Rotation Velocity Profiles Research Articles

DIII-D physics analysis database

Since June 1986 the DIII-D tokamak has had over 16 000 discharges accumulating more than 250 Gbytes of raw data (currently over 30 Mbytes per discharge). The centralized DIII-D databases and the associated support software described earlier provide the means to extract, analyze, store, and display reduced sets of data for specific physics issues. The confinement, stability, transition, and cleanliness databases consist of more than 7500 records of basic reduced diagnostic data datasets. Each database record corresponds to a specific snapshot in time for a selected discharge. Recently some profile datasets have been implemented. Diagnostic data are fit by a cubic spline or a parabola by the in-house energy code to provide density, temperature, radiated power, effective charge (Zeff), and rotation velocity profiles. These fits are stored in the profile datasets which are inputs for the onetwo code which computes transport data.

DIII-D physics analysis database (abstract)

Since June 1986 the DIII-D tokamak has had over 16 000 discharges accumulating more than 250 Gbytes of raw data (currently over 30 Mbytes per discharge). The centralized DIII-D databases and the associated support software described earlier provide the means to extract, analyze, store, and display reduced sets of data for specific physics issues. The confinement, stability, transition, and cleanliness databases consist of more than 7500 records of basic reduced diagnostic data datasets. Each database record corresponds to a specific snapshot in time for a selected discharge. Recently some profile datasets have been implemented. Diagnostic data are fit by a cubic spline or a parabola by the in-house energy code to provide density, temperature, radiated power, effective charge (Zeff), and rotation velocity profiles. These fits are stored in the profile datasets which are inputs for the onetwo code which computes transport data.

Spectroscopic diagnostic for measurement of plasma rotation in the Texas Experimental Tokamak (TEXT)

Plasma rotational velocity measurements may be applied to the test of plasma theory, to the assessment of the effects of plasma perturbations, and as substitutes for electric field measurements. For these applications, we developed a plasma rotation diagnostic based on the measurement of the Doppler shift of impurity spectra. In ohmic plasmas, the measurement is complicated by the small size of the velocity induced line shift compared with the line width. To overcome this problem, our diagnostic system is configured to observe each of two plasma regions at several times during a single shot using a single array detector. This procedure can eliminate the need for a separate absolute wavelength calibration if the regions are properly chosen and can minimize the effects of detector noise and shot-to-shot plasma variation. The two chords selected for observation can be changed from shot to shot. The details of the novel optical system are described. As an example of the technique, rotational velocity profiles for ohmic plasmas perturbed by a radial, resonant magnetic field are presented.

Improvement of angular momentum confinement with density peaking on ASDEX

Toroidal rotation velocity profiles during neutral beam injection on ASDEX have been investigated by means of charge exchange recombination spectroscopy. For both co- and counter-injection of neutral beams the ratio of the injected power and the line averaged electron density is found to be an essential experimental, parameter for the central rotation speed. With counter-injection, a continuous rise of rotation velocity and density is observed, indicating strong improvement of angular momentum confinement. This improvement is found to be strongly correlated with the peakedness of the density profile. Simple model calculations of momentum transport indicate that the increase of momentum confinement with density peaking can be partly attributed to the variation of torque deposition with the shape of the density profile.

Nonlinear superposition of solutions to self-gravitating fluid equations

view Abstract Citations (1) References (4) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Nonlinear Superposition of Solutions to Self-gravitating Fluid Equations Amendt, Peter ; Lanza, Antonio Abstract An analytic procedure for nonlinearly superposing axisymmetric, stationary, self-gravitating solutions to Euler's equation or the Jeans equations to generate new and more general classes of solutions is presented. Two examples of the method are given. The first uses a nonlinear superposition of two Maclaurin spheroids to produce a large family of self-gravitating toroidal solutions of Euler's equation. The second example examines some possible consequences of the nonlinear superposition on galactic mass modeling studies based on the Jeans equations. It is shown that (1) regions of reduced stellar density may lead to local angular momentum enhancement and (2) a flat composite rotation velocity profile may be nonlinearly constructed from two or more mass components with decreasing rotation curves. Publication: The Astrophysical Journal Pub Date: February 1990 DOI: 10.1086/168414 Bibcode: 1990ApJ...350..597A Keywords: Euler Equations Of Motion; Fluid Dynamics; Galactic Rotation; Gravitation; Superposition (Mathematics); Angular Momentum; Poisson Equation; Star Distribution; Astrophysics; GALAXIES: INTERNAL MOTIONS; HYDRODYNAMICS; ROTATION full text sources ADS |

Charge exchange spectroscopy measurements of ion temperature and toroidal rotation in JET

The JET tokamak relies on an active charge exchange spectroscopy diagnostic for measurements of ion temperature, toroidal rotation velocity and impurity density profiles. It uses the neutral heating beams as diagnostic beams and provides measurements at eight to twelve radial positions simultaneously with a time resolution of about 100 ms. A description of the instrument is given, together with an analysis of the experimental data and an account of recent results. Profiles of ion temperature and rotation frequency, based on the carbon C VI n = 8 to n = 7 transition at 5290.5 Å, are presented for plasmas in the hot ion mode, for magnetic limiter plasmas, and for discharges where a locked MHD mode brings the plasma to rest despite continued neutral beam injection. H-mode to L-mode transitions are found to cause a collapse of the edge ion temperature and the toroidal rotation frequency within less than a sampling time of 12 ms. This time resolution is also sufficient to reveal ion heat pulses following sawtooth crashes.

High time resolution ion temperature profile measurements on PBX

Ion temperature profiles with a time resolution of 2–5 ms have been measured on the Princeton Beta Experiment tokamak (PBX) by charge-exchange recombination spectroscopy (CXRS) and a neutral particle charge-exchange analyzer (NPA). The sightlines of both diagnostics crossed the trajectory of a near-perpendicular heating beam, which enhanced the local neutral density (∝ signal strength) and provided spatial resolution. The time resolution of these two independent techniques is sufficient to see sawtooth oscillations and other magneto- hydrodynamic activity. Effects of these phenomena on the toroidal rotation velocity profile, vφ(r), are clearly observed by CXRS. For example, a sharp drop in the central vφ occurs at the sawtooth crash, followed by a linear rise during the quiescent phase. The NPA results are compared with those from CXRS.

Centrifugal instability in rotating shallow water and the problem of the spiral structure in galaxies

A new instability predicte by theory to occur in rotating shallow water in which the rotation velocity has a discontinuity, in a regime where the flow velocity exceeds the characteristics velocity of the waves, has been found experimentally. The instability develops when the radial gradient of the angular velocity across the discontinuity is negative; such an instability is likely to be responsible for the formation of the spiral structure in galaxies which have a similar rotational velocity profile.

Plasma ion temperature measurements via charge exchange recombination radiation

Spatially and temporally resolved plasma ion temperatures can be determined by measuring the Doppler-broadened line profiles of transitions excited by charge-exchange recombination reactions between fast hydrogen atoms and fully ionized low-Z ions. Plasma rotation velocity profiles can also be obtained. A sample result from the PDX tokamak using He+ radiation is presented, and expected line intensities for model cases for PDX and TFTR are calculated.