Wave-particle Studies in the Ion Cyclotron and Lower Hybrid Range of Frequencies in Alcator C-Mod

Wave-particle Studies in the Ion Cyclotron and Lower Hybrid Range of Frequencies in Alcator C-Mod PDF Author: Paul Bonoli
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ISBN:
Category :
Languages : en
Pages : 202

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(cont.) It is shown that this off-axis LH current drive can be used to create discharges with non-monotonic profiles of the current density and reversed shear. An advanced tokamak operating regime near the ideal no-wall [beta]-limit is described for C-Mod, where about 70% of the current is driven through the bootstrap effect. The LH power is coupled to C-Mod through a waveguide launcher consisting of four rows (vertically) with 24 guides per row (toroidally). A detailed description of the LH launcher fabrication is given in this paper along with initial operation results.

Wave-particle Studies in the Ion Cyclotron and Lower Hybrid Range of Frequencies in Alcator C-Mod

Wave-particle Studies in the Ion Cyclotron and Lower Hybrid Range of Frequencies in Alcator C-Mod PDF Author: Paul Bonoli
Publisher:
ISBN:
Category :
Languages : en
Pages : 202

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Book Description
(cont.) It is shown that this off-axis LH current drive can be used to create discharges with non-monotonic profiles of the current density and reversed shear. An advanced tokamak operating regime near the ideal no-wall [beta]-limit is described for C-Mod, where about 70% of the current is driven through the bootstrap effect. The LH power is coupled to C-Mod through a waveguide launcher consisting of four rows (vertically) with 24 guides per row (toroidally). A detailed description of the LH launcher fabrication is given in this paper along with initial operation results.

Ion Cyclotron Range of Frequencies Loading Studies on Alcator C-Mod

Ion Cyclotron Range of Frequencies Loading Studies on Alcator C-Mod PDF Author: Alexandre Parisot
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ISBN:
Category :
Languages : en
Pages : 26

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Rapid changes in the loading resistance of fast wave antennas can limit high power operations of heating systems in the Ion Cyclotron Range of Frequencies (ICRF). Although novel matching techniques are being developed to reduce their effects, understanding the physics involved in these variations is of interest to guide and facilitate the design effort. We have studied the dependence of the loading resistance upon plasma parameters for the three ICRF antennas in the Alcator C-Mod tokamak. In contrast with similar studies in JET and Tore Supra, the evanescent decay term was not found to play an important role. The dominant variations could be related to changes in the shape of the electron density profiles in the propagating region. In H-mode, the loading resistance decreases as the density at the top of the pedestal is increased, and increases for higher Scrape-Off Layer densities. This dependency on global plasma parameters is generally identical for the three antennas, up to a proportionality constant, while local changes in front of an individual antennas could explain the residual discrepancy. To link the observations with theory, the surface impedance at the Faraday shield was calculated by solving the wave equation in a slab geometry using experimental radial density profiles. This approach leads to a good agreement with measurements over a wide range of operating conditions in L-mode, ELM-free and EDA H-mode plasmas, and it can be interpreted qualitatively in terms of impedance transformation in the scrape-off layer region. Implications for more complex modeling approaches are also discussed.

Observation and Modeling of Ion Cyclotron Range of Frequencies Waves in the Mode Conversion Region of Alcator C-Mod

Observation and Modeling of Ion Cyclotron Range of Frequencies Waves in the Mode Conversion Region of Alcator C-Mod PDF Author: Yijun Lin
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ISBN:
Category :
Languages : en
Pages : 58

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The fast magnetosonic wave (FW), mode converted ion cyclotron wave (MC ICW) and ion Bernstein wave (MC IBW) have all been observed and unambiguously identified in the mode conversion region of Alcator C-Mod. The influences of the species mix, mode conversion location and Bpol=Btot have been studied in D(3He) plasmas at B0 ~ 5:4 T (fRF = 50 MHz) and B0 ~ 8 T (fRF = 78 MHz). The RF waves were measured by a phase contrast imaging (PCI) system. The experimental observation is compared with the result from a synthetic PCI diagnostic based upon the full wave code TORIC. Good agreement between the observation and modeling has been obtained on the spatial structure of the RF waves. When the mode conversion layer was off axis, both MC ICW and MC IBW were observed. In 5.4 T near axis mode conversion discharges, double hump spatial structure of the MC waves was observed experimentally and reproduced by the synthetic PCI. Such structure is an indication of the up-down asymmetry of the MC ICW. In 8 T near axis mode conversion discharges, we had the first definitive observation of IBW dominated MC in Alcator C-Mod.

The ORNL Fast Wave ICRF (Ion Cyclotron Range of Frequencies) Antenna for Alcator C-Mod

The ORNL Fast Wave ICRF (Ion Cyclotron Range of Frequencies) Antenna for Alcator C-Mod PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 11

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A fast wave ICRF antenna is being designed for Alcator C-Mod which is prototypical in many respects of the baseline launcher design for the Compact Ignition Tokamak (CIT). The C-Mod launcher has a single current strap, with a strap and cavity geometry very similar to one quadrant of the CIT launcher, which has four straps in a 2 x 2 configuration. The antenna fits entirely within an 8 in. wide by 25 in. long port and is radially movable over a distance of 15 cm. It will operate at a frequency of 80 MHz for pulse lengths up to 1 s, at a maximum power level of 2 MW, corresponding to a power flux of>1.5 kW/cm2. The antenna is an end fed double loop configuration in which the current strap is grounded in the middle to provide mechanical support. The design includes a disruption support system which accommodates thermal expansion of the antenna box while supporting large disruption loads. It also includes a novel matching system consisting of an external resonant loop with two shunt capacitors serving as tuning/matching elements. 8 refs., 5 figs., 12 tabs.

Energy Research Abstracts

Energy Research Abstracts PDF Author:
Publisher:
ISBN:
Category : Power resources
Languages : en
Pages : 782

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ICRF [ION CYCLOTRON RANGE OF FREQUENCIES] EDGE MODELING STUDIES.

ICRF [ION CYCLOTRON RANGE OF FREQUENCIES] EDGE MODELING STUDIES. PDF Author: I.S. LEHRMAN.
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ISBN:
Category :
Languages : en
Pages :

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Ultrahigh Resolution Simulations of Mode Converted Ion Cyclotron Waves and Lower Hybrid Waves

Ultrahigh Resolution Simulations of Mode Converted Ion Cyclotron Waves and Lower Hybrid Waves PDF Author: John C. Wright
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ISBN:
Category :
Languages : en
Pages : 16

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FullWave studies of mode conversion (MC) processes in toroidal plasmas have required prohibitive amount of computer resources in the past because of the disparate spatial scales involved. The TORIC code [1] solves the linear sixth order reduced wave equation for the ion cyclotron range of frequencies (ICRF), in toroidal geometry using a Fourier representation for the poloidal dimension and finite elements in the flux dimension. The range of problems that TORIC can do has been extended through both new serial algorithms and parallelization of memory and processing. The implementation of out-of-core memory management, FFT convolutions, and improved memory management brought MC studies just into range of the serial version of the code running on a NERSC Cray SV1. Some simple tests and arguments show that more resolution than is possible on a single processor system is needed to fully resolve these scenarios. By distributing the large linear system across many processors in conjunction with the out-of-core technique, the resolution limitations are effectively removed. ScaLAPACK is used to do the linear algebra operations and message passing interface (MPI) is used to distribute the significant amount of postprocessing. The new parallel version of the code can easily do the most difficult MC problems on present day tokamaks (Alcator C-Mod and Asdex-Upgrade), with only 32 pc from a local Beowulf cluster. Using 48 or more processors admits us to problems in the lower hybrid range of frequencies. Key words: TORIC ICRF FastWave IBW Bernstein LowerHybrid Simulation FullWave. PACS: 52.25. Mq 52.35.H 52.50. Sw 52.65.-y.

Planning for U.S. Ion Cyclotron Heating Research Relevant to the Compact Ignition Tokamak and Alcator C-Mod

Planning for U.S. Ion Cyclotron Heating Research Relevant to the Compact Ignition Tokamak and Alcator C-Mod PDF Author: D. W. Swain
Publisher:
ISBN:
Category :
Languages : en
Pages : 73

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Scientific and Technical Aerospace Reports

Scientific and Technical Aerospace Reports PDF Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 994

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Fast Wave Current Drive in the Ion Cyclotron Range of Frequencies

Fast Wave Current Drive in the Ion Cyclotron Range of Frequencies PDF Author:
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ISBN:
Category : Cyclotron resonance
Languages : en
Pages : 16

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