We present a numerical and experimental study characterizing transport in laboratory plasmas with... more We present a numerical and experimental study characterizing transport in laboratory plasmas with various levels of magnetic chaos. Data have been taken in the MST and RFX Reversed Field Pinches. We focus on Single Helicity (SH) and Quasi-SH plasmas. In the theoretical SH state the RFP dynamo has a non-turbulent character. Self-organized stationary QSH regimes, where the spectrum of m=1
The response of electrons in a collisionless plasma to a fast‐rising voltage step is investigated... more The response of electrons in a collisionless plasma to a fast‐rising voltage step is investigated experimentally and theoretically. At small amplitudes the step generates a wave train, the leading edge of which propagates along the column at the long‐wavelength electron plasma wave velocity. At large step amplitudes a fast burst of electrons is observed, with kinetic energy roughly proportional to the step amplitude, followed by a nonlinear electron plasma wave signal which shows solitonlike behavior.
The trajectories of neutral beam injected energetic ions in spherical tokamaks are examined. The ... more The trajectories of neutral beam injected energetic ions in spherical tokamaks are examined. The large poloidal magnetic field in the outboard region of spherical tokamaks causes neutral beam injected ions to be born on trapped orbits even with cotangential injection. Numerical solutions to the equations for particle motion and for guiding center drifts are compared in several magnetic equilibria for a range of particle initial conditions. Even when rL/a∼1/4 the guiding center orbits closely resemble the path of the instantaneous center of gyration of the particle motion; exceptions occur primarily for orbits near the trapped/passing boundary. Finite Larmor radius effects are included in guiding center simulations of prompt orbit loss in the National Spherical Tokamak Experiment (NSTX) [J. Spitzer et al., Fusion Technol. 30, 1337 (1996)]. Orbit loss in the NSTX is caused primarily by collisions with the close fitting conducting shell, and severe losses would be expected with counter directed injection. Wh...
We present a numerical and experimental study characterizing transport in laboratory plasmas with... more We present a numerical and experimental study characterizing transport in laboratory plasmas with various levels of magnetic chaos. Data have been taken in the MST and RFX Reversed Field Pinches. We focus on Single Helicity (SH) and Quasi-SH plasmas. In the theoretical SH state the RFP dynamo has a non-turbulent character. Self-organized stationary QSH regimes, where the spectrum of m=1
The response of electrons in a collisionless plasma to a fast‐rising voltage step is investigated... more The response of electrons in a collisionless plasma to a fast‐rising voltage step is investigated experimentally and theoretically. At small amplitudes the step generates a wave train, the leading edge of which propagates along the column at the long‐wavelength electron plasma wave velocity. At large step amplitudes a fast burst of electrons is observed, with kinetic energy roughly proportional to the step amplitude, followed by a nonlinear electron plasma wave signal which shows solitonlike behavior.
The trajectories of neutral beam injected energetic ions in spherical tokamaks are examined. The ... more The trajectories of neutral beam injected energetic ions in spherical tokamaks are examined. The large poloidal magnetic field in the outboard region of spherical tokamaks causes neutral beam injected ions to be born on trapped orbits even with cotangential injection. Numerical solutions to the equations for particle motion and for guiding center drifts are compared in several magnetic equilibria for a range of particle initial conditions. Even when rL/a∼1/4 the guiding center orbits closely resemble the path of the instantaneous center of gyration of the particle motion; exceptions occur primarily for orbits near the trapped/passing boundary. Finite Larmor radius effects are included in guiding center simulations of prompt orbit loss in the National Spherical Tokamak Experiment (NSTX) [J. Spitzer et al., Fusion Technol. 30, 1337 (1996)]. Orbit loss in the NSTX is caused primarily by collisions with the close fitting conducting shell, and severe losses would be expected with counter directed injection. Wh...
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