Measurements of the cross-phase angle between density and electron temperature fluctuations and comparison with gyrokinetic simulations

White, A. E.; Peebles, W. A.; Rhodes, T. L.; Holland, C. H.; Wang, G.; Schmitz, L.; Carter, T. A.; Hillesheim, J. C.; Doyle, E. J.; Zeng, L.; McKee, G. R.; Staebler, G. M.; Waltz, R. E.; DeBoo, J. C.; Petty, C. C.; Burrell, K. H.
May 2010
Physics of Plasmas;May2010, Vol. 17 Issue 5, p056103
Academic Journal
This paper presents new measurements of the cross-phase angle, αneTe, between long-wavelength (kθρs<0.5) density, ñe, and electron temperature, Te, fluctuations in the core of DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] tokamak plasmas. The coherency and cross-phase angle between ñe and Te are measured using coupled reflectometer and correlation electron cyclotron emission diagnostics that view the same plasma volume. In addition to the experimental results, two sets of local, nonlinear gyrokinetic turbulence simulations that are performed with the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] are described. One set, called the pre-experiment simulations, was performed prior to the experiment in order to predict a change in αneTe given experimentally realizable increases in the electron temperature, Te. In the experiment the cross-phase angle was measured at three radial locations (ρ=0.55, 0.65, and 0.75) in both a “Base” case and a “High Te” case. The measured cross-phase angle is in good qualitative agreement with the pre-experiment simulations, which predicted that ñe and Te would be out of phase. The pre-experiment simulations also predicted a decrease in cross-phase angle as Te is increased. Experimentally, this trend is observed at the inner two radial locations only. The second set of simulations, the postexperiment simulations, is carried out using local parameters taken from measured experimental profiles as input to GYRO. These postexperiment simulation results are in good quantitative agreement with the measured cross-phase angle, despite disagreements with transport fluxes. Directions for future modeling and experimental work are discussed.


Related Articles

  • Estimates of the local parameters of plasma density fluctuations by reflectometry measurements. Shelukhin, D.; Soldatov, S.; Vershkov, V.; Urazbaev, A. // Plasma Physics Reports;Sep2006, Vol. 32 Issue 9, p707 

    The question is considered of how to estimate the parameters of local plasma density fluctuations from reflectometry measurements made by probing the plasma with an extraordinary electromagnetic wave. In the geometrical-optics approximation, a formula is derived that relates the fluctuation...

  • Towards the Detection of Magnetohydrodynamics Instabilities in a Fusion Reactor. Sozzi, C.; Alessi, E.; Figini, L.; Galperti, G.; Lazzaro, E.; Marchetto, C.; Mosconi, M.; Nowak, S. // AIP Conference Proceedings;2014, Vol. 1612, p35 

    Various active control strategies of the Neoclassical tearing modes are being studied in present tokamaks using established detection techniques which exploit the measurements of the fluctuations of the magnetic field and of the electron temperature. The extrapolation of such techniques to the...

  • Investigation of mechanisms for He-I emission radial profile broadening in a weakly ionized cylindrical helium plasma with recombining edge. Hollmann, E. M.; Brandt, C.; Hudson, B.; Kumar, D.; Nishijima, D.; Pigarov, A. Yu. // Physics of Plasmas;Sep2013, Vol. 20 Issue 9, p093303 

    Spatially resolved spectroscopic measurements of He-I line emission are used to study the causes of emission profile broadening radially across the cylinder of a weakly ionized helium plasma. The plasma consists of an ionizing core (r < 2 cm) surrounded by a recombining edge (r > 2 cm) plasma....

  • Ion-temperature-gradient driven modes in dust-contaminated plasma with nonthermal electron distribution and dust charge fluctuations. Zakir, U.; Haque, Q.; Qamar, A.; Mirza, Arshad // Astrophysics & Space Science;Apr2014, Vol. 350 Issue 2, p565 

    The effect of nonthermal electrons on ion-temperature-gradient (ITG) driven modes is investigated in the presence of variable dust charge and ion shear flow. The dust charge fluctuating expression is obtained in the presence of kappa distributed electrons. A dispersion relation is derived and...

  • Thomson-scattering measurements in the collective and noncollective regimes in laser produced plasmas (invited). Ross, J. S.; Glenzer, S. H.; Palastro, J. P.; Pollock, B. B.; Price, D.; Tynan, G. R.; Froula, D. H. // Review of Scientific Instruments;Oct2010, Vol. 81 Issue 10, p10D523 

    We present simultaneous Thomson-scattering measurements of light scattered from ion-acoustic and electron-plasma fluctuations in a N2 gas jet plasma. By varying the plasma density from 1.5×1018 to 4.0×1019 cm-3 and the temperature from 100 to 600 eV, we observe the transition from the...

  • Heterodyne O-mode reflectometer on the JT-60U tokamak. Oyama, N.; Shinohara, K. // Review of Scientific Instruments;Mar2002, Vol. 73 Issue 3, p1169 

    A three-channel heterodyne O-mode reflectometer system has been developed for density fluctuation measurements on the JT-60U tokamak. The system consists of one fixed channel with a frequency of 34 GHz and two selectable frequency channels with frequencies in the range of 34–40 and...

  • Broadband heterodyne reflectometry on the W7-AS stellarator (abstract). Hartfuss, H. J.; Sánchez, J.; Estrada, T. // Review of Scientific Instruments;Oct92, Vol. 63 Issue 10, p4653 

    A broadband heterodyne reflectometer, operating in the frequency range 75-110 GHz, has been installed and operated at the W7-AS Stellarator in Garching for the study of density fluctuations and fast density profile determination. Both local (LO) and signal (rf) oscillators can be swept over the...

  • Numerical study of microwave reflectometry in plasmas with two-dimensional turbulent fluctuations Mazzucato, E. // Review of Scientific Instruments;Apr98, Vol. 69 Issue 4, p1691 

    Describes the role of two-dimensional turbulent fluctuations in microwave reflectometry. Use of reflectometry for measuring plasma density; Description of the technique; Validity of the model; Effect of turbulent fluctuations on the average electron density profile.

  • Theory of weak ion temperature gradient-driven turbulence near the threshold of instability. Mattor, N.; Diamond, P. H. // Physics of Fluids B: Plasma Physics;Oct89, Vol. 1 Issue 10, p1980 

    In this paper a theory of weak ion temperature gradient-driven turbulence near the threshold of instability is presented. The model considers kinetic ions and adiabatic electrons in a sheared slab geometry. Linear theory shows that for ηth<ηi<=ηth+(1+Ti/Te) Ln/Ls (where ηth=0.95 is...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics