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  • 1985-1989  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Experimental study of millimeter wave radiation from a rotating electron beam in a rippled magnetic field (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 1962-1967 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The generation of millimeter wave radiation from the interaction of a rotating electron beam (2 MeV, 1 kA, 5 nsec) with an azimuthally periodic wiggler magnetic field has been studied experimentally. Calculations of the effects of the wiggler magnetic field on the single particle electron orbits are presented, together with experimental measurements of the effects of the wiggler field on the electron beam. Narrow-band radiation at power levels in excess of 200 kW has been observed at 88 and 175 GHz for wiggler fields with 6.28 and 3.14 cm periods, respectively. The radiation frequency spectra for various experimental configurations are presented, and results are compared with theoretical expectations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.864941
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    q=2 sawteeth and major disruptions in tokamaks (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 475-482 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In numerical simulations of q=2 tearing modes, the maximum amplitude of the mode is found to increase rapidly as the safety factor on axis q(0) rises above 1.5. The associated magnetic islands grow to the center of the column, encompassing virtually the entire plasma cross section. As a result of the formation of these very large islands, the hot central plasma is rapidly convected out to the edge of the column, thereby destroying central confinement. Experimental evidence from several tokamaks linking the formation of these very large islands with major disruptions is presented. Typically, major disruptions are observed to occur in two (or more) stages. During the first stage(s) q rises on axis while the final stage, which terminates the discharge, is associated with the violent growth of an m=2 perturbation. Under some circumstances q=2 sawteeth are predicted to occur. Evidence for such sawteeth in a divertor tokamak is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865433
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Study of optically thin electron cyclotron emission from TFTR using a Michelson interferometer (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1997-1997 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The tokamak fusion test reactor (TFTR) Michelson interferometer, which is used as an electron-temperature diagnostic, has a spectral range of 75–540 GHz. This range is adequate for measuring at least the first three cyclotron harmonics, and it spans both optically thick and thin portions of the electron cyclotron emission (ECE) spectrum. During the most recent opening of the TFTR vacuum vessel, a concave, carbon reflector was installed on the back wall of the vessel, opposite the light-collecting optic of the Michelson system. The reflector is designed to prevent the observation of optically thin ECE that originates from a location that is outside the field of view of the light collecting optic. If this is achieved, it should be possible to derive the electron-density profile from measurements of either the extraordinary mode third harmonic or the ordinary mode second harmonic. An analysis of ECE spectra that have been measured before and after installation of the reflector will be presented. This work was supported by U.S. DOE Contract No. DE-AC02-76-CHO-3073.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138765
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    New diagnostic for spheromaks? What are the possibilities? (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1962-1964 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Electron cyclotron emission from a spheromak plasma may be able to provide information about the confining magnetic field. Emission generated in the extraordinary mode with its electric vector perpendicular to the local magnetic field at sufficiently high frequency will propagate out of the plasma while retaining the orientation of the electric vector that it had at its source. Thus a measurement of the orientation of the emergent electric vector and the frequency of the emitted wave will allow one to deduce the orientation and strength of the magnetic field at the radiation source. A simple model of the Maryland spheromak is used to determine the practicality of this diagnostic possibility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138807
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    ECE diagnostic for the TARA tandem mirror machine using a fast-scanning Michelson interferometer (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1965-1967 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This ECE (electron cyclotron emission) diagnostic utilizes a fast-scanning Michelson interferometer to determine two parameters, the temperature and the loss cone angle, of the distribution function of the hot electrons (T(approximately-greater-than)100 keV) generated in the axisymmetric plug plasma of the TARA tandem mirror device. The radiation transport system employs a lens relay and a low-pass grating filter in order to transmit the synchrotron radiation over a spectral range of 2.9–18.6 cm−1. This enables us to study the emitted radiation spectrum up to the 40th harmonic of the electron–cyclotron frequency in the plug plasma (B=5 kG). Details of the design principles and the development of the diagnostic at TARA will be presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138808
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    TFTR Michelson interferometer electron cyclotron emission diagnostic (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 925-927 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In July 1984, a Fourier transform spectrometer employing a fast-scanning Michelson interferometer began operating on TFTR. This diagnostic system can measure the electron cyclotron emission spectrum 72 times per s with a time resolution of 11 ms and a spectral resolution of 3.6 GHz. The initial operating spectral range is 75–540 GHz, which is adequate for measuring the first three cyclotron harmonics at present TFTR magnetic field levels. The range can be extended easily to 75–1080 GHz in order to accommodate increases in toroidal magnetic field or to study superthermal ECE. The measured spectra are absolutely calibrated using a liquid nitrogen cooled blackbody reference source. The second harmonic feature of each spectrum is used to calculate the absolute electron temperature profile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138044
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Broadband measurement of electron cyclotron emission in TFTR using a quasioptical light collection system and a polarizing Michelson interferometer (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 2139-2148 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For the past four years, a Fourier transform spectrometer diagnostic system, employing a fast-scanning polarizing Michelson interferometer (FMI), has been operating on the TFTR tokamak at the Princeton Plasma Physics Laboratory. It is used to measure the electron cyclotron emission (ECE) spectrum over the range 2.5–18 cm−1 (75–540 GHz), with a resolution of 0.123 cm−1 (3.7 GHz), at a rate of 72 spectra per second. The quasioptical system for collecting the light and transporting it through the interferometer to the detector has been designed using the concepts of both Gaussian and geometrical optics. The commercial FMI was custom made for this project and is the state of the art for this type of specialized instrument. The diagnostic system is described and an error propagation analysis of the absolute calibration process is given. Examples of ECE spectra measured in two polarization directions are given and electron temperature profiles derived from each of them are compared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139976
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Reflectance characteristics in the submillimeter and millimeter wavelength region of a vacuum compatible absorber (1987)
    Springer
    International journal of infrared and millimeter waves 8 (1987), S. 627-635 
    Details
    ISSN: 1572-9559
    Keywords: reflectance ; Macor ; submillimeter and millimeter waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The reflectance characteristics of a grooved sample of Corning Macor, a glass ceramic, were studied in the range 60–1100 GHz for incident and reflected angles ranging from 10° to 65°. Measurements indicate a low, 〈1%, reflectance for near normal angles of incidence, where the angles of incidence and reflection are defined with respect to a direction normal to the sample face as if it were a planar surface. Higher values, up to 6%, were obtained for other angles of incidence and these results depend upon the orientation of the sample grooves with respect to the polarization of the electric field of the incoming radiation. Structure in the spectra indicates complex interference effects in some configurations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01010634
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    Paper (German National Licenses)
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