plasma in ion cyclotron frequency range (ICRF). This theory forms a basis for a 3D code creation, urgently needed for the ICRF heating scenarios development for the operated LHD, constructed W7-X, NCSX and projected CSX3 stellarators, as well for re evaluation of ICRF scenarios in operated tokamaks and in the ITER . The theory solves the 3D Maxwell-Vlasov antenna-plasma-conducting shell boundary value problem in the non-orthogonal flux coordinates ({Psi}, {theta}, {var_phi}), {Psi} being magnetic flux function, {theta} and {var_phi} being the poloidal and toroidal angles, respectively. All basic physics, like wave refraction, reflection and diffraction are self consistently included, along with the fundamental ion and ion minority cyclotron resonances, two ion hybrid resonance, electron Landau and TTMP absorption. Antenna reactive impedance and loading resistance are also calculated and urgently needed for an antenna -generator matching. This is accomplished in a real confining magnetic field being varying in a plasma major radius direction, in toroidal and poloidal directions, through making use of the hot dense plasma wave induced currents with account to the finite Larmor radius effects. We expand the solution in Fourier series over the toroidal ({var_phi}) and poloidal ({theta}) angles and solve resulting ordinary differential equations in a radial like {Psi}-coordinate by finite difference method. The constructed discretization scheme is divergent-free one, thus retaining the basic properties of original equations. The Fourier expansion over the angle coordinates has given to us the possibility to correctly construct the ''parallel'' wave number k{sub //}, and thereby to correctly describe the ICRF waves absorption by a hot plasma. The toroidal harmonics are tightly coupled with each

  16. Reconfigurable antenna pattern verification

    NASA Technical Reports Server (NTRS)

    Drexler, Jerome P. (Inventor); Becker, Robert C. (Inventor); Meyers, David W. (Inventor); Muldoon, Kelly P. (Inventor)

    2013-01-01

    A method of verifying programmable antenna configurations is disclosed. The method comprises selecting a desired antenna configuration from a plurality of antenna configuration patterns, with the selected antenna configuration forming at least one reconfigurable antenna from reconfigurable antenna array elements. The method validates the formation of the selected antenna configuration to determine antenna performance of the at least one reconfigurable antenna.

  17. RF Power to Plasma Increase Using EBG Surfaces in IC and LH Antennas

    NASA Astrophysics Data System (ADS)

    Guadamuz, Saul; Maggiora, Riccardo

    2009-11-01

    High impedance surfaces or electromagnetic band gap (EBG) surfaces have proved themselves to be useful in wireless communications applications due to their unique characteristics such as no propagating surface wave support, no conduction of RF current for a given bandwidth, in-phase electromagnetic reflection and non-inverted image of the electric charge in front of them [1]. These characteristics make possible to design compact antennas achieving better performance in terms of radiation and input impedance. ICRF and LH antennas in plasma experiments can take advantage of using EBG surfaces. One of the main issues in ICRF plasma heating is the high mismatch between the feeding lines and the antenna inputs. The adoption of EBG surfaces in the ICRF antenna structure and the advantages offered by a predictive designing tool as TOPICA [2] offer the possibility to improve significantly the coupled power to plasma. The adoption of EBG surfaces in the LH waveguides permits to reduce the major dimension of waveguides not affecting the propagation. It is then possible to manufacture compact LH arrays of waveguides. [4pt] [1] IEEE Trans. Microwave Theory Tech., vol. 47, pp. 2059--2074, Nov. 1999. [0pt] [2] Nucl. Fusion, 46 (2006) S476.

  18. JET ITER-Like Antenna Simulation Using the TOPICA Code

    NASA Astrophysics Data System (ADS)

    Milanesio, Daniele; Maggiora, Riccardo

    2009-11-01

    In this work, we carried out the analysis of the recently installed JET ITER-Like antenna with TOPICA code. Comparisons between TOPICA simulations and measurements taken during the actual experiment are presented. As routinely done for all simulated antennas, TOPICA inputs are the technical drawings of the launcher and the accurate density and temperature profiles, which, in this case, have been provided by the JET team. The standard outputs are the input parameters of the antenna, namely the impedance matrix, the electric current distribution and the electric field pattern at the interface between the antenna region and the plasma column. This work provides an additional proof that the code can be adopted to predict the behavior of the ITER antenna, and to confidently use TOPICA for the challenging task of optimizing the complex design of the actual ITER antenna. More generally viewed, the possibility to reliably simulate the detailed geometry of an ICRF antenna, given a realistic plasma description, and to obtain the actual antenna input parameters, is of paramount importance to evaluate and predict the system performances, and to assist in system operation.

  19. Modeling of high power ICRF heating experiments on TFTR

    SciTech Connect

    Phillips, C.K.; Wilson, J.R.; Bell, M.; Fredrickson, E.; Hosea, J.C.; Majeski, R.; Ramsey, A.; Rogers, J.H.; Schilling, G.; Skinner, C.; Stevens, J.E.; Taylor, G.; Wong, K.L.; Khudaleev, A.; Petrov, M.P.; Murakami, M.

    1993-04-01

    Over the past two years, ICRF heating experiments have been performed on TFTR in the hydrogen minority heating regime with power levels reaching 11.2 MW in helium-4 majority plasmas and 8.4 MW in deuterium majority plasmas. For these power levels, the minority hydrogen ions, which comprise typically less than 10% of the total electron density, evolve into la very energetic, anisotropic non-Maxwellian distribution. Indeed, the excess perpendicular stored energy in these plasmas associated with the energetic minority tail ions is often as high as 25% of the total stored energy, as inferred from magnetic measurements. Enhanced losses of 0.5 MeV protons consistent with the presence of an energetic hydrogen component have also been observed. In ICRF heating experiments on JET at comparable and higher power levels and with similar parameters, it has been suggested that finite banana width effects have a noticeable effect on the ICRF power deposition. In particular, models indicate that finite orbit width effects lead to a reduction in the total stored energy and of the tail energy in the center of the plasma, relative to that predicted by the zero banana width models. In this paper, detailed comparisons between the calculated ICRF power deposition profiles and experimentally measured quantities will be presented which indicate that significant deviations from the zero banana width models occur even for modest power levels (P{sub rf} {approximately} 6 MW) in the TFTR experiments.

  20. Modeling of high power ICRF heating experiments on TFTR

    SciTech Connect

    Phillips, C.K.; Wilson, J.R.; Bell, M.; Fredrickson, E.; Hosea, J.C.; Majeski, R.; Ramsey, A.; Rogers, J.H.; Schilling, G.; Skinner, C.; Stevens, J.E.; Taylor, G.; Wong, K.L. . Plasma Physics Lab.); Khudaleev, A.; Petrov, M.P. ); Murakami, M. )

    1993-01-01

    Over the past two years, ICRF heating experiments have been performed on TFTR in the hydrogen minority heating regime with power levels reaching 11.2 MW in helium-4 majority plasmas and 8.4 MW in deuterium majority plasmas. For these power levels, the minority hydrogen ions, which comprise typically less than 10% of the total electron density, evolve into la very energetic, anisotropic non-Maxwellian distribution. Indeed, the excess perpendicular stored energy in these plasmas associated with the energetic minority tail ions is often as high as 25% of the total stored energy, as inferred from magnetic measurements. Enhanced losses of 0.5 MeV protons consistent with the presence of an energetic hydrogen component have also been observed. In ICRF heating experiments on JET at comparable and higher power levels and with similar parameters, it has been suggested that finite banana width effects have a noticeable effect on the ICRF power deposition. In particular, models indicate that finite orbit width effects lead to a reduction in the total stored energy and of the tail energy in the center of the plasma, relative to that predicted by the zero banana width models. In this paper, detailed comparisons between the calculated ICRF power deposition profiles and experimentally measured quantities will be presented which indicate that significant deviations from the zero banana width models occur even for modest power levels (P[sub rf] [approximately] 6 MW) in the TFTR experiments.

  1. Control and Data Acquisition System for KSTAR ICRF

    SciTech Connect

    Wang, S. J.; Kwak, J. G.

    2009-11-26

    An ICRF discharge cleaning and a plasma heating experiment were performed in KSTAR toka-mak. For an automated operation and the diagnostics of the ICRF system, the ICRF local network was designed and implemented. This internal network provides monitoring, RF protection, remote control and RF diagnostics. All the functions of the control system were realized by customized DSP units. The DSP units were tied by a local network in parallel. For RF diagnostics, a detector based on digital I/Q demodulation technique was fabricated. The I/Q detector collects the RF amplitude and phase at the same time without errors from I/Q imbalance inherent in an analog counterpart. During the first experimental campaign of the KSTAR tokamak, the control system was operated as expected without any major problems such as affecting the tokamak operation. The transmitter was protected from the harmful over-voltage events through a reliable operation of the system. Details of ICRF control system and RF detecting technique with a brief experimental result will be presented.

  2. Measurements of ICRF (ion cyclotron range of frequencies) loading with a ridged waveguide coupler on PLT

    SciTech Connect

    Greene, G.J.; Wilson, J.R.; Colestock, P.L.; Fortgang, C.M.; Hosea, J.C.; Hwang, D.Q.; Nagy, A.

    1987-11-01

    An ICRF ridged waveguide coupler has been installed on PLT for measurements of plasma loading. The coupler was partially filled with TiO/sub 2/ dielectric in order to sufficiently lower the cutoff frequency and utilized a tapered ridge for improved matching. Vacuum field measurements indicated a single propagating mode in the coupler and emphasized the importance of considering the fringing fields at the mouth of the waveguide. Low power experiments were carried out at 72.6 and 95.0 MHz without any external impedance matching network. Plasma loading increased rapidly as the face of the coupler approached the plasma, and, at fixed position, increased with line-averaged plasma density. At the lower frequency, the reflection coefficient exhibited a minimum (<8%) at a particular coupler position. At both frequencies, measurements indicated efficient power coupling to the plasma. Magnetic probe signals showed evidence of dense eigenmodes suggesting excitation of the fast wave. 24 refs., 13 figs.

  3. Use of .sup.3 He.sup.30 + ICRF minority heating to simulate alpha particle heating

    DOEpatents

    Post, Jr., Douglass E.; Hwang, David Q.; Hovey, Jane

    1986-04-22

    Neutron activation due to high levels of neutron production in a first heated deuterium-tritium plasma is substantially reduced by using Ion Cyclotron Resonance Frequency (ICRF) heating of energetic .sup.3 He.sup.++ ions in a second deuterium-.sup.3 He.sup.++ plasma which exhibit an energy distribution and density similar to that of alpha particles in fusion reactor experiments to simulate fusion alpha particle heating in the first plasma. The majority of the fast .sup.3 He.sup.++ ions and their slowing down spectrum can be studied using either a modulated hydrogen beam source for producing excited states of He.sup.+ in combination with spectrometers or double charge exchange with a high energy neutral lithium beam and charged particle detectors at the plasma edge. The maintenance problems thus associated with neutron activation are substantially reduced permitting energetic alpha particle behavior to be studied in near term large fusion experiments.

  4. ICRF Heating with {omega}<{omega}{sub ci} in Alcator C-Mod

    SciTech Connect

    Phillips, C. K.; Hosea, J. C.; Valeo, E. J.; Wilson, J. R.; Bonoli, P. T.; Lin, Y.; Porkolab, M.; Wright, J. C.; Wukitch, S. J.

    2007-09-28

    The TORIC 2D full wave simulation code has been used to study the dynamics of waves with {omega}<{omega}{sub ci} everywhere for all ions in the Alcator C-Mod tokamak. This potential heating regime can be accessed uniquely on C-Mod, because of its high magnetic field capability, B{sub T}{<=}8 T, and variable ICRF source frequency, 40-80 MHz. The simulations indicate that the launched fast waves can mode convert to a short wavelength slow wave on the high field side of the discharge that damps primarily on electrons. The degree to which the mode converted wave penetrates into the core of the plasma is found to depend on the equilibrium density profile.

  5. IVS Observation of ICRF2-Gaia Transfer Sources

    NASA Astrophysics Data System (ADS)

    Le Bail, K.; Gipson, J. M.; Gordon, D.; MacMillan, D. S.; Behrend, D.; Thomas, C. C.; Bolotin, S.; Himwich, W. E.; Baver, K. D.; Corey, B. E.; Titus, M.; Bourda, G.; Charlot, P.; Collioud, A.

    2016-03-01

    The second realization of the International Celestial Reference Frame (ICRF2), which is the current fundamental celestial reference frame adopted by the International Astronomical Union, is based on Very Long Baseline Interferometry (VLBI) data at radio frequencies in X band and S band. The European Space Agency’s Gaia mission, launched on 2013 December 19, started routine scientific operations in 2014 July. By scanning the whole sky, it is expected to observe ∼500,000 Quasi Stellar Objects in the optical domain an average of 70 times each during the five years of the mission. This means that, in the future, two extragalactic celestial reference frames, at two different frequency domains, will coexist. It will thus be important to align them very accurately. In 2012, the Laboratoire d’Astrophysique de Bordeaux (LAB) selected 195 sources from ICRF2 that will be observed by Gaia and should be suitable for aligning the radio and optical frames: they are called ICRF2-Gaia transfer sources. The LAB submitted a proposal to the International VLBI Service (IVS) to regularly observe these ICRF2-Gaia transfer sources at the same rate as Gaia observes them in the optical realm, e.g., roughly once a month. We describe our successful effort to implement such a program and report on the results. Most observations of the ICRF2-Gaia transfer sources now occur automatically as part of the IVS source monitoring program, while a subset of 37 sources requires special attention. Beginning in 2013, we scheduled 25 VLBI sessions devoted in whole or in part to measuring these 37 sources. Of the 195 sources, all but one have been successfully observed in the 12 months prior to 2015 September 01. Of the sources, 87 met their observing target of 12 successful sessions per year. The position uncertainties of all of the ICRF2-Gaia transfer sources have improved since the start of this observing program. For a subset of 24 sources whose positions were very poorly known, the uncertainty

  6. Revisiting the VLBA Calibrator Surveys for ICRF3

    NASA Astrophysics Data System (ADS)

    Gordon, David; Ma, Chopo; Jacobs, Christopher; Fey, Alan; Gaume, Ralph; Beasley, Anthony; Peck, Alison; Boboltz, David; Titov, Oleg; Charlot, Patrick

    2015-08-01

    The original VLBA Calibrator (VCS) surveys were a set of 24 24-hr VLBA sessions between 1994 and 2007 in which ~2600 compact radio sources were observed in X/S bands to obtain precise positions and snapsot images. Most were observed in only one session but they vastly expanded the pool of calibrator sources available for phase-referencing VLBI. These sources were later incorporated into ICRF2, but within ICRF2 they became a second class compared to the other ICRF2 sources observed in regular Mark3/Mark4/RDV VLBI geodesy and astrometry sessions over nearly 30 years. The VCS sources represented 2/3 of ICRF2, but they had formal errors approximately 5 times greater, on average, than the other 1/3. In order to reduce this 2 class distinction, the VCS-II team was formed to re-observe these sources for ICRF3 and improve their usefulness as phase-referencing calibrators. We report here on the re-observations of 2400 of these sources in 8 VLBA sessions in 2014 and 2015. The new observations were made at 2 GBits/sec versus the 128 MBits/sec of the original VCS sessions, and thus are considerably more sensitive. Some 2000 'old' VCS sources have been re-observed and their formal position errors have improved by an average factor of 3.6 in RA and Dec. And ~300 'new' sources (not detected in the original VCS analysis) have also now been detected. Mapping of these sources is also being performed and we anticipate being able to compute structure indices for them as well.

  7. Simulations of gas puff effects on edge density and ICRF coupling in ASDEX upgrade using EMC3-Eirene

    SciTech Connect

    Zhang, W.; Lunt, T.; Bobkov, V.; Coster, D.; Brida, D.; Noterdaeme, J.-M.; Jacquet, P.; Feng, Y.

    2015-12-10

    Simulations were carried out with the 3D plasma transport code EMC3-EIRENE, to study the deuterium gas (D{sub 2}) puff effects on edge density and the coupling of Ion Cyclotron Range of Frequency (ICRF) power in ASDEX Upgrade. Firstly we simulated an inter-ELM phase of an H-mode discharge with a moderate (1.2 × 10{sup 22} electrons/s) lower divertor gas puff. Then we changed the gas source positions to the mid-plane or top of machine while keeping other conditions the same. Cases with different mid-plane or top gas valves are investigated. Our simulations indicate that compared to lower divertor gas puffing, the mid-plane gas puff can enhance the local density in front of the antennas most effectively, while a rather global (toroidally uniform) but significantly smaller enhancement is found for top gas puffing. Our results show quantitative agreement with the experiments.

  8. Electrochemically Programmable Plasmonic Antennas.

    PubMed

    Dong, Shi; Zhang, Kai; Yu, Zhiping; Fan, Jonathan A

    2016-07-26

    Plasmonic antennas are building blocks in advanced nano-optical systems due to their ability to tailor optical response based on their geometry. We propose an electrochemical approach to program the optical properties of dipole antennas in a scalable, fast, and energy-efficient manner. These antennas comprise two arms, one serving as an anode and the other a cathode, separated by a solid electrolyte. As a voltage is applied between the antenna arms, a conductive filament either grows or dissolves within the electrolyte, modifying the antenna load. We probe the dynamics of stochastic filament formation and their effects on plasmonic mode programming using a combination of three-dimensional optical and electronic simulations. In particular, we identify device operation regimes in which the charge-transfer plasmon mode can be programmed to be "on" or "off." We also identify, unexpectedly, a strong correlation between DC filament resistance and charge-transfer plasmon mode frequency that is insensitive to the detailed filament morphology. We envision that the scalability of our electrochemical platform can generalize to large-area reconfigurable metamaterials and metasurfaces for on-chip and free-space applications. PMID:27328022

  9. Plasma-Surface Interactions and RF Antennas

    NASA Astrophysics Data System (ADS)

    Jenkins, Thomas; Smithe, D. N.; Beckwith, K.; Davidson, B. D.; Kruger, S. E.; Pankin, A. Y.; Roark, C. M.

    2015-11-01

    Implementation of recently developed finite-difference time-domain (FDTD) modeling techniques on high-performance computing platforms allows RF power flow, and antenna near- and far-field behavior, to be studied in realistic experimental ion-cyclotron resonance heating scenarios at previously inaccessible levels of resolution. We present results and 3D animations of high-performance (10k-100k core) FDTD simulations of Alcator C-Mod's field-aligned ICRF antenna on the Titan supercomputer, considering (a) the physics of slow wave excitation in the immediate vicinity of the antenna hardware and in the scrape-off layer for various edge densities, and (b) sputtering and impurity production, as driven by self-consistent sheath potentials at antenna surfaces. Related research efforts in low-temperature plasma modeling, including the use of proper orthogonal decomposition methods for PIC/fluid modeling and the development of plasma chemistry tools (e.g. a robust and flexible reaction database, principal path reduction analysis capabilities, and improved visualization options), will also be summarized. Supported by U.S. DoE SBIR Phase I/II Award DE-SC0009501 and ALCC/OLCF.

  10. Active antenna

    NASA Astrophysics Data System (ADS)

    Sutton, John F.

    1994-05-01

    An antenna, which may be a search coil, is connected to an operational amplifier circuit which provides negative impedances, each of which is in the order of magnitude of the positive impedances which characterize the antenna. The antenna is connected to the inverting input of the operational amplifier; a resistor is connected between the inverting input and the output of the operational amplifier; a capacitor-resistor network, in parallel, is connected between the output and the noninverting input of the operational amplifier; and a resistor is connected from the noninverting input and the circuit common. While this circuit provides a negative resistance and a negative inductance, in series, which appear, looking into the noninverting input of the operational amplifier, in parallel with the antenna, these negative impedances appear in a series loop with the antenna positive impedances, so as to algebraically add. This circuit is tuned by varying the various circuit components so that the negative impedances are very close, but somewhat less, in magnitude, to the antenna impedances. The result is to increase the sensitivity of the antenna by lowering its effective impedance. This, in turn, increases the effective area of the antenna, which may be broadband.

  11. Active antenna

    NASA Technical Reports Server (NTRS)

    Sutton, John F. (Inventor)

    1994-01-01

    An antenna, which may be a search coil, is connected to an operational amplifier circuit which provides negative impedances, each of which is in the order of magnitude of the positive impedances which characterize the antenna. The antenna is connected to the inverting input of the operational amplifier; a resistor is connected between the inverting input and the output of the operational amplifier; a capacitor-resistor network, in parallel, is connected between the output and the noninverting input of the operational amplifier; and a resistor is connected from the noninverting input and the circuit common. While this circuit provides a negative resistance and a negative inductance, in series, which appear, looking into the noninverting input of the operational amplifier, in parallel with the antenna, these negative impedances appear in a series loop with the antenna positive impedances, so as to algebraically add. This circuit is tuned by varying the various circuit components so that the negative impedances are very close, but somewhat less, in magnitude, to the antenna impedances. The result is to increase the sensitivity of the antenna by lowering its effective impedance. This, in turn, increases the effective area of the antenna, which may be broadband.

  12. Designing the IShTAR antenna: Physics and engineering aspects

    NASA Astrophysics Data System (ADS)

    Louche, F.; Jacquot, J.; Crombé, K.; Van Eester, D.; D'Inca, R.; Devaux, S.; Faudot, E.; Faugel, H.; Fünfgelder, H.; Heuraux, S.; Morgal, I.; Moritz, J.; Ochoukov, R.; Noterdaeme, J.-M.

    2015-12-01

    IShTAR (Ion cyclotron Sheath Test ARrangement) is a magnetised plasma test facility installed at the Max-Planck-Institut für Plasmaphysik in Garching, Germany. The main purpose of this device is the study of RF sheaths generated in front of ICRF (Ion Cyclotron Range of Frequency) antennas in magnetically confined plasmas. The plasma is generated by a helical RF antenna potentially able to reach a helicon mode. We present in this work recent modelling activities dedicated to IShTAR. On the one hand a parameterized magnetostatic model of the magnetic configuration was created with the finite element solver COMSOL Multiphysics [3]. The model considers two non-axial sets of coils and notably reproduces the magnetic field lines deviation at the center of the main vessel and the ripples observed during experiments. From this model we can infer that kA are required in the 2 main large coils of IShTAR for 1 kA in the 4 small coils to generate a "smooth" magnetic field along field lines. On the other hand an ICRF antenna has been designed for IShTAR. A tridimensional model of the IShTAR vessel was developed with the electromagnetic code MicroWave Studio (MWS [4]) for this purpose and a first antenna model made of a single strap inside a box was included. The strap is fed through the upper port located at the helicon source side. The antenna is fully immersed into the loading medium (plasma or homogeneous dielectric) and the curved strap front face is aligned with the magnetic surfaces to simplify the modelling. The initial design of this antenna has been studied with MWS in the presence of homogeneous dielectric. The presence of a back wall will be discussed.

  13. A high power experimental traveling wave antenna for fast wave heating and current drive in DIII-D and relevance to ITER

    SciTech Connect

    Phelps, D.A.; Ikezi, H.; Moeller, C.P.

    1995-10-01

    The impact of a contemplated conversion of the directly driven high power antenna arrays in DIII-D to externally tuned and coupled traveling wave antennas (TWAs) is evaluated based on empirical modeling, computer simulation and low power experiments. A regime of operation is predicted within the TWA passband in which the reflected power from the TWA approaches 0.1% during ELM-free H-mode. Furthermore, this reflected power does not exceed 1% and the optimum phase velocity produced by the TWA decreases less than 5% during ELMs. This resilient operating regime is phase shifted using external tuning stubs, thus providing considerable experimental flexibility. Over 90% plasma coupling efficiency is achieved by recovering the TWA output power using a novel traveling wave recirculator. Combining the above attributes with efficient plasma coupling even at large antenna-plasma distances and the lack of need for dynamic tuning, TWAs appear to offer great promise for ITER.

  14. ICRF Mode Conversion Studies with Phase Contrast Imaging and Comparisons with Full-Wave Simulations

    SciTech Connect

    Tsujii, N.; Bonoli, P. T.; Lin, Y.; Wright, J. C.; Wukitch, S. J.; Porkolab, M.; Jaeger, E. F.; Harvey, R. W.

    2011-12-23

    Waves in the ion cyclotron range of frequencies (ICRF) are widely used to heat toka-mak plasmas. In a multi-ion-species plasma, the FW converts to ion cyclotron waves (ICW) and ion Bernstein waves (IBW) around the ion-ion hybrid resonance (mode conversion). The mode converted wave is of interest as an actuator to optimise plasma performance through flow drive and current drive. Numerical simulations are essential to describe these processes accurately, and it is important that these simulation codes be validated. On Alcator C-Mod, direct measurements of the mode converted waves have been performed using Phase Contrast Imaging (PCI), which measures the line-integrated electron density fluctuations. The results were compared to full-wave simulations AORSA and TORIC. AORSA is coupled to a Fokker-Planck code CQL3D for self-consistent simulation of the wave electric field and the minority distribution function. The simulation results are compared to PCI measurements using synthetic diagnostic. The experiments were performed in D-H and D-{sup 3}He plasmas over a wide range of ion species concentrations. The simulations agreed well with the measurements in the strong absorption regime. However, the measured fluctuation intensity was smaller by 1-2 orders of magnitudes in the weakly abosorbing regime, and a realistic description of the plasma edge including dissipation and antenna geometry may be required in these cases.

  15. 3D simulations of gas puff effects on edge density and ICRF coupling in ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Bobkov, V.; Lunt, T.; Noterdaeme, J.-M.; Coster, D.; Bilato, R.; Jacquet, P.; Brida, D.; Feng, Y.; Wolfrum, E.; Guimarais, L.; the ASDEX Upgrade Team

    2016-03-01

    In recent experiments, a local gas puff was found to be an effective way to tailor the scrape-off layer (SOL) density and improve the ion cyclotron range of frequency (ICRF) power coupling in tokamaks. In order to quantitatively reproduce these experiments, to understand the corresponding physics and to optimize the gas valve positions and rates, simulations were carried out with the 3D edge plasma transport code EMC3-EIRENE in ASDEX Upgrade. An inter-ELM phase of an H-mode discharge with a moderate gas puff rate (1.2  ×  1022 electrons s-1) is used in our simulations. We simulated cases with gas puff in the lower divertor, the outer mid-plane and the top of the machine while keeping other conditions the same. Compared with the lower divertor gas puff, the outer mid-plane gas puff can increase the local density in front of the antennas most effectively, while a toroidally uniform but significantly smaller enhancement is found for the top gas puff. Good agreement between our simulations and experiments is obtained. With further simulations, the mechanisms of SOL density tailoring via local gas puffing and the strategies of gas puff optimization are discussed in the paper.

  16. Recent results from the TFTR ICRF DT Program

    SciTech Connect

    Rogers, J.H.; Darrow, D.; Majeski, R.

    1995-03-01

    The first experiments to be performed with ICRF heating of DT plasmas are reported. ICRF heating of minority ions, tritium (second harmonic resonance), as well as direct electron heating are being performed during the DT phase of TFTR. RF power modulation and Fourier transform techniques are used to attempt to elucidate the competition between tritium second harmonic, direct electron, and {sup 3}He fundamental heating in DT plasmas. A significant fraction of the RF power has been found to couple to the tritium ions via second harmonic heating. Relevant RF coupling physics is investigated using {sup 3}He minority heating (43 MHz), H minority heating (64 MHz), and mode conversion (43 MHz, comparable densities of {sup 3}He and {sup 4}He) at a toroidal field of 4.5T.

  17. Ion radial transport induced by ICRF waves in tokamaks

    SciTech Connect

    Chen, L.; Vaclavik, J.; Hammett, G.W.

    1987-05-01

    The wave-induced fluxes of energetic-trapped ions during ICRF heating of tokamak plasmas are calculated using quasilinear equations. A simple single particle model of this transport mechanism is also given. Both a convective flux proportional to k/sub phi/vertical bar E/sub +/vertical bar/sup 2/ and a diffusive flux proportional to k/sub phi//sup 2/vertical bar E/sub +/vertical bar/sup 2/ are found. Here, k/sub phi/ is the toroidal wave number and E/sub +/ is the left-hand polarized wave field. The convective flux may become significant for large k/sub phi/ if the wave spectrum is asymmetric in k/sub phi/. But for the conditions of most previous experiments, these calculations indicate that radial transport driven directly by the ICRF wave is unimportant.

  18. Observation of Central Toroidal Rotation Induced by ICRF on EAST

    NASA Astrophysics Data System (ADS)

    Pan, Xiayun; Wang, Fudi; Zhang, Xinjun; Lyu, Bo; Chen, Jun; Li, Yingying; Fu, Jia; Shi, Yuejiang; Yu, Yi; Ye, Minyou; Wan, Baonian

    2016-02-01

    Core plasma rotation of both L-mode and H-mode discharges with ion cyclotron range of frequency (ICRF) minority heating (MH) scheme was measured with a tangential X-ray imaging crystal spectrometer on EAST (Experimental Advanced Superconducting Tokamak). Co-current central impurity toroidal rotation change was observed in ICRF-heated L- and H-mode plasmas. Rotation increment as high as 30 km/s was generated at ∼1.7 MW ICRF power. Scaling results showed similar trend as the Rice scaling but with significant scattering, especially in L-mode plasmas. We varied the plasma current, toroidal field and magnetic configuration individually to study their effect on L-mode plasma rotation, while keeping the other major plasma parameters and heating unchanged during the scanning. It was found that larger plasma current could induce plasma rotation more efficiently. A scan of the toroidal magnetic field indicated that the largest rotation was obtained for on-axis ICRF heating. A comparison between lower-single-null (LSN) and double-null (DN) configurations showed that LSN discharges rendered a larger rotation change for the same power input and plasma parameters. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2013GB112004 and 2015GB103002), National Natural Science Foundation of China (Nos. 11175208, 11305212, 11375235, 11405212 and 11261140328), the Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology (2014FXCX003) and Brain Korea 21 Program for Leading Universities & Students (BK21 PLUS)

  19. Notch Antennas

    NASA Technical Reports Server (NTRS)

    Lee, Richard Q.

    2004-01-01

    Notch antennas, also known as the tapered slot antenna (TSA), have been the topics of research for decades. TSA has demonstrated multi-octave bandwidth, moderate gain (7 to 10 dB), and symmetric E- and H- plane beam patterns and can be used for many different applications. This chapter summarizes the research activities on notch antennas over the past decade with emphasis on their most recent advances and applications. This chapter begins with some discussions on the designs of single TSA; then follows with detailed discussions of issues associated with TSA designs and performance characteristics. To conclude the chapter, some recent developments in TSA arrays and their applications are highlighted.

  20. ICRF scenarios for ITER's half-field phase

    SciTech Connect

    Lerche, E.; Van Eester, D.; Ongena, J.; Johnson, T.; Hellsten, T.; Bilato, R.; Czarnecka, A.; Dumont, R.; Krasilnikov, A.; Maslov, M.; Vdovin, V.

    2011-12-23

    The non-active operation phase of ITER will be done in H and {sup 4}He plasmas at half the nominal magnetic field, B{sub 0} = 2.65T. At this field and for the given frequency range of the ICRF system (f = 40-55MHz), three ICRF heating scenarios are available a priori: (i) Fundamental ICRH of majority H plasmas at f{approx_equal}40MHz,(ii) second harmonic (N= 2) {sup 3}He ICRH in H plasmas at f{approx_equal}53MHz and (iii) fundamental minority H heating in {sup 4}He plasmas at f{approx_equal}40MHz. While the latter is expected to perform well for not too large H concentrations, the heating scenarios available for the Hydrogen plasmas are less robust. Recent JET experiments performed in similar conditions to those expected in ITER's half-field phase confirmed the low performance of these two scenarios and numerical simulations have shown that the situation is not much improved in ITER, mainly because of the rather modest plasma temperature and density expected in its initial operation phase. A summary of the main experimental results obtained at JET followed by numerical predictions for ITER's half-field ICRF heating scenarios will be presented.

  1. High-power ICRF and LHCD experiments on Tore Supra

    SciTech Connect

    Saoutic, B.; Beaumont, B.; Becoulet, A.; Bizarro, J.P.; Fraboulet, D.; Garbet, X.; Goniche, M.; Guiziou, L.; Hoang, G.T.; Hutter, T.; Joffrin, E.; Kuus, H.; Litaudon, X.; Mollard, P.; Moreau, D.; Nguyen, F.; Pecquet, A.L.; Peysson, Y.; Rey, G.; van Houtte, D.; Zabiego, M. )

    1994-10-15

    For a given ICRF power, the sawtooth-free period duration increases with plama density. This trend, correlated with an increasing soft X-ray inversion radius, clearly shows a better stabilization by hot ions at higher density. A tentative explanation is given through a full modeling of the hot ion anisotropy using a Fokker Planck code coupled with a 1/2 D power balance code simulating experimental data. A linear stability analysis of the kink/tearing m=1 mode, in terms of a MHD kinetic functional, shows that the anisotropy of the distribution function may amplify the effect of the hot ion pressure gradient. A two-fold lengthening of the sawtooth-free period is obtained when applying LHCD to ICRF heated plasmas. Analysis of polarimetric data shows that, instead of the continuous decrease of the central safety factor observed when using ICRF alone, the q value freezes'' when LHCD power exceeds 3 MW. This demonstrates a current profile control effect opening the way towards steady-state stabilization. Working with both ICRH and LHCD on the same target plasma allows thorough comparisons of transport with different power deposition profiles and coupling mechanisms. The energy stored in electrons is the same although the electronic temperature gradients are quite different. Nevertheless, due to better ion heating, the energy life time (discarding hot ions contribution) is always higher with ICRH. Local transport analyses allow comparisons between both heating schemes for different confinement situations.

  2. High Power RF Transmitters for ICRF Applications on EAST

    NASA Astrophysics Data System (ADS)

    Mao, Yuzhou; Yuan, Shuai; Zhao, Yanping; Zhang, Xinjun; Chen, Gen; Kumazawa, R.; Cheng, Yan; Wang, Lei; Ju, Songqing; Deng, Xu; Qin, Chengming; Yang, Lei

    2013-03-01

    An Ion Cyclotron Range of Frequency (ICRF) system with a radio frequency (RF) power of 4 × 1.5 MW was developed for the Experimental Advanced Superconducting Tokamak (EAST). High RF power transmitters were designed as a part of the research and development (R&D) for an ICRF system with long pulse operation at megawatt levels in a frequency range of 25 MHz to 70 MHz. Studies presented in this paper cover the following parts of the high power transmitter: the three staged high power amplifier, which is composed of a 5 kW wideband solid state amplifier, a 100 kW tetrode drive stage amplifier and a 1.5 MW tetrode final stage amplifier, and the DC high voltage power supply (HVPS). Based on engineering design and static examinations, the RF transmitters were tested using a matched dummy load where an RF output power of 1.5 MW was achieved. The transmitters provide 6 MW RF power in primary phase and will reach a level up to 12 MW after a later upgrade. The transmitters performed successfully in stable operations in EAST and HT-7 devices. Up to 1.8 MW of RF power was injected into plasmas in EAST ICRF heating experiments during the 2010 autumn campaign and plasma performance was greatly improved.

  3. High Harmonic Fast Wave Propagation and Heating on NSTX

    NASA Astrophysics Data System (ADS)

    Parker, J. B.; Phillips, C. K.; Hosea, J. C.; Valeo, E. J.; Wilson, J. R.; Harvey, R. W.

    2007-11-01

    Recent experiments on the National Spherical Torus Experiment (NSTX) show that the high harmonic fast wave (HHFW) core heating efficiency depends on the antenna phasing and plasma conditions. [1]. Power losses in the edge due to rf sheath formation or other parasitic absorption processes could occur if the waves propagate nearly parallel to the wall in the edge regions and intersect nearby vessel structures. To investigate this possibility, the 3D HHFW propagation in NSTX has been studied both analytically and numerically with the ray tracing code GENRAY. Initial calculations show that for certain values of the launched parallel wave number and magnetic field, the waves in NSTX are launched at a shallow angle to the vessel wall. In contrast, for ICRF heating in C-Mod or ITER, the initial ray trajectories tend to be more radially oriented. Comparisons of the GENRAY results with 2D TORIC full wave simulations for the power deposition will also be discussed. [1] See invited talk by J. C. Hosea this meeting.

  4. Operational Experience with the Scattering Matrix Arc Detection System on the JET ITER-Like Antenna

    NASA Astrophysics Data System (ADS)

    Vrancken, M.; Lerche, E.; Blackman, T.; Dumortier, P.; Durodié, F.; Evrard, M.; Goulding, R. H.; Graham, M.; Huygen, S.; Jacquet, P.; Kaye, A.; Mayoral, M.-L.; Nightingale, M. P. S.; Ongena, J.; Van Eester, D.; Van Schoor, M.; Vervier, M.; Weynants, R.

    2009-11-01

    The Scattering Matrix Arc Detection System (SMAD) has been fully deployed on all 4 sets of Resonant Double Loop (RDL), Vacuum Transmission Line (VTL) and Antenna Pressurised Transmission Lines (APTL) of the JET ICRF ITER-Like Antenna (ILA) and this has been indispensable for operating at low (real) T-point impedance values to investigate ELM tolerance. This paper describes the necessity of the SMAD vs VSWR (Voltage Standing Wave Ratio) protection system, SMAD commissioning, problems and a number of typical events detected by the SMAD system during operation on plasma.

  5. Operational Experience with the Scattering Matrix Arc Detection System on the JET ITER-Like Antenna

    SciTech Connect

    Vrancken, M.; Lerche, E.; Dumortier, P.; Durodie, F.; Evrard, M.; Huygen, S.; Ongena, J.; Van Eester, D.; Van Schoor, M.; Vervier, M.; Weynants, R.

    2009-11-26

    The Scattering Matrix Arc Detection System (SMAD) has been fully deployed on all 4 sets of Resonant Double Loop (RDL), Vacuum Transmission Line (VTL) and Antenna Pressurised Transmission Lines (APTL) of the JET ICRF ITER-Like Antenna (ILA) and this has been indispensable for operating at low (real) T-point impedance values to investigate ELM tolerance. This paper describes the necessity of the SMAD vs VSWR (Voltage Standing Wave Ratio) protection system, SMAD commissioning, problems and a number of typical events detected by the SMAD system during operation on plasma.

  6. Correlation between excitation of Alfv{acute e}n modes and degradation of ICRF heating efficiency in TFTR

    SciTech Connect

    Bernabei, S.; Chang, Z.; Darrow, D.; Fredrickson, E.D.; Fu, G.Y.; Hoang, G.T.; Hosea, J.C.; Majeski, R.; Phillips, C.K.; Rogers, J.H.; Schilling, G.; Wilson, J.R.

    1997-04-01

    Alfv{acute e}n modes are excited by energetic ions in TFTR during intense minority ICRF heating. There is a clear threshold in rf power above which the modes are distabilized. The net effect of these modes is the increase of the fast ion losses, with an associated saturation of the ion tail energy and of the efficiency of the heating. Typically, several modes are excited with progressive n-numbers, with frequencies in the neighborhood of 200 kHz. Results suggest that Energetic Particle Modes (EPM), mostly unseen by the Mirnov coils, are generated near the center and are responsible for the ion losses. Stronger global TAE modes, which are destabilized by the stream of displaced fast ions, appear responsible only for minor losses. {copyright} {ital 1997 American Institute of Physics.}

  7. Spacecraft Antennas

    NASA Technical Reports Server (NTRS)

    Jamnejad, Vahraz; Manshadi, Farzin; Rahmat-Samii, Yahya; Cramer, Paul

    1990-01-01

    Some of the various categories of issues that must be considered in the selection and design of spacecraft antennas for a Personal Access Satellite System (PASS) are addressed, and parametric studies for some of the antenna concepts to help the system designer in making the most appropriate antenna choice with regards to weight, size, and complexity, etc. are provided. The question of appropriate polarization for the spacecraft as well as for the User Terminal Antenna required particular attention and was studied in some depth. Circular polarization seems to be the favored outcome of this study. Another problem that has generally been a complicating factor in designing the multiple beam reflector antennas, is the type of feeds (single vs. multiple element and overlapping vs. non-overlapping clusters) needed for generating the beams. This choice is dependent on certain system design factors, such as the required frequency reuse, acceptable interbeam isolation, antenna efficiency, number of beams scanned, and beam-forming network (BFN) complexity. This issue is partially addressed, but is not completely resolved. Indications are that it may be possible to use relatively simple non-overlapping clusters of only a few elements, unless a large frequency reuse and very stringent isolation levels are required.

  8. Response to ICRF-159 in cell lines resistant to cleavable complex-forming topoisomerase II inhibitors.

    PubMed Central

    Davies, S. L.; Bergh, J.; Harris, A. L.; Hickson, I. D.

    1997-01-01

    We have studied the relationship between expression of genes implicated in mediating resistance to cleavable complex-forming topoisomerase II (topo II) inhibitors and cellular sensitivity to ICRF-159, a 'catalytic' inhibitor of topo II. Overexpression of the membrane transporters, P-glycoprotein and multidrug resistance-related protein (MRP), or down-regulation of topo IIalpha and/or -beta, did not confer ICRF-159 resistance. Indeed, marked topo IIalpha down-regulation appeared to be associated with collateral sensitivity to ICRF-159. Our results indicate that the resistance mechanisms that pertain to cleavable complex-forming topo II inhibitors and ICRF-159 are distinct. The evidence presented here suggests that topo IIalpha, not topo IIbeta, is more likely to be the major in vivo target for ICRF-159. Images Figure 1 Figure 2 PMID:9062401

  9. ICRF heating in reactor grade plasmas

    SciTech Connect

    Jacquinot, J.; Bhatnagar, V.P.; Bures, M.; Cottrell, G.A.; Eriksson, L.G.; Sack, C.H.; Start, D.F.H.; Taroni, A. ); Hellsten, T. ); Koch, R. ); Moreau, D. )

    1990-01-01

    Impurity influxes in JET discharges due to ICRH have been reduced to insignificant levels. This has allowed high quality H-modes to be produced with ICRH alone and has enhanced the density limit which is now the same as the NBI limit. Improvement in the deuterium fuel fraction has led to the generation of 100kW of non thermal {sup 3}He-D fusion power. Alpha-particle simulations using MeV ions created by ICRH show classical energy loss and suggest that {alpha}-heating in a reactor will be highly efficient. A clear demonstration of TTMP damping of the fast wave in high beta plasmas has been achieved. A broadband ICRH system is proposed for NET/ITER which will allow fast wave current drive and central ion heating for burn control and ignition. 10 refs., 6 figs.

  10. Antenna theory and design

    NASA Astrophysics Data System (ADS)

    Stutzman, W. L.; Thiele, G. A.

    Antenna fundamentals and definitions are examined, taking into account electromagnetic fundamentals, the solution of Maxwell's equations for radiation problems, the ideal dipole, the radiation pattern, directivity and gain, reciprocity and antenna pattern measurements, antenna impedance and radiation efficiency, antenna polarization, antennas in communication links and radar, and the receiving properties of antennas. Some simple radiating systems are considered along with arrays, line sources, wire antennas, broadband antennas, moment methods, and aperture antennas. High-frequency methods and aspects of antenna synthesis are discussed, giving attention to geometrical optics, physical optics, wedge diffraction theory, the ray-fixed coordinate system, the cylindrical parabolic antenna, and linear array methods.