Relation between the plasma flow velocity and ion collection of Mach probes

Experiments on the HBT-EP (High Beta Tokamak-Extended Pulse) tokamak provided local measurements of the pressure and ion velocity perturbations from rotating magnetic island using Mach probes. The presence of magnetic islands created two distinct features in ion fluid velocity measurements. First, the toroidal velocity profile was sharply peaked near the center of the 2/1 magnetic island. Second, the ion velocity near this island was only ~30% of the magnetic island velocity. Measurements of the perturbations from rotating magnetic islands with stationary detectors prompted the development of a new data analysis technique using the Hilbert transform. This method generated plots of the pressure profile co-rotating with the magnetic island, allowing the analysis of the pressure profile behavior at the O and X-points of the magnetic island. Experiments with active rotation control demonstrated that the pressure perturbations followed the magnetic island motion, while simultaneously measuring that the ion velocity and acceleration were less that those of the magnetic island. These observations agreed with predictions from a two-fluid plasma model that included the effect of magnetic islands on the diamagnetic velocity as well as neutral damping effects. Understanding the effect of magnetic islands on the pressure and ion velocity profiles is crucial for both fundamental plasma studies and the development of more efficient tokamaks using advanced tokamak (AT) concepts.

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Effect of magnetic islands on the local plasma behavior in a tokamak experiment

Taylor

Cates

Mauel

et al. 2002

Physics of Plasmas

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Measurements of velocity shear and ion viscosity profile in a magnetohydrodynamic plasma jet

et al. 2010

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Time-dependent, two-dimensional profiles of the axial flow velocity, density, electron temperature, and magnetic field components are measured at two axial locations in a screw pinch plasma column of the reconnection scaling experiment. The results show that the ion momentum flux for a given column radius is dissipated by the ion-ion Coulomb scattering viscosity due to a significant radial shear of the axial velocity. By comparing the terms of the magnetohydrodynamic momentum balance equation, radial profile of ion viscosity is determined. Chord-integrated ion temperature measurements performed at several radial locations using Doppler broadening spectroscopy show ion temperature of about 1 eV. Measured ion viscosity agrees within a factor of 2 with the classical Braginskii expectations.

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Observation of cross-field plasma rotation in CDX-U using a simple Mach probe

Armstrong

Darrow

1994

Nucl. Fusion

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Relation between the plasma flow velocity and ion collection of Mach probes

Cited by 3 publications

References 9 publications

Effect of magnetic islands on the local plasma behavior in a tokamak experiment

Effect of magnetic islands on the local plasma behavior in a tokamak experiment

Measurements of velocity shear and ion viscosity profile in a magnetohydrodynamic plasma jet

Observation of cross-field plasma rotation in CDX-U using a simple Mach probe

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