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Languages : en
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The dual-strap Tore Supra ICRF antennas have been very successful in coupling high power fluxes> 16 MW/m2 to the plasma. In many cases it has been found that the power is limited not by the voltages and currents that can be sustained on antenna components, but rather by localized increases in antenna surface temperatures which are correlated with increased impurity levels. Hot spots have been observed using an IR imaging system with peak temperatures as high as 1,100 C after 2 s, and as little as 1.5 MW power coupled from a single launcher. The maximum temperature observed is highly dependent on antenna phasing, and is lowest with dipole ([pi]) phasing of the relative antenna currents. Both toroidal and poloidal asymmetries in hot spot distribution have been observed, and interestingly, the toroidal asymmetry has been found to vary when the phase is changed from+[pi]/2 to[minus][pi]/2. Significant differences in the temperature profiles have been seen on the two types of Faraday shield in use, which appears to be related to the fact that one type has a recessed center septum between straps while the other does not. In some cases, the peak temperature has been observed to increase as the antenna/plasma gap is increased, while the peak remains in the same location. This behavior suggests that voltages generated by currents flowing in the Faraday shield structure itself may play a role in generating potentials responsible for the hot spots, in addition to rf fields in the plasma. In this paper data on antenna surface heating and loading data as a function of plasma density, antenna/plasma gap, and phasing will be presented. Calculations from the RANT3D electromagnetic code together with bench measurements of electric fields near the antenna surface will also be shown.
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Languages : en
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Book Description
The dual-strap Tore Supra ICRF antennas have been very successful in coupling high power fluxes> 16 MW/m2 to the plasma. In many cases it has been found that the power is limited not by the voltages and currents that can be sustained on antenna components, but rather by localized increases in antenna surface temperatures which are correlated with increased impurity levels. Hot spots have been observed using an IR imaging system with peak temperatures as high as 1,100 C after 2 s, and as little as 1.5 MW power coupled from a single launcher. The maximum temperature observed is highly dependent on antenna phasing, and is lowest with dipole ([pi]) phasing of the relative antenna currents. Both toroidal and poloidal asymmetries in hot spot distribution have been observed, and interestingly, the toroidal asymmetry has been found to vary when the phase is changed from+[pi]/2 to[minus][pi]/2. Significant differences in the temperature profiles have been seen on the two types of Faraday shield in use, which appears to be related to the fact that one type has a recessed center septum between straps while the other does not. In some cases, the peak temperature has been observed to increase as the antenna/plasma gap is increased, while the peak remains in the same location. This behavior suggests that voltages generated by currents flowing in the Faraday shield structure itself may play a role in generating potentials responsible for the hot spots, in addition to rf fields in the plasma. In this paper data on antenna surface heating and loading data as a function of plasma density, antenna/plasma gap, and phasing will be presented. Calculations from the RANT3D electromagnetic code together with bench measurements of electric fields near the antenna surface will also be shown.
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Category :
Languages : en
Pages : 16
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Book Description
The edge plasma interactions of the actively cooled radio-frequency heating launchers in Tore Supra- ion-cyclotron range-of-frequencies (ICRF) antennas and lower-hybrid (LH) grills-are studied using infrared video imaging. On the two-strap ICRF antennas, operated in fast-wave electron heating or current drive mode, hot spots with temperatures of 500-900° C are observed by the end of 2-s power pulses of 2 MW per antenna. The distribution and maximum values of temperature are determined principally by the relative phase of the two antenna straps: dipole (heating) phasing results in significantly less antenna heating than does 90' (current drive) phasing. Transient heat fluxes of 1-20 MW/m2 are measured on the lateral protection bumpers at ICRF turn-on; these fluxes are primarily a function of plasma and radio frequency (rf) control, and are not simply correlated with the strap phasing or the final surface temperature distributions. The remarkable feature of the lower hybrid edge interaction is the production of beams of heat flux in front of the grills; these beams propagate along the helical magnetic field lines and can deliver fluxes of 5-10 MW/m2 over areas of several cm2 to plasma-facing components such as the grill or antenna lateral bumpers. Both the ICRF and LH phenomena appear to result from the acceleration of particles by the near fields of the launchers. Modeling of the heat flux deposition on components and its relation to sputtering processes is presented, and possibilities for controlling these interactions are discussed.
Author: Philip M. Ryan
Publisher: American Institute of Physics
ISBN:
Category : Science
Languages : en
Pages : 554
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Book Description
Clearwater, Florida, 7-9 May 2007
Author: Tak K. Mau
Publisher: American Inst. of Physics
ISBN: 9780735400382
Category : Science
Languages : en
Pages : 570
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Book Description
This proceedings volume includes the most recent research advances in the application of RF power in plasmas, mainly in fusion science. Most papers deal with plasma heating and current drive, profile control, and stabilization using RF techniques, with some on RF sources and launchers. New and exciting results from all major tokamak experiments, and from theory and modeling are included. There is also a paper on RFplasma application in space propulsion by an active NASA astronaut. This book is a valuable reference for the RF researchers in fusion and other disciplines.
Author: Cary B. Forest
Publisher: American Institute of Physics
ISBN:
Category : Science
Languages : en
Pages : 544
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Book Description
Includes the most recent research advances in the application of RF power in plasmas, mainly in fusion science.
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Category :
Languages : en
Pages :
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The Oak Ridge National Laboratory is designing, fabricating, and testing antennas for TFTR and Tore Supra. The antennas will deliver 4 MW per port to the hot plasma. The antennas' designs are nearly complete; they are backed by the results of extensive modeling, analyses, and tests of the electrical, thermal, and structural characteristics of the antennas that were carried out during the design process.
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Category :
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category : Power resources
Languages : en
Pages : 782
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Author: Stephen J. Wukitch
Publisher:
ISBN:
Category :
Languages : en
Pages : 40
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Book Description
In Alcator C-Mod, we have investigated the compatibility of high power ion cyclotron range of frequencies antenna with high performance plasmas and all high-Z plasma facing components, to provide operational information for future devices such as ITER. Boronization appears to be critical achieving low radiated power plasmas and is eroded rapidly such that the best performance is lost when the integrated injected RF energy reaches ~50 MJ. Since Ohmic H-modes with similar integrated input energy show a significantly slower degradation, an RF erosion mechanism is playing a significant role. RF-enhanced sheaths on flux tubes connected from the antennas to the top of the outer divertor are the most likely erosion mechanism. Antenna operation without a Faraday screen was found to degrade antenna performance through increased impurity sources.
Author: Tak K. Mau
Publisher: American Institute of Physics
ISBN:
Category : Medical
Languages : en
Pages : 568
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Book Description
This proceedings volume includes the most recent research advances in the application of RF power in plasmas, mainly in fusion science. Most papers deal with plasma heating and current drive, profile control, and stabilization using RF techniques, with some on RF sources and launchers. New and exciting results from all major tokamak experiments, and from theory and modeling are included. There is also a paper on RFplasma application in space propulsion by an active NASA astronaut. This book is a valuable reference for the RF researchers in fusion and other disciplines.
