Fiber optic two-color vibration compensated interferometer for plasma density measurements

Zeeland, M. A. Van; Boivin, R. L.; Carlstrom, T. N.; Deterly, T.M.; Finkenthal, D. K.

doi:10.1063/1.2336437

Cited by 56 publications

(31 citation statements)

References 5 publications

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“…On-axis beam injection during the current ramp drives Alfvén eigenmodes, 88 which must be avoided due to their significant transport effect on beam ions. A steady electron density [from interferometry, 89 Fig. 1(c)].…”

Section: Experimental Setup a Typical Plasma Parameters And Nbimentioning

confidence: 99%

Energetic ion transport by microturbulence is insignificant in tokamaks

et al. 2013

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Energetic ion transport due to microturbulence is investigated in magnetohydrodynamic-quiescent plasmas by way of neutral beam injection in the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)]. A range of on-axis and off-axis beam injection scenarios are employed to vary relevant parameters such as the character of the background microturbulence and the value of E b =T e , where E b is the energetic ion energy and T e the electron temperature. In all cases, it is found that any transport enhancement due to microturbulence is too small to observe experimentally. These transport effects are modeled using numerical and analytic expectations that calculate the energetic ion diffusivity due to microturbulence. It is determined that energetic ion transport due to coherent fluctuations (e.g., Alfvén eigenmodes) is a considerably larger effect and should therefore be considered more important for ITER. V C 2013 AIP Publishing LLC.

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Section: Experimental Setup a Typical Plasma Parameters And Nbimentioning

confidence: 99%

Energetic ion transport by microturbulence is insignificant in tokamaks

et al. 2013

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“…The value of the safety factor on axis was generally allowed to decrease below unity as, on the Alcator C-Mod tokamak, sawteeth are generally observed to trigger L-I transitions [14]. The electron temperature was measured by the Thomson Scattering (TS) [20] as well as by the Electron Cyclotron Emission (ECE) diagnostics [21]; density was gauged by TS, CO 2 Interferometer [22] and microwave reflectometry [23]; ion temperature along with toroidal and poloidal velocities were obtained by the Charge Exchange Recombination diagnostic (CER) [24]; fluctuations were monitored by a number of diagnostics including Beam Emission Spectroscopy (BES) [25], Doppler Back Scattering (DBS) [26] along with the Phase Contrast Imaging (PCI) [27,28], whose results are the focus of this paper. The normalized radial coordinate used throughout this paper is defined as the squared root of the normalized toroidal flux.…”

Section: Experimental Set-upmentioning

confidence: 99%

Characterization of density fluctuations during the search for an I-mode regime on the DIII-D tokamak

et al. 2015

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Abstract. The I-mode regime, routinely observed on the Alcator C-Mod tokamak, is characterized by an edge energy transport barrier without an accompanying particle barrier and with broadband instabilities, known as Weakly Coherent Modes (WCM), believed to regulate particle transport at the edge. Recent experiments on the DIII-D tokamak exhibit I-mode characteristics in various physical quantities. These DIII-D plasmas evolve over long periods, lasting several energy confinement times, during which the edge electron temperature slowly evolves towards an H-modelike profile, while maintaining a typical L-mode edge density profile. During these periods, referred to as I-mode phases, the radial electric field at the edge also gradually reaches values typically observed in H-mode. Density fluctuations measured with the Phase Contrast Imaging diagnostic during Imode phases exhibit three features typically observed in H-mode on DIII-D, although they develop progressively with time and without a sharp transition: the intensity of the fluctuations is reduced; the frequency spectrum is broadened and becomes nonmonotonic; two dimensional space-time spectra appear to approach those in H-mode, showing phase velocities of density fluctuations at the edge increasing to about 10 km/s. However, in DIII-D there is no clear evidence of the WCM. Preliminary linear gyro-kinetic simulations are performed in the pedestal region with the GS2 code and its recently upgraded model collision operator that conserves particles, energy and momentum. The increased bootstrap current and flow shear generated by the temperature pedestal are shown to decrease growth rates, thus possibly generating a feedback mechanism that progressively stabilizes fluctuations.

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“…It is followed by the 0-degree antenna beginning at t = 1000.40 ms. During the fast wave heating period there is also neutral beam heating of P NBI = 5 MW. Figure 1(b) contains the time evolution of the core electron temperature (T e (0), from the electron cyclotron emission system [13]), line-averaged electron density (n e , from a CO 2 interferometer [14]) and neutron rate (N, from detectors [15]). At t ≈ 1000 ms there is a significant temperature increase due to a steady 5 MW of neutral beam power and the beginning of fast wave injection.…”

Section: Methodsmentioning

confidence: 99%

Scrape-off layer ion acceleration during fast wave injection in the DIII-D tokamak

Pace¹,

Pinsker²,

Heidbrink³

et al. 2012

Nucl. Fusion

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Fast wave injection is employed on the DIII-D tokamak as a current drive and electron heating method. Bursts of energetic ions with energy E o > 20 keV are observed immediately following fast wave injection in experiments featuring the 8th ion cyclotron harmonic near the antenna. Using the energy and pitch angle of the energetic ion burst as measured by a fast-ion loss detector, it is possible to trace the origin of these ions to a particular antenna. The ion trajectories exist entirely within the scrape-off layer. These observations are consistent with the presence of parametric decay instabilities near the antenna strap. It is suggested that the phase space capabilities of the loss detector diagnostic can improve studies of wave injection coupling and efficiency in tokamaks by directly measuring the effects of parametric decay thresholds.

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Fiber optic two-color vibration compensated interferometer for plasma density measurements

Cited by 56 publications

References 5 publications

Energetic ion transport by microturbulence is insignificant in tokamaks

Energetic ion transport by microturbulence is insignificant in tokamaks

Characterization of density fluctuations during the search for an I-mode regime on the DIII-D tokamak

Scrape-off layer ion acceleration during fast wave injection in the DIII-D tokamak

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