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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic island control on the Compact Auburn Torsatronf| (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1576-1582 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The understanding and control of magnetic islands is an important issue in confinement of toroidal plasmas. A series of recent experiments on the Compact Auburn Torsatron (CAT) [Fusion Technol. 18, 281 (1990)] have investigated the control of magnetic islands. As a by-product, the minimization of the size of magnetic islands has been accomplished through the application of externally applied error fields. Both the phase and amplitude of the applied correction field at a given rational surface are varied in order to control the island chain on a rational surface. The experimental results have been interpreted within the framework of a Hamiltonian description of the magnetic field in toroidal geometry. In particular it has been demonstrated that first order perturbation theory is sufficient to predict the variation of island size for a wide range of externally applied fields. Using this theoretical approach a novel technique of error field determination through the measurement of the local rotational transform has been developed. The physical mechanisms which lead to spatial spreading of the electron beam used in the surface mapping have also been studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870709
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  • 2
    Electronic Resource
    Electronic Resource
    Drift surface axis position and transform measurements in the Compact Auburn Torsatron (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 1270-1273 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In toroidal plasma confinement devices, the highly energetic fusion products will have trajectories defining drift surfaces that deviate considerably from the magnetic surfaces. An understanding of these drift surfaces is important for efficient operation of a fusion reactor. By appropriate choice of electron energy on the Compact Auburn Torsatron [Fusion Technol. 18, 281 (1990)], normalized drift surface shifts similar to those for fusion products in a reactor can be studied. As a benchmark, a set of experiments have been conducted to study the axis position and central rotational transform associated with varying vertical fields. Corresponding experiments have been conducted which measure the axis position and central transform associated with the drift surfaces of highly energetic electrons. These experiments were compared and a theoretical model incorporating the spatial nonuniformity of the applied vertical magnetic field was developed. The experimental results agreed well with this theory. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871338
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  • 3
    Electronic Resource
    Electronic Resource
    Observation and analysis of particle drift islands in a torsatron (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2877-2879 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic islands in toroidal plasma confinement devices are generated by resonant magnetic error fields. Energetic particle drift surfaces can differ substantially from magnetic flux surfaces. In this Letter the first direct measurement of islands in energetic particle drift surfaces are presented. The understanding of these drift islands is important for the optimization of plasma confinement. These drift islands are demonstrated to form in energetic electron drift surfaces as a result of resonant magnetic field perturbations and resonant, applied electric field perturbations. The results, once corrected for inherent magnetic error fields, agree well with theoretical predictions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871187
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  • 4
    Electronic Resource
    Electronic Resource
    Electron transport studies in stochastic magnetic fields on the Compact Auburn Torsatron (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2026-2032 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A steady-state source of electrons was installed in the Compact Auburn Torsatron (CAT) [Fusion Technol. 18, 28 (1990)]. The transport of the electrons was studied with externally applied resonant magnetic fields. Magnetic fields with primary modes n/m=1/4 and n/m=1/3, and average radial field amplitude 〈(br/Bφ)rms〉∼1% have been employed. The perturbation fields produced mixed islands and stochastic regions at the outer region of the CAT torsatron. The particle diffusion coefficient was measured and compared to stochastic transport models. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871290
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  • 5
    Electronic Resource
    Electronic Resource
    New techniques of magnetic surface measurement on the compact Auburn torsatron : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 464-466 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Torsatron and stellarator plasma devices rely on magnetic surface mapping to verify the detailed vacuum magnetic field structure. Two new techniques of magnetic surface mapping are under development on the compact Auburn torsatron. The first is a fast-rotating fluorescent wire (FRFW) system. Compared with the usual fluorescent screen, fluorescent rod, or the capacitive point probe techniques, the FRFW system has the advantage of greatly increasing the number of detectable toroidal transits and of minimizing surface mapping time. The second technique is a resistive wire system which provides an alternative fast-field mapping method. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146384
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetic surface mapping with an emissive filament technique on the Auburn torsatron (1987)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 509-515 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Torsatron and stellarator plasma confinement devices rely on magnetic surface mapping to determine the critical vacuum magnetic field structure. A recently developed method employing an emissive filament offers some advantages over the traditional technique of mapping with a directed electron beam. On the Auburn torsatron a comparative study between the emissive filament and directed electron beam techniques has been conducted. The parameters varied in the comparative study are filament geometry, emission current, bias voltage, background gas pressure, and magnetic field strength. This comparative study indicates that the emissive filament technique is reliable over a broad and easily accessible range of parameters. We have also measured the spatial distribution of electrons on a given magnetic surface. As an application of the emissive filament technique, the optimization of the magnetic surfaces on the Auburn torsatron is shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139261
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic surface mapping with highly transparent screens on the Auburn torsatron (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 460-466 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In stellarator-type magnetic confinement devices (of which the torsatron is one), the magnetic field is produced entirely by external, current-carrying coils. Two methods for mapping magnetic surfaces in the Auburn torsatron were tested and compared, both of which involve the use of highly transparent screens. The first method consists of coating the screen with a phosphor that emits light when struck by electrons emitted by an electron gun. A pattern representative of a magnetic surface is formed on the screen, and this pattern is recorded photographically. The second method uses an uncoated screen to collect electrons emitted from an emissive probe, which is scanned over a poloidal cross section of the torus. Under certain conditions, the collected current is a constant over a particular magnetic surface so that a contour plot of the current versus position is equivalent to a plot of the magnetic surfaces. Parametric studies of the two methods are presented, and the effectiveness of each technique is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139861
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  • 8
    Electronic Resource
    Electronic Resource
    An experimental study of magnetic islands as Hamiltonian systems (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 4384-4390 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic islands play an important role in determining plasma transport in toroidal magnetic confinement systems. The magnetic error fields and the associated islands can be theoretically described by a Hamiltonian approach. Experiments have been conducted on the Compact Auburn Torsatron [Fusion Technol. 18, 281 (1990)] to test the applicability and limits of the first-order Hamiltonian theory to magnetic islands. A novel set of helical trim coils with the same spatial periodicity as an ι– = 1/2 magnetic island were used to create a perturbation field of variable magnitude and phase. Extensive experimental parametric studies of the magnetic island were conducted and compared with theory. It was found that the first-order Hamiltonian theory is applicable for the complete range of experimental error fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860556
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