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  • 11
    Electronic Resource
    Electronic Resource
    Ion cyclotron range of frequency experiments in the Tokamak Fusion Test Reactor with fast waves and mode converted ion Bernstein waves (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2006-2012 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent experiments in the ion cyclotron range of frequencies (ICRF) in the Tokamak Fusion Test Reactor [Fusion Technol. 21, 13 (1992)] are discussed. These experiments include mode conversion heating and current drive, fast wave current drive, and heating of low (L)- mode deuterium–tritium (D–T) plasmas in both the hydrogen minority and second harmonic tritium regimes. In mode conversion heating, a central electron temperature of 10 keV was attained with 3.3 MW of radio-frequency power. In mode conversion current drive experiments, up to 130 kA of current was noninductively driven, on and off axis, and the current profiles were modified. Fast wave current drive experiments have produced 70–80 kA of noninductively driven current. Heating of L-mode deuterium and D–T plasmas by hydrogen minority ICRF has been compared. Finally, heating of L-mode D–T plasmas at the second harmonic of the tritium cyclotron frequency has been demonstrated. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871997
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  • 12
    Electronic Resource
    Electronic Resource
    Ion cyclotron range of frequencies heating and current drive in deuterium–tritium plasmas (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2427-2434 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The first experiments utilizing high-power radio waves in the ion cyclotron range of frequencies to heat deuterium–tritium (D–T) plasmas have been completed on the Tokamak Fusion Test Reactor [Fusion Technol. 21, 13 (1992)]. Results from the initial series of experiments have demonstrated efficient core second harmonic tritium (2ΩT) heating in parameter regimes approaching those anticipated for the International Thermonuclear Experimental Reactor [D. E. Post, Plasma Physics and Controlled Nuclear Fusion Research, Proceedings of the 13th International Conference, Washington, DC, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 3, p. 239]. Observations are consistent with modeling predictions for these plasmas. Efficient electron heating via mode conversion of fast waves to ion Bernstein waves has been observed in D–T, deuterium-deuterium (D–D), and deuterium–helium-4 (D–4He) plasmas with high concentrations of minority helium-3 (3He) (n3He/ne(approximately-greater-than)10%). Mode conversion current drive in D–T plasmas was simulated with experiments conducted in D–3He–4He plasmas. Results show a directed propagation of the mode converted ion Bernstein waves, in correlation with the antenna phasing. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871266
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  • 13
    Electronic Resource
    Electronic Resource
    A mechanism for beam-driven excitation of ion cyclotron harmonic waves in the Tokamak Fusion Test Reactor (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 3407-3413 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A mechanism is proposed for the excitation of waves at harmonics of the injected ion cyclotron frequencies in neutral beam-heated discharges in the Tokamak Fusion Test Reactor (TFTR) [Proceedings of the 17th European Conference on Controlled Fusion and Plasma Heating (European Physical Society, Petit-Lancy, Switzerland, 1990), p. 1540]. Such waves are observed to originate from the outer midplane edge of the plasma. It is shown that ion cyclotron harmonic waves can be destabilized by a low concentration of sub-Alfvénic deuterium or tritium beam ions, provided these ions have a narrow distribution of speeds parallel to the magnetic field. Such a distribution is likely to occur in the edge plasma, close to the point of beam injection. The predicted instability gives rise to wave emission at propagation angles lying almost perpendicular to the field. In contrast to the magnetoacoustic cyclotron instability proposed as an excitation mechanism for fusion-product-driven ion cyclotron emission in the Joint European Torus (JET) [Phys. Plasmas 1, 1918 (1994)], the instability proposed here does not involve resonant fast Alfvén and ion Bernstein waves, and can be driven by sub-Alfvénic energetic ions. It is concluded that the observed emission from TFTR can be driven by beam ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870489
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  • 14
    Electronic Resource
    Electronic Resource
    Transient transport experiments in the current-drive experiment upgrade spherical torus (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 480-487 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron transport has been measured in the Current-Drive Experiment Upgrade (CDX-U) (T. Jones, Ph.D. thesis, Princeton University, 1995) using two separate perturbative techniques. Sawteeth at the q=1 radius (r/a∼0.15) induced outward-propagating heat pulses, providing time-of-flight information leading to a determination of χe as a function of radius. Gas modulation at the plasma edge introduced inward-propagating cold pulses, providing a complementary time-of-flight based χe profile measurement. This work represents the first localized measurement of χe in a spherical torus. Core (r/a〈1/3) χe values from the sawtooth study are 1–2 m2/s, and from the gas modulation study are 1–6 m2/s, increasing by an order of magnitude or more outside of the core region. Furthermore, the χe profile exhibits a sharp transition near r/a=1/3. Spectral and profile analyses of the soft x-rays, scanning interferometer, and edge probe data show no evidence of a significant magnetic island causing the high χe region. Comparisons are performed to several theoretical models, with measured χe(approximate)5–10× neoclassical estimates in the core. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428557
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  • 15
    Electronic Resource
    Electronic Resource
    Measurements on rotating ion cyclotron range of frequencies induced particle fluxes in axisymmetric mirror plasmas (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 2947-2954 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comparison of phenomenological features of plasmas is made with a special emphasis on radio-frequency induced transport, which are maintained when a set of two closely spaced dual half-turn antennas in a central cell of the Phaedrus-B axisymmetric tandem mirror [J. J. Browning et al., Phys. Fluids B 1, 1692 (1989)] is phased to excite electromagnetic fields in the ion cyclotron range of frequencies (ICRF) with m=−1 (rotating with ions) and m=+1 (rotating with electrons) azimuthal modes. Positive and negative electric currents are measured to flow axially to the end walls in the cases of m=−1 and m=+1 excitations, respectively. These parallel nonambipolar ion and electron fluxes are observed to be accompanied by azimuthal ion flows in the same directions as the antenna-excitation modes m. The phenomena are argued in terms of radial particle fluxes due to a nonambipolar transport mechanism [Hojo and Hatori, J. Phys. Soc. Jpn. 60, 2510 (1991); Hatakeyama et al., J. Phys. Soc. Jpn. 60, 2815 (1991), and Phys. Rev. E 52, 6664 (1995)], which are induced when azimuthally traveling ICRF waves are absorbed in the magnetized plasma column. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872427
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  • 16
    Electronic Resource
    Electronic Resource
    Alpha-driven magnetohydrodynamics (MHD) and MHD-induced alpha loss in the Tokamak Fusion Test Reactor : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1610-1616 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Alpha-driven toroidal Alfvén eigenmodes (TAEs) are observed as predicted by theory in the post-neutral beam phase in high central q (safety factor) deuterium–tritium (D–T) plasmas in the Tokamak Fusion Test Reactor (TFTR) [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)]. The mode location, poloidal structure, and the importance of q profile for TAE instability are discussed. So far no alpha particle loss due to these modes was detected due to the small mode amplitude. However, alpha loss induced by kinetic ballooning modes (KBMs) was observed in high-confinement D–T discharges. Particle orbit simulation demonstrates that the wave–particle resonant interaction can explain the observed correlation between the increase in alpha loss and appearance of multiple high-n (n≥6, n is the toroidal mode number) modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872363
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  • 17
    Electronic Resource
    Electronic Resource
    Electron Bernstein wave electron temperature profile diagnostic (invited) : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 285-292 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Electron cyclotron emission (ECE) has been employed as a standard electron temperature profile diagnostic on many tokamaks and stellarators, but most magnetically confined plasma devices cannot take advantage of standard ECE diagnostics to measure temperature. They are either "overdense," operating at high density relative to the magnetic field (e.g., ωpe(very-much-greater-than)Ωce in a spherical torus) or they have insufficient density and temperature to reach the blackbody condition (τ〉2). Electron Bernstein waves (EBWs) are electrostatic waves that can propagate in overdense plasmas and have a high optical thickness at the electron cyclotron resonance layers as a result of their large kperp. In this article we report on measurements of EBW emission on the CDX-U spherical torus, where B0∼2 kG, 〈ne〉∼1013 cm−3 and Te(approximate)10–200 eV. Results are presented for electromagnetic measurements of EBW emission, mode converted near the plasma edge. The EBW emission was absolutely calibrated and compared to the electron temperature profile measured by a multipoint Thomson scattering diagnostic. Depending on the plasma conditions, the mode-converted EBW radiation temperature was found to be ≤Te and the emission source was determined to be radially localized at the electron cyclotron resonance layer. A Langmuir triple probe and a 140 GHz interferometer were employed to measure changes in the edge density profile in the vicinity of the upper hybrid resonance where the mode conversion of the EBWs is expected to occur. Initial results suggest EBW emission and EBW heating are viable concepts for plasmas where ωpe(very-much-greater-than)Ωce. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1308995
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  • 18
    Electronic Resource
    Electronic Resource
    Ion cyclotron emission on the Tokamak Fusion Test Reactor : 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. 817-819 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Preliminary observations of ion cyclotron emission (ICE) have been made in D-T plasmas on the Tokamak Fusion Test Reactor, using an array of seven rf probes located at the top and bottom of the torus. Fusion product line emission has been identified, and appears to originate at the low field equatorial plane, near the radius of the outboard limiter. While the peak intensity of D-T fusion product ICE exhibits a correlation with overall neutron production, the time evolution of the ICE signal does not follow that of the neutron rate. During high power neutral beam injection, beam-species ICE is also observed, with frequencies corresponding to the outer midplane edge of the plasma. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146232
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  • 19
    Electronic Resource
    Electronic Resource
    New electron cyclotron emission diagnostic for measurement of temperature based upon the electron Bernstein wave : 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. 1018-1020 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Most magnetically confined plasma devices cannot take advantage of standard electron cyclotron emission (ECE) diagnostics to measure temperature. They either operate at high density relative to their magnetic field (e.g., ωp(very-much-greater-than)Ωc in spherical tokamaks) or they do not have sufficient density and temperature to reach the blackbody condition (τ〉2). The standard ECE technique measures the electromagnetic waves emanating from the plasma. Here we propose to measure electron Bernstein waves (EBW) to ascertain the local electron temperature in these plasmas. The optical thickness of EBW is extremely high because it is an electrostatic wave with a large ki. For example, the National Spherical Torus Experiment (NSTX) will have an optical thickness τ(approximate)3000 and CDX-U will have τ(approximate)300. One can reach the blackbody condition with a plasma density (approximate)1011 cm−3 and Te(approximate)1 eV. This makes it attractive to most plasma devices. The serious issue with using EBW is the wave accessibility for the emission measurement. Simple accessibility arguments indicate the wave may be accessible by either direct coupling or mode conversion through an extremely narrow layer ((approximate)1–2 mm). EBW experiments on the Current Drive Experiment-Upgrade (CDX-U) will test the accessibility properties of the spherical tokamak configuration. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149464
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  • 20
    Electronic Resource
    Electronic Resource
    Technique for measuring the two-port scattering matrix of a plasma current drive antenna during high power operation (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1168-1175 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a technique to routinely measure the scattering matrix of a radio frequency (rf) current drive antenna in a magnetic fusion experiment during high power operation. This technique can be used under any conditions of phase or amplitude of excitation. It involves modulation of the phase of the rf voltage applied to each of the antenna ports by a few degrees, measurement of the complex forward and reflected voltages, detection of the phase modulation, and solution of a 2×2 matrix problem to yield the scattering matrix. Further calculation then yields the antenna's impedance matrix. Because it involves only a small modulation, this method can be used to routinely monitor matching, decoupling, or plasma loading and to provide input to tuning calculations so that the matching and phasing conditions can be maintained. We show results for the case of 400 kW Alfvèn wave current drive experiments on the Phaedrus-T tokamak. We also show how the results can be used to tune the antenna. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147879
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