G. H. Jones

Oak Ridge National Laboratory, Oak Ridge, Florida, United States

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Publications (16)1 Total impact

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    ABSTRACT: Fabrication and assembly of a High Power Prototype (HPP) of the JET ITER-like Ion Cyclotron Range of Frequencies (ICRF) launcher have been completed at Oak Ridge National Laboratory (ORNL), and high power tests have begun. The HPP consists of one quadrant of the full 7.5 MW antenna (1). The prototype is the product of a collaboration between ORNL, Princeton Plasma Physics Laboratory, and EFDA-JET/UKAEA. Internal matching capacitors are utilized in a circuit that maintains a voltage standing wave ratio (VSWR) at the input 45 kV peak voltage at the internal matching capacitors, which is greater than the original design voltage. High power pulses up to 2s have been run. Diagnostics include thermocouples, voltage probes at the capacitors and along the integral lambda/4 matching transformer, and an optical temperature sensor for in-situ measurements of capacitor temperatures. Low power measurements of electrical characteristics of the antenna have been made and compared with a 3-D electromagnetic model.
    12/2003;
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    ABSTRACT: Power handling tests have been conducted on the High Power Prototype (HPP) of the JET ITER-Like Ion Cyclotron Resonance Heating Antenna, constructed and tested in a joint collaboration between Oak Ridge National Laboratory, Princeton Plasma Physics Laboratory, and EFDA-JET/UKAEA. The antenna has been operated at a maximum voltage >45 kV peak for short (.05s) pulses at 42.5 MHz and 50 MHz. Long pulse tests are just beginning with pulse lengths of 2 s achieved to date. Temperature measurements made during short pulse tests at 400 kW peak power (900-1800 W average) at the non-actively cooled ends of the two internal matching capacitors indicate a temperature rise of 20 ^oC over a 3 hour operating period. The latest results will be shown. The impact of HPP results on the design of the final JET ITER-Like ICRH Antenna will be discussed.
    10/2003;
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    ABSTRACT: The National Compact Stellarator Experiment (NCSX) [http://www.pppl.gov/ncsx/Meetings/CDR/CDRFinal/EngineeringOverview_R2.pdf] is being designed as a proof of principal test of a quasi-axisymmetric compact stellarator. This concept combines the high beta and good confinement features of an advanced tokamak with the low current, disruption-free characteristics of a stellarator. NCSX has a three-field-period plasma configuration with an average major radius of 1.4 m, an average minor radius of 0.33 m and a toroidal magnetic field on axis of up to 2 T. The stellarator core is a complex assembly of four coil systems that surround the highly shaped plasma and vacuum vessel. Heating is provided by up to four, 1.5 MW neutral beam injectors and provision is made to add 6 MW of ICRH. The experiment will be built at the Princeton Plasma Physics Laboratory, with first plasma expected in 2007.
    Fusion Engineering and Design. 01/2003;
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    ABSTRACT: The paper reports on the status of the JET ITER-Like ICRF Antenna project and highlights main challenges that have come up during its design phase.
    01/2003;
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    ABSTRACT: : A High Power Prototype (HPP) of the JET ITER-like Ion Cyclotron Range of Frequencies (ICRF) launcher is now being fabricated at Oak Ridge National Laboratory and Princeton Plasma Physics Laboratory. The HPP consists of one quadrant of the full 7.5 MW JET-EP ICRF antenna. Internal matching capacitors are utilized in a circuit that maintains a voltage standing wave ratio (VSWR) at the input < 1.5 over a factor of ten range in resistive loading. The HPP will be tested in vacuum at full capacitor design voltage (35 kV peak) and current (1.25 kA RMS) for 10s pulses. The status of the HPP fabrication and assembly tasks will be reviewed. In addition, the set of diagnostics for measurement of currents, voltages, input impedance, and temperatures (including in-situ optical measurements of the capacitor braze-joint temperatures), will be discussed. Finally, a detailed description of the test plan for the HPP will be presented.
    11/2002;
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    ABSTRACT: The engineering design status of the Quasi-Poloidal Stellarator Experiment (QPS) is presented. The purpose, configuration, and possible manufacturing and assembly techniques of the various components of the core are described.
    Fusion Engineering, 2002. 19th Symposium on; 02/2002
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    ABSTRACT: 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.
    01/2001;
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    ABSTRACT: The tokamak radiation shielding includes the neutron and gamma shielding around the torus and penetrations required to (1) limit activation of components outside the shield to levels that permit hands-on maintenance and (2) limit the nuclear heating of the superconducting coils and cold structure. The primary design drivers are space, the 350°C bakeout temperature, and cost; therefore, different shield materials were used for different shield components and locations. The shielding is divided into three areas: (1) torus shielding around the vacuum vessel, (2) duct shielding around the vacuum pumping ducts and vertical diagnostic ducts, and (3) penetration shielding in and around the radial ports. The major shield components include water between the walls of the vacuum vessel, lead monosilicate/boron carbide tiles that are attached to the exterior of the vacuum vessel, shield plugs that fill the openings of the large radial ports, and polyethylene/lead/boron shield blocks for duct shielding. A description of the shielding configuration and the performance and operational requirements will be discussed
    Fusion Engineering, 1993., 15th IEEE/NPSS Symposium on; 11/1993
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    ABSTRACT: The design of the lower hybrid launcher is configured to couple 1.5 MW of steady state lower hybrid heating/lower hybrid current drive (LHH/LHCD) power at 3.7 GHz to the Tokamak Physics Experiment (TPX) plasma. The launcher utilizes a unique laminated, water-cooled construction to achieve a compact array of 128 waveguides at the grille surface and includes real-time position control for plasma coupling. The design features of this launcher are described with details of the principal components and the possible upgrade of the launcher to 3 MW. Results of steady state thermal analysis of the launcher grille septa are included
    Fusion Engineering, 1993., 15th IEEE/NPSS Symposium on; 11/1993
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    ABSTRACT: The conceptual design of the TPX vacuum pumping system is presented. The baseline concept includes a high vacuum pumping system, a roughing and backing system, volume pumping ducts, a leak detection system, a diagnostic pumping system, and a cryostat pumping system. The high vacuum pumping system will initially evacuate the torus, provide pumping of the diverters during operation, and provide pumping for glow discharge cleaning. The high vacuum pumping system has high throughput and variable conductance capabilities and includes cryocondensation pumps for pumping deuterium during normal operation as well as turbomolecular pumps for pumping helium and for glow discharge cleaning. Sixteen vacuum ducts extend from the vacuum vessel through the cryostat to the pumping system; each duct contains a torus isolation valve and an electrical break. Butterfly valves at the cryopump inlets will be used for throttling the pumps and for pump regeneration. In this way, half of the pumps can be regenerated while the others are operating. The specific design parameters and predicted performance of the vacuum pumping system are discussed, as are the upgrade options for steady state and DT operation
    Fusion Engineering, 1993., 15th IEEE/NPSS Symposium on; 11/1993
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    ABSTRACT: The Tokamak Physics Experiment is designed to develop the scientific basis for a compact and continuously operating tokamak fusion reactor. It is based on an emerging class of tokamak operating modes, characterized by beta limits well in excess of the Troyon limit, confinement scaling well in excess of H-mode, and bootstrap current fractions approaching unity. Such modes are attainable through the use of advanced, steady state plasma controls including strong shaping, current profile control, and active particle recycling control. Key design features of the TPX are superconducting toroidal and poloidal field coils; actively-cooled plasma-facing components; a flexible heating and current drive system; and a spacious divertor for flexibility. Substantial deuterium plasma operation is made possible with an in-vessel remote maintenance system, a lowactivation titanium vacuum vessel, and shielding of ex-vessel components. The facility will be constructed as a national project with substantial participation by U.S. industry. Operation will begin with first plasma in the year 2000.
    Journal of Fusion Energy 01/1993; 12(3):221-258. · 1.00 Impact Factor
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    ABSTRACT: A proposal has been made to improve the performance of ITER (International Thermonuclear Experimental Reactor) by modifying the reference design point. The high-aspect-ratio design (HARD) proposal increases the aspect ratio to four, increases the central toroidal field to 7 T, and decreases the peak plasma current to 14.8 MA. Systems studies indicate that the HARD parameters provide improved technology testing capability by increasing the neutron wall loading while maintaining the CDA (conceptual design activity) physics constraints. Changes in configuration, loading, stresses, and other factors for the containment structure components, based on the HARD parameters, have been investigated. In general, the HARD configuration has only minor effects on the containment structures. Advantages include better distribution of resistance and lower loads and stresses for the vacuum vessel. Disadvantages include much higher electromagnetic loads on the inboard blankets, less margin in the stability parameter, and the requirement to put passive loops on the inboard blankets. No significant change in cost would be expected
    Fusion Engineering, 1991. Proceedings., 14th IEEE/NPSS Symposium on; 11/1991
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    ABSTRACT: Several designs that address plasma-facing plate configurations and thermal-hydraulic design issues have been developed for the ITER (International Thermonuclear Experimental Reactor) divertor. Design criteria growing out of physics requirements, physical constraints, and remote handling requirements impose severe mechanical requirements on the support structure and its attachments. The authors discuss the design criteria for the divertor mounting structure and identify the mechanical design issues that need to be addressed. Achieving the criteria may require the development of new components and innovative configurations, specifically a new class of remote fasteners and electrically resistant material for mounts. The possible design of such components and an R&D program to develop them are described, and issues specific to the high-aspect-ratio design (HARD) configuration are summarized. Analysis and experiments that will resolve these issues and concerns and lead to a final ITER design are identified
    Fusion Engineering, 1991. Proceedings., 14th IEEE/NPSS Symposium on; 01/1991
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    ABSTRACT: The Tokamak Physics Experiment is designed to develop the scientific basis for a compact and continuously operating tokamak fusion reactor. It is based on an emerging class of tokamak operating modes, characterized by beta limits well in excess of the Troyon limit, confinement scaling well in excess of H-mode, and bootstrap current fractions approaching unity. Such modes are attainable through the use of advanced, steady state plasma controls including strong shaping, current profile control, and active particle recycling control. Key design features of the TPX are superconducting toroidal and poloidal fields coils; actively-cooled plasma-facing components; a flexible heating and current drive system; and a spacious divertor for flexibility. Substantial deuterium plasma operation is made possible with an in-vessel remote maintenance system, a low-activation titanium vacuum vessel, and shielding of ex-vessel components. The facility will be constructed as a national project with substantial participation by U.S. industry. Operation will begin with first plasma in the year 2000.
    Journal of Fusion Energy. 12(3):221-258.
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    ABSTRACT: A high power prototype (HPP) of the JET ITER-Like ICRF Antenna has been built and tested in a joint effort by ORNL, PPPL, ERM/KMS, and EFDA-JET. For the first time, high power vacuum tests have been performed on an antenna with features similar to those found in the current ITER antenna design. Advances include a new matching network using internal capacitors that is insensitive to target plasma characteristics, and increased power density to minimize the amount of port space required. Three-dimensional electromagnetic modeling has been used extensively to improve the antenna design and assist in interpretation of test results. During the HPP tests, capacitor voltages greater than 45 kV were achieved for short (0.05s) pulses. Voltages greater than 35 kV, approximately the voltage needed to couple the full 7.2 MW design power into most JET plasmas, were sustained for moderate length (~0.5 s) pulses. Long (10s) pulse operation was limited by excessive heating in localized regions due to rf dissipation, a problem that will be corrected in the final antenna. In this paper test results, associated numerical modeling, and their impact on the design of the final device will be reviewed.
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    ABSTRACT: A High Power Prototype (HPP) of the JET ITER-like ion cyclotron resonance heating (ICRH) antenna has been constructed and tested in a joint collaboration between Oak Ridge National Laboratory, Princeton Plasma Physics Laboratory, and EFDA-JET/UKAEA. The HPP consists of one quadrant of the full JET-EP ICRH antenna. Internal matching capacitors are utilized in a circuit that maintains a voltage standing wave ratio at the input < 1.5 over a factor of ten range in resistive loading. The HPP is being tested in vacuum at full capacitor design voltage and current for up to 10-s pulses. The HPP design and status of the test results will be reviewed. Measurements of the currents, voltages, input impedance, and temperatures will be discussed including low power measurements of the tuning range and sensitivity to capacitor position. Measurements will be compared to circuit analysis and modeling codes. The impact of HPP results on the design of the final JET ITER-like ICRH antenna will be discussed.