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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Conceptual design and numerical simulation of a correlation diagnostic for measurement of magnetic fluctuations in plasmas (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1990-1997 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: It has been previously suggested that crossed-sightline correlation of electron cylotron emission might be used to measure magnetic fluctuations in high-temperature plasmas. Reported here are the results of a continuing project to determine under what conditions (if any) this measurement will be feasible. An initial conceptual design for the device hardware has been completed. Large portions of the numerical simulation are working, including ray-tracing and emission/absorption packages. An initial discussion of data analysis for the experimental data is presented, and an analysis of the uncertainty in the line center (magnetic field) measurement in terms of the experimental uncertainties is given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140064
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  • 3
    Electronic Resource
    Electronic Resource
    ECE diagnostic for ATF (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1614-1616 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Electron cyclotron emission (ECE) from the Advanced Toroidal Facility (ATF) torsatron will allow measurement of plasma electron temperature. For low-field operation (0.95 T) the second harmonic is cut off at a relatively low density; therefore, third-harmonic emission from 67 to 83 GHz is used to yield central electron temperatures. At high-field operation (1.9 T) second-harmonic emission from 82 to 114 GHz is optically thick and can provide Te(r) information. A vertical view of the saddle-point geometry of the ATF mod B spatial contours provides a line of sight along which the mod B contours are symmetric with respect to flux surfaces. A single horn–lens viewing beam system with a vertical view is designed to cover the entire 67–114-GHz range, providing a spot size on the order of 6 cm. Radiation will be delivered to one of three waveguide mixers by C-band waveguide. Each of the three mixers covers a 16-GHz segment of the emission spectrum, downconverting it to the 2–18-GHz intermediate-frequency band, where it is processed by a 16-channel array of bandpass filters, providing 1-GHz frequency resolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140163
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    High resolution electron cyclotron emission temperature profile and fluctuation diagnostic for Alcator C-Mod : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1011-1013 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new second harmonic heterodyne electron cyclotron emission system with high spatial resolution (≤15 mm) and a large number of channels (32) for dense profile coverage will be installed on Alcator C-Mod. The system will provide detailed radial electron temperature profiles and core temperature fluctuation measurements. The collection system is composed of elliptical and parabolic mirrors coupled to two overmoded waveguides to provide high poloidal spatial resolution necessary for T˜e measurements. Four radiometer sections cover the frequency range of 234–306 GHz, coupled to four optimized intermediate frequency modules with eight channels of detectors, amplifiers, dividers, and filters providing the profile information. A separate filter arrangement allows for temperature fluctuation measurements utilizing correlation techniques. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149368
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  • 6
    Electronic Resource
    Electronic Resource
    Poloidal asymmetry and gradient drive in core electron density and temperature fluctuations on the Texas Experimental Tokamak-Upgrade (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2013-2021 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron temperature and density fluctuations are measured in the core of the Texas Experimental Tokamak-Upgrade (TEXT-U) [P. H. Edmonds, E. R. Solano, and A. J. Wootton, in Proceedings of the 15th Symposium on Fusion Technology, Utrecht (Elsevier Science, Amsterdam, 1989), Vol. 1, p. 342] plasma across the poloidal cross section. The high spatial resolution of the heavy-ion beam probe (HIBP) and correlation radiometry of electron cyclotron emission (CRECE) reveal that both the density and temperature fluctuations are strongly poloidally asymmetric. Temperature fluctuation measurements indicate a broadband drift wave feature localized near the plasma equatorial plane on both the high- and low-field sides, which is consistent with density fluctuation measurements by far infrared (FIR) scattering. In contrast, the HIBP observes this feature localized only to the low-field side. Excellent spatial resolution allows us to investigate whether changes in the gradient affect the fluctuation amplitudes. We find that indeed, the temperature fluctuations increase with the electron temperature gradient. Results also link density fluctuations to changes in the density gradient. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871998
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Experimental studies of plasma transport across a magnetic island in the Compact Auburn Torsatron (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 2405-2409 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A set of experiments on the Compact Auburn Torsatron [Gandy et al., Fusion Technol. 18, 281 (1990)] has investigated plasma particle transport properties across a magnetic island. The size of the island was systematically varied and the resulting changes in plasma transport were determined. Measurements of plasma density, electron and ion temperature, and plasma rotation speed were performed. Using a simple diffusion model, these measurements were used to deduce the diffusion coefficients for ions and electrons. With a factor of 2 increase in island width, the ion diffusion coefficient remained nearly constant whereas the electron diffusion coefficient increased by a factor of 4. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872916
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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Effects of applied rotating magnetic perturbations on ion drift orbits in the Compact Auburn Torsatron (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 162-168 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion drift surfaces in the presence of applied rotating magnetic perturbations in the Compact Auburn Torsatron (CAT) [Fusion Technol. 18, 281 (1990)] have been studied. A compact, monoenergetic ion gun was used to launch a continuous beam of 6Li+ ions in the vacuum magnetic fields of the CAT. The ions are detected on a paddle probe that is swept though a poloidal cross section of the torsatron. The applied magnetic perturbation was produced using helical magnetic perturbation coils capable of generating rotating magnetic islands. Using a fixed energy ion beam the effects of constant frequency perturbations on ion drift orbits were studied as a function of the direction of rotation, amplitude, and frequency of the perturbation. A drift Hamiltonian model was developed to simulate ion trajectories in the presence of constant frequency rotating islands. The results of this experiment agree well with the predictions of the Hamiltonian model. Preliminary results of ion orbit modification by swept-frequency, rotating magnetic perturbations are also presented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872127
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