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  • 1
    Electronic Resource
    Electronic Resource
    Measurements of electron parallel momentum distributions using cyclotron wave transmission (abstract) : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4618-4618 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The method of cyclotron wave transmission for measuring the electron parallel momentum distribution is studied in a lower-hybrid driven tokamak plasma. Questions of resolution, sensitivity, and technique are addressed. Measurements are made of the suprathermal distribution produced by current drive as well as the incremental changes in the distribution function produced by short pulses of lower-hybrid waves. The results indicate that cyclotron wave transmission is well suited for studies of electron velocity space phenomena and may be used to detect the effect of diagnostic perturbations. This research was supported by the U. S. Department of Energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143688
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  • 2
    Electronic Resource
    Electronic Resource
    A system to measure suprathermal electron distribution functions in toroidal plasmas by electron cyclotron wave absorption : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 496-499 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A two-chord, four-beam suprathermal electron diagnostic has been installed on TdeV (B〉1.5 T, R=0.86 m, a=0.25 m). Resonant absorption of extraordinary mode electron cyclotron waves is measured to deduce the chordal averaged suprathermal electron distribution function amplitude at the resonant momentum. Simultaneously counterpropagating beams permit good refractive loss cancellation. A nonlinear frequency sweep leads to a concentration of appropriately propagating power in a narrow range of time of flight, thus increasing the signal-to-noise ratio and facilitating the rejection of spurious reflections. Numerous measurements of electron distribution functions have been obtained during lower-hybrid current-drive experiments. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147615
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  • 3
    Electronic Resource
    Electronic Resource
    Observation and analysis of a two-parallel-temperature electron tail during lower-hybrid current-drive on a tokamak (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3622-3626 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A "two-parallel-temperature'' feature of the fast-electron distribution function has been observed during lower-hybrid current-drive experiments on the Versator-II tokamak (B. Richards, Ph.D. thesis, Massachusetts Institute of Technology, 1981). Computational modeling predicts this feature and indicates that the colder tail is initiated by low-power, high-N(parallel) waves from the sidelobes of the antenna N(parallel) spectrum. The modeling indicates these waves bridge the "spectral gap,'' enabling current drive even though the wave parallel phase velocity greatly exceeds the electron thermal velocity for the majority of the wave power.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860834
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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Measurements of electron parallel-momentum distributions using cyclotron wave transmissionf| (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 2445-2450 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Practical aspects of the implementation of cyclotron wave transmission diagnostics are considered in three specific areas. Questions raised by the calculation of the diagnostic resolution and sensitivity, elimination of reflections through swept frequency and phase-coherent detection, and correcting for the effects of wave refraction through the use of equivalent rays are addressed. Results of preliminary tests and experiments as well as comments on future implementations are used to illustrate the discussion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860729
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  • 8
    Electronic Resource
    Electronic Resource
    Test particle diagnostics for high-temperature plasmas (abstract) : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3146-3146 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new type of tagging diagnostic which employs ballistic modes to follow particle orbits is introduced. "Vlasov tagging'' is accomplished by the selective excitation of small amplitude ballistic modes either by the resonant Landau or cyclotron resonant absorption of incident waves or by spatially localized nonresonant nonlinear interactions. Subsequent detection of ballistic modes may be accomplished by laser fluorescence (for ions) or by changes in the transmission of a probe beam. Results demonstrating ion Vlasov tagging will be presented. Electron Vlasov tagging appears most attractive by means of the cyclotron resonance. Transmission measurements with a search beam may be made at the harmonics. Vlasov tagging may be used to directly measure transport in both velocity and coordinate space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141661
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  • 9
    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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  • 10
    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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