Observations of central toroidal rotation in ICRF heated Alcator C-Mod plasmas

Impurity toroidal rotation has been observed in the centre of Alcator C-Mod ion cyclotron range of frequencies (ICRF) heated plasmas, from the Doppler shifts of argon X ray lines. Rotation velocities greater than 1.2 × 107 cm/s (ω = 200 krad/s) in the co-current direction have been observed in H mode discharges that had no direct momentum input. There is a correlation between the increase in the central impurity rotation velocity and the increase in the plasma stored energy (confinement enhancement), induced by ICRF heating, although other factors may be at play. The toroidal rotation velocity is highest near the magnetic axis, and decreases with increasing minor radius. A radial electric field of 300 V/cm at r/a = 0.3 has been inferred from the force balance equation. The direction of the rotation changes when the plasma current direction is reversed, remaining co-current. Impurity toroidal rotation in ICRF heated plasmas is in the direction opposite to the rotation in ohmic L mode plasmas; co-current rotation has also been observed during purely ohmic H modes. When the ICRF heating is turned off, the toroidal rotation decays with a characteristic time of order 50 ms, similar to the energy confinement time, and much shorter than the calculated neoclassical momentum damping time.

[1]  Toroidal plasma rotation in the PLT tokamak with neutral-beam injection , 1981 .

[2]  Elda Righi,et al.  Toroidal rotation in ICRF-heated H-modes on JET , 1997 .

[3]  G. Hammett,et al.  ICH-induced plasma rotation on TFTR , 1996 .

[4]  R. Isler,et al.  Plasma rotation measurements using spectral lines from charge‐transfer reactions , 1983 .

[5]  M. Bell.  Measurements of plasma rotation in tokamak LT-3 , 1979 .

[6]  Experimental determination of non-diffusive toroidal momentum flux in JT-60U , 1994 .

[7]  Tadashi Sekiguchi,et al.  Plasma Physics and Controlled Nuclear Fusion Research , 1987 .

[8]  H. Sanuki,et al.  Observation of toroidal plasma rotation driven by the electric field induced by loss of ions , 1991 .

[9]  Y. Wang,et al.  H mode confinement in Alcator C-Mod , 1997 .

[10]  J. D. Bell,et al.  Rotation scalings and momentum confinement in neutral-beam-injected ISX-B plasmas , 1986 .

[11]  S. Migliuolo.  REVIEW PAPER: Theory of ideal and resistive m=1 modes in tokamaks , 1993 .

[12]  J. Rice,et al.  Five‐chord high‐resolution x‐ray spectrometer for Alcator C‐Mod , 1990 .

[13]  L. Panaccione,et al.  JET high resolution bent crystal spectrometer , 1989 .

[14]  B. Duval,et al.  Behaviour of plasma rotation and radial electric field with density ramp rate in an ohmically heated tokamak , 1992 .

[15]  S. Suckewer,et al.  Plasma rotation in the PDX tokamak , 1983 .

[16]  Harold P. Furth,et al.  Plasma Physics and Controlled Nuclear Fusion Research , 2007 .

[17]  Burrell,et al.  Role of edge electric field and poloidal rotation in the L-H transition. , 1990, Physical review letters.

[18]  T. Marshall,et al.  Observations of plasma rotation in the high beta Tokamak Torus II , 1983 .

[19]  Ulrich Stroth,et al.  Characterization of the angular momentum transport in ASDEX , 1991 .

[20]  E Kallne,et al.  Observations of toroidal plasma rotation induced by ICRH in JET , 1992 .

[21]  J. Connor,et al.  Toroidal rotation and momentum transport , 1987 .

[22]  N. Asakura,et al.  Toroidal rotation and ion heating during neutral beam injection in PBX-M , 1993 .

[23]  J. Rice,et al.  X-ray observations of central toroidal rotation in ohmic Alcator C-Mod Plasmas , 1997 .

[24]  J. Snipes,et al.  ICRF heating in the Alcator C‐Mod tokamak , 1996 .

[25]  C. Zheng,et al.  ; 0 ; , 1951 .

[26]  P. Bonoli,et al.  High power density H-modes in Alcator C-Mod , 1996 .

[27]  Rice,et al.  Precision measurement of the 1s Lamb shift in hydrogenlike argon. , 1986, Physical review. A, General physics.

[28]  L. Vainshtein,et al.  Energy Levels of He- and Li-Like Ions (States 1snl, 1 s2nl with n = 2-5) , 1985 .

[29]  P. T. Bonoli,et al.  First results from Alcator‐C‐MOD* , 1994 .

[30]  Wootton,et al.  Space potential distribution in the ISX-B tokamak. , 1986, Physical review letters.

[31]  I. V. Ivanov,et al.  Measurements of plasma column rotation and potential in the TM-4 tokamak , 1985 .

[32]  Glen W. Erickson,et al.  Energy levels of one‐electron atoms , 1977 .

[33]  Rice,et al.  Radial profiles of ground-state transitions of heliumlike argon from the Alcator-C tokamak. , 1987, Physical review. A, General physics.

[34]  L. Lao,et al.  Reconstruction of current profile parameters and plasma shapes in tokamaks , 1985 .

[35]  B. Saoutic,et al.  Impurity ion temperature and toroidal rotation velocity in JET from high‐resolution x‐ray and XUV spectroscopy , 1988 .

[36]  P. Diamond,et al.  Neoclassical poloidal and toroidal rotation in tokamaks , 1991 .

[37]  J. Rice,et al.  High resolution X-ray spectroscopy diagnostics of high temperature plasmas , 1985 .

[38]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[39]  E. C. Crume,et al.  Bifurcation theory of poloidal rotation in tokamaks: A model for L-H transition. , 1989, Physical review letters.

[40]  N. Peacock,et al.  Toroidal rotation in the DITE tokamak , 1985 .

[41]  K. Burrell,et al.  Confinement of angular momentum in divertor and limiter discharges in the Doublet III tokamak , 1988 .

[42]  Hill,et al.  Satellite spectra for heliumlike titanium. II. , 1982, Physical review. A, General physics.

[43]  S. Coda,et al.  Beyond paradigm: Turbulence, transport, and the origin of the radial electric field in low to high confinement mode transitions in the DIII-D tokamak , 1995 .

[44]  M. von Hellermann,et al.  Charge exchange spectroscopy measurements of ion temperature and toroidal rotation in JET , 1989 .

[45]  J. Rice,et al.  OBSERVATIONS OF ALCATOR C-MOD PLASMAS FROM A FIVE CHORD HIGH ENERGY RESOLUTION X-RAY SPECTROMETER ARRAY , 1995 .

[46]  Tait,et al.  Local measurements of correlated momentum and heat transport in the TFTR tokamak. , 1990, Physical review letters.