Ion Heating and MHD Dynamo Fluctuations in the Reversed Field Pinch

Ion Heating and MHD Dynamo Fluctuations in the Reversed Field Pinch
Author:
Publisher:
Total Pages: 13
Release: 1992
Genre:
ISBN:

Download Ion Heating and MHD Dynamo Fluctuations in the Reversed Field Pinch Book in PDF, Epub and Kindle

Ion temperature measurements, time resolved to 10 [mu]s, have been made in the Madison Symmetric Torus reversed-field pinch with a five channel charge exchange analyzer. The ion temperature, T{sub i} ≈ 200 eV for I = 350 kA, increases by as much as 100% during discrete dynamo bursts in MST discharges. Magnetic field fluctuations in the range 0.5--5 MHz were also measured. Structure in the fluctuation frequency spectrum at the ion cyclotron frequency appears as the bursts terminate, suggesting that the mechanism of ion heating involves the dissipation of dynamo fluctuations at ion gyro-orbit scales.

Advances in Reversed Field Pinch Theory and Computation

Advances in Reversed Field Pinch Theory and Computation
Author:
Publisher:
Total Pages: 7
Release: 1992
Genre:
ISBN:

Download Advances in Reversed Field Pinch Theory and Computation Book in PDF, Epub and Kindle

Advances in theory and computations related to the reversed field pinch (RFP) are presented. These are: (1) the effect of the dynamo on thermal transport; (2) a theory of ion heating due to dynamo fluctuations; (3) studies of active and passive feedback schemes for controlling dynamo fluctuations; and (4) an analytic model for coupled g-mode and rippling turbulence in the RFP edge.

Energy Research Abstracts

Energy Research Abstracts
Author:
Publisher:
Total Pages: 782
Release: 1995
Genre: Power resources
ISBN:

Download Energy Research Abstracts Book in PDF, Epub and Kindle

Spectroscopic Measurement of the MHD Dynamo in the MST Reversed Field Pinch

Spectroscopic Measurement of the MHD Dynamo in the MST Reversed Field Pinch
Author:
Publisher:
Total Pages: 295
Release: 1998
Genre:
ISBN:

Download Spectroscopic Measurement of the MHD Dynamo in the MST Reversed Field Pinch Book in PDF, Epub and Kindle

The author has directly observed the coupling of ion velocity fluctuations and magnetic field fluctuations to produce an MHD dynamo electric field in the interior of the MST reversed field pinch. Chord averaged ion velocity fluctuations were measured with a fast spectroscopic diagnostic which collects line radiation from intrinsic carbon impurities simultaneously along two lines of sight. The chords employed for the measurements resolved long wavelength velocity fluctuations of several km/s at 8--20 kHz as tiny, fast Doppler shifts in the emitted line profile. During discrete dynamo events the velocity fluctuations, like the magnetic fluctuations, increase dramatically. The toroidal and poloidal chords with impact parameters of 0.3 a and 0.6 a respectively, resolved fluctuation wavenumbers with resonance surfaces near or along the lines of sight indicating a radial velocity fluctuation width for each mode which spans only a fraction of the plasma radius. The phase between the measured toroidal velocity fluctuations and the magnetic fluctuations matches the predictions of resistive MHD while the poloidal velocity fluctuations exhibit a phase consistent with the superposition of MHD effects and the advection of a mean flow gradient past the poloidal line of sight. Radial velocity fluctuations resolved by a chord through the center of the plasma were small compared to the poloidal and toroidal fluctuations and exhibited low coherence with the magnetic fluctuations. The ensembled nonlinear product of the ion velocity fluctuations and fluctuations in the magnetic field indicates a substantial dynamo electric field which peaks during the periods of spontaneous flux generation.

Dynamo and Anomalous Transport in the Reversed Field Pinch

Dynamo and Anomalous Transport in the Reversed Field Pinch
Author:
Publisher:
Total Pages: 27
Release: 1998
Genre:
ISBN:

Download Dynamo and Anomalous Transport in the Reversed Field Pinch Book in PDF, Epub and Kindle

The reversed field pinch is an effective tool to study the macroscopic consequences of magnetic fluctuations, such as the dynamo effect and anomalous transport. Several explanations exist for the dynamo (the self-generation of plasma current)--the MHD dynamo, the kinetic dynamo, and the diamagnetic dynamo. There is some experimental evidence for each, particularly from measurements of ion velocity and electron pressure fluctuations. Magnetic fluctuations are known to produce energy and particle flux in the RFP core. Current profile control is able to decrease fluctuation-induced transport by a factor of five. Improved confinement regimes are also obtained at deep reversal and, possibly, with flow shear.

Physics Briefs

Physics Briefs
Author:
Publisher:
Total Pages: 1334
Release: 1993
Genre: Physics
ISBN:

Download Physics Briefs Book in PDF, Epub and Kindle