TITLE

Role of trapped electron mode turbulence in internal transport barrier control in the Alcator C-Mod Tokamak

AUTHOR(S)
Ernst, D. R.; Bonoli, P. T.; Catto, P. J.; Doriand, W.; Fiore, C. L.; Granetz, R. S.; Greenwald, M.; Hubbard, A. E.; Porkolab, M.; Redi, M. H.; Rice, J. E.; Zhurovich, K.
PUB. DATE
May 2004
SOURCE
Physics of Plasmas;May2004, Vol. 11 Issue 5, p2637
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Nonlinear gyrokinetic simulations of trapped electron mode (TEM) turbulence, within an internal particle transport barrier, are performed and compared with experimental data. The results provide a mechanism for transport barrier control with on-axis radio frequency heating, as demonstrated in Alcator C-Mod experiments [S. J. Wukitch et al., Phys. Plasmas 9, 2149 (2002)]. Off-axis heating produces an internal particle and energy transport barrier after the transition to enhanced D ahigh confinement mode. The barrier foot reaches the half-radius, with a peak density 2.5 times the edge density. While the density profile peaks, the temperature profile remains relatively unaffected. The peaking and concomitant impurity accumulation are controlled by applying modest central heating power late in the discharge. Gyrokinetic turbulence simulations of the barrier formation phase, using the GS2 code [W. Dorland et al., Phys. Rev. Lett. 85, 5579 (2000)] show that toroidal ion temperature gradient driven modes are suppressed inside the barrier foot, but continue to dominate in the outer half-radius. As the density gradient steepens further, trapped electron modes are driven unstable. The onset of TEM turbulence produces an outflow that strongly increases with the density gradient, upon exceeding a new nonlinear critical density gradient, which significantly exceeds the linear critical density gradient. The TEM turbulent outflow ultimately balances the inward Ware pinch, leading to steady state. Moreover, the simulated turbulent particle diffusivity matches that inferred from particle balance using measured density profile data and the calculated Ware pinch. This turbulent diffusivity exhibits a strong unfavorable temperature dependence that allows control with central heating.
ACCESSION #
12952611

 

Related Articles

  • Turbulence Induced Transport in Tokamaks. Caldas, I. L.; Marcus, F. A.; Batista, A. M.; Viana, R. L.; Lopes, S. R.; Heller, M. V. A. P.; Guimarães-Filho, Z. O.; Morrison, P. J.; Horton, W. // AIP Conference Proceedings;2006, Vol. 875 Issue 1, p341 

    This report is concerned with plasma edge turbulence and its relation to anomalous particle transport in tokamaks. First, experimental evidence of turbulence driven particle transport and measurements of the gradients of the equilibrium profiles in the Brazilian tokamaks TBR and TCABR are...

  • Edge and scrape-off layer tokamak plasma turbulence simulation using two-field fluid model. Bisai, Nirmal; Das, Amita; Deshpande, Shishir; Jha, Ratneshwar; Kaw, Predhiman; Sen, Abhijit; Singh, Raghvendra // Physics of Plasmas;Jul2005, Vol. 12 Issue 7, p072520 

    A novel two-dimensional (2D) fluid model is proposed for investigating flux-driven plasma turbulence in the tokamak edge and scrape-off layer (SOL). Unlike most previous turbulence simulations of this region, the 2D model treats the two regions in a consolidated manner with a smooth transition...

  • The existence of normal equilibrium in tokamaks with negative current in the column center. Pozdnyakov, Yu. I. // Physics of Plasmas;Aug2005, Vol. 12 Issue 8, p084503 

    Plasma rotation is shown to remove the impossibility of the existence of “normal” equilibrium in a tokamak with reversed current. The mathematical procedure of how to overcome the peculiarities, which appear in the equilibrium equations due to current reversal, is suggested. An...

  • Saturation levels of neoclassical tearing modes in International Thermonuclear Experimental Reactor plasmas. Lütjens, Hinrich; Luciani, Jean-François // Physics of Plasmas;Aug2005, Vol. 12 Issue 8, p080703 

    For the future ITER tokamak (International Thermonuclear Experimental Reactor) plasmas [R. Aymar et al., Nucl. Fusion 41, 1301 (2001)] a simple and robust theoretical model for the prediction of the dynamics of neoclassical tearing modes (NTM) is a crucial topic. Presently, this theory is...

  • Fast growing double tearing modes in a tokamak plasma. Bierwage, Andreas; Benkadda, Sadruddin; Hamaguchi, Satoshi; Wakatani, Masahiro // Physics of Plasmas;Aug2005, Vol. 12 Issue 8, p082504 

    Configurations with nearby multiple resonant surfaces have broad spectra of linearly unstable coupled tearing modes with dominant high poloidal mode numbers m. This was recently shown for the case of multiple q=1 resonances [Bierwage et al., Phys. Rev. Lett. 94 65001 (2005)]. In the present...

  • Nonaxisymmetric shaping of tokamaks preserving quasiaxisymmetry. Long-Poe Ku; Boozer, Allen H. // Physics of Plasmas;Aug2009, Vol. 16 Issue 8, p082506 

    If quasiaxisymmetry is preserved, nonaxisymmetric shaping can be used to design tokamaks that do not require current drive, are resilient to disruptions, and have robust plasma stability without feedback. Suggestions for addressing the critical issues of tokamaks can only be validated when...

  • Investigation on the Characteristics of Pellet Ablation in a Toroidal Plasma. Sato, K. N.; Sakakita, H.; Fujita, H. // AIP Conference Proceedings;2003, Vol. 669 Issue 1, p52 

    Characteristics of a cloud ablated from an ice pellet has been investigated in detail in the JIPP T-IIU tokamak plasma by utilizing a new scheme of pellet injection system, "the injection-angle controllable system". A long "helical tail" of ablation light has been observed using CCD cameras and...

  • Monitoring of the Plasma Isotope Composition by Charge-Exchange Neutral Fluxes in a Rippled Toroidal Magnetic Field. Khudoleev, A. V.; Farhbach, H.-U. // Plasma Physics Reports;Feb2004, Vol. 30 Issue 2, p178 

    To determine the hydrogen isotope ratio in plasma from charge-exchange neutral fluxes, certain assumptions are traditionally adopted, the most restrictive of which concerns the form of the ion distribution function, which is usually assumed to be Maxwellian. For large tokamaks, however,...

  • Self-Organization of Plasma in Tokamaks. Dnestrovskij, Yu. N.; Dnestrovskij, A. Yu.; Lysenko, S. E. // Plasma Physics Reports;Jul2005, Vol. 31 Issue 7, p529 

    A review is given of the main ideas regarding self-organization of a tokamak plasma. The analysis begins with a simple model of canonical profiles that was proposed by Kadomtsev for a plasma column with a circular cross section. Kadomtsev�s model is then generalized to a tokamak plasma with...

Share

Read the Article

Courtesy of THE LIBRARY OF VIRGINIA

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

Try another library?
Sign out of this library

Other Topics