Turbulence measurements in fusion plasmas

Turbulence measurements in magnetically confined toroidal plasmas have a long history and relevance due to the detrimental role of turbulence induced transport on particle, energy, impurity and momentum confinement. The turbulence—the microscopic random fluctuations in particle density, temperature, potential and magnetic field—is generally driven by radial gradients in the plasma density and temperature. The correlation between the turbulence properties and global confinement, via enhanced diffusion, convection and direct conduction, is now well documented. Theory, together with recent measurements, also indicates that non-linear interactions within the turbulence generate large scale zonal flows and geodesic oscillations, which can feed back onto the turbulence and equilibrium profiles creating a complex interdependence. An overview of the current status and understanding of plasma turbulence measurements in the closed flux surface region of magnetic confinement fusion devices is presented, highlighting some recent developments and outstanding problems.

[1]  P. Diamond,et al.  Physics of zonal flows , 2005 .

[2]  X. Garbet,et al.  Kinetic theory of electromagnetic geodesic acoustic modes , 2008 .

[3]  Flux surface shaping effects on tokamak edge turbulence and flows , 2005, physics/0509182.

[4]  K. H. Burrell,et al.  Effects of E×B velocity shear and magnetic shear on turbulence and transport in magnetic confinement devices , 1997 .

[5]  P. T. Bonoli,et al.  Role of trapped electron mode turbulence in internal transport barrier control in the Alcator C-Mod Tokamak , 2004 .

[6]  Jose Milovich,et al.  Toroidal gyro‐Landau fluid model turbulence simulations in a nonlinear ballooning mode representation with radial modes , 1994 .

[7]  G. Staebler,et al.  Comparing simulation of plasma turbulence with experiment , 2002 .

[8]  Turbulence behaviour during electron heated reversed shear discharges in JET , 2002 .

[9]  L. G. Eliseev,et al.  Experimental progress on zonal flow physics in toroidal plasmas , 2007 .

[10]  Wootton,et al.  Evidence for confinement improvement by velocity-shear suppression of edge turbulence. , 1990, Physical review letters.

[11]  S. Zweben,et al.  Edge turbulence measurements in toroidal fusion devices , 2007 .

[12]  K. Kawahata,et al.  Impact of nonlocal electron heat transport on the high temperature plasmas of LHD , 2006 .

[13]  John M. Dawson,et al.  Geodesic Acoustic Waves in Hydromagnetic Systems , 1968 .

[14]  Scott.  Self-sustained collisional drift-wave turbulence in a sheared magnetic field. , 1990, Physical review letters.

[15]  E. Joffrin,et al.  Magnetic shear effects on confinement and electron heat transport in Tore Supra discharges with electron heating , 1998 .

[16]  H. R. Wilson,et al.  REVIEW ARTICLE: A review of theories of the L-H transition , 2000 .

[17]  Y. Hamada,et al.  Observation of the fast potential change at L-H transition by a heavy-ion-beam probe on JFT-2M. , 2002, Physical review letters.

[18]  J. Kinsey,et al.  Broad wavenumber turbulence and transport during Ohmic and electron cyclotron heating in the DIII-D tokamak , 2007 .

[19]  G. Tynan,et al.  Scaling of plasma turbulence suppression with velocity shear , 2002 .

[20]  T. S. Hahm,et al.  Zonal flows in plasma—a review , 2005 .

[21]  E. Synakowski,et al.  Core poloidal rotation and internal transport barrier formation in TFTR , 1998 .

[22]  P. Gohil,et al.  Structure and scaling properties of the geodesic acoustic mode , 2006 .

[23]  M. Diesso,et al.  Instrumental aspects of extraordinary mode scattering on TFTR , 1990 .

[24]  J. Weiland,et al.  Collisionality and shear dependences of density peaking in JET and extrapolation to ITER , 2005 .

[25]  B. Leblanc,et al.  High-speed imaging of edge turbulence in NSTX , 2004 .

[26]  E. Doyle,et al.  Physics of the L-mode to H-mode transition in tokamaks , 1992 .

[27]  A. Ejiri,et al.  Bispectral analysis applied to coherent floating potential fluctuations obtained in the edge plasmas on JFT-2M , 2006 .

[28]  J. Weiland,et al.  Physics of transport in tokamaks , 2004 .

[29]  P. Liewer.  Measurements of microturbulence in tokamaks and comparisons with theories of turbulence and anomalous transport , 1985 .

[30]  B. Kurzan,et al.  Measurement and scaling of the radial correlation lengths of turbulence at the plasma edge of ASDEX Upgrade , 2000 .

[31]  R. Fonck,et al.  Detection of zero-mean-frequency zonal flows in the core of a high-temperature tokamak plasma. , 2006, Physical review letters.

[32]  P. Hennequin.  Scaling laws of density fluctuations in tokamak plasmas , 2006 .

[33]  X. Garbet,et al.  Turbulence in fusion plasmas: key issues and impact on transport modelling , 2001 .

[34]  J. Rice,et al.  Observations of Anomalous Momentum Transport in Alcator C-Mod Plasmas with No Momentum Input , 2004 .

[35]  P. M. Ryan,et al.  Overview of recent physics results from the National Spherical Torus Experiment (NSTX) , 2007 .

[36]  Measurements of ion temperature fluctuations in the Tokamak Fusion Test Reactor , 1998 .

[37]  H. Zohm,et al.  Radial correlation length measurements on ASDEX Upgrade using correlation Doppler reflectometry , 2007 .

[38]  R. Bickerton.  REVIEW ARTICLE: Magnetic turbulence and the transport of energy and particles in tokamaks , 1997 .

[39]  A. Kendl.  Linear aspects of streamer formation in electron temperature gradient turbulence , 2003 .

[40]  U. Stroth,et al.  Transport in toroidal devices-the experimentalist's view , 1992 .

[41]  Coupling of turbulence and reflectometer simulation codes and comparison with experiment , 2002 .

[42]  K. Burrell.  Turbulence behaviour in the presence of transport barriers , 2006 .

[43]  P. Diamond,et al.  Experimental studies of zonal flow and field in compact helical system plasma , 2008 .

[44]  E. Doyle,et al.  Characterization of avalanche-like events in a confined plasma , 2001 .

[45]  Paul,et al.  Long-wavelength density turbulence in the TFTR tokamak. , 1993, Physical review letters.

[46]  K. Narihara,et al.  Streamers in the JIPP T-llU tokamak plasmas. , 2006, Physical review letters.

[47]  X. Garbet,et al.  Recent results on turbulence and MHD activity achieved by reflectometry , 2006 .

[48]  B. Carreras.  Plasma edge cross-field transport: experiment and theory , 2005 .

[49]  B. Scott,et al.  Direct measurement of zonal flows and geodesic acoustic mode oscillations in ASDEX Upgrade using Doppler reflectometry , 2005 .

[50]  L. Colas,et al.  Internal magnetic fluctuations and electron heat transport in the Tore Supra tokamak: Observation by cross-polarization scattering , 1998 .

[51]  H R Wilson,et al.  Survey of theories of anomalous transport , 1994 .

[52]  J. Y. Chen,et al.  Comparison of the density fluctuation spectrum and amplitude in TEXT with expectations for electron drift waves , 1992 .

[53]  R. Kraichnan.  Inertial Ranges in Two‐Dimensional Turbulence , 1967 .

[54]  W. Horton.  Drift waves and transport , 1999 .

[55]  F. Jenko,et al.  Relationship between density peaking, particle thermodiffusion, Ohmic confinement, and microinstabilities in ASDEX Upgrade L-mode plasmas , 2005 .

[56]  N. Bretz.  Diagnostic instrumentation for microturbulence in tokamaks , 1997 .

[57]  G. Staebler,et al.  Search for the ion temperature gradient mode in a tokamak plasma and comparison with theoretical predictions , 2001 .

[58]  E. Doyle,et al.  Response of multiscale turbulence to electron cyclotron heating in the DIII-D tokamaka) , 2007 .

[59]  A. Wootton,et al.  Fluctuations and anomalous transport in tokamaks , 1990 .

[60]  Frank Jenko,et al.  Electron temperature gradient driven turbulence , 1999 .

[61]  R. Fonck,et al.  Plasma Turbulence Imaging via Beam Emission Spectroscopy in the Core of the DIII-D Tokamak , 2007 .

[62]  F. Hinton,et al.  Theory of plasma transport in toroidal confinement systems , 1976 .

[63]  Paul,et al.  Observation of a localized transition from edge to core density turbulence in the TFTR tokamak. , 1993, Physical review letters.

[64]  T. L. Rhodes,et al.  Measurements of core electron temperature and density fluctuations in DIII-D and comparison to nonlinear gyrokinetic simulations , 2008 .

[65]  X. Garbet,et al.  Scaling laws of density fluctuations at high-k on Tore Supra , 2004 .

[66]  J. Hugill.  REVIEW ARTICLE: Edge turbulence in tokamaks and the L-mode to H-mode transition , 2000 .

[67]  John Sheffield,et al.  The physics of magnetic fusion reactors , 1994 .

[68]  P. Terry,et al.  Suppression of turbulence and transport by sheared flow , 2000 .

[69]  Y. Hamada,et al.  Geodesic–acoustic-mode in JFT-2M tokamak plasmas , 2006 .

[70]  C. Hidalgo.  Edge turbulence and anomalous transport in fusion plasmas , 1995 .

[71]  G. Conway,et al.  Frequency scaling and localization of geodesic acoustic modes in ASDEX Upgrade , 2008 .

[72]  F. Jenko,et al.  Scale separation between electron and ion thermal transport. , 2008, Physical review letters.

[73]  K. Kawahata,et al.  Effect of Magnetic Configuration on Particle Transport and Density Fluctuation in LHD , 2007 .

[74]  E. Doyle,et al.  Comparison of turbulence measurements from DIII-D low-mode and high-performance plasmas to turbulence simulations and models , 2001 .

[75]  A. Sips,et al.  Turbulence reduction in internal transport barriers on ASDEX Upgrade , 2001 .

[76]  J. Connor.  Tokamak turbulence-electrostatic or magnetic? , 1993 .

[77]  W. Dorland,et al.  Microstability physics as illuminated in the spherical tokamak , 2005 .

[78]  G. Conway.  Amplitude behaviour of geodesic acoustic modes in the ASDEX Upgrade tokamak , 2008 .

[79]  F. Ryter,et al.  Observations on core turbulence transitions in ASDEX Upgrade using Doppler reflectometry , 2006 .

[80]  A. Petrov,et al.  Investigation of small-scale tokamak plasma turbulence by correlative UHR backscattering diagnostics , 2006 .

[81]  P. Gohil,et al.  Dynamics of the formation, sustainment and destruction of transport barriers in magnetically contained fusion plasmas* , 2002 .

[82]  T. Lan,et al.  Spectral characteristics of geodesic acoustic mode in the HL-2A tokamak , 2008 .

[83]  J. Kinsey,et al.  Non-dimensional scaling of turbulence characteristics and turbulent diffusivity , 2001 .

[84]  S. E. Lysenko,et al.  Investigation of geodesic acoustic mode oscillations in the T-10 tokamak , 2006 .

[85]  Kim,et al.  Observation of a high-density ion mode in tokamak microturbulence. , 1987, Physical review letters.

[86]  A. Melnikov,et al.  Summary of experimental core turbulence characteristics in ohmic and electron cyclotron resonance heated discharges in T-10 tokamak plasmas , 2005 .

[87]  F. Leuterer,et al.  Experimental study of trapped-electron-mode properties in tokamaks: threshold and stabilization by collisions. , 2005, Physical review letters.

[88]  W. Suttrop,et al.  Plasma rotation profile measurements using Doppler reflectometry , 2004 .