Electrostatic Ion Cyclotron Instability Research Articles

Onset, growth, and saturation of the current-driven ion cyclotron instability

The temporal evolution of the current-driven electrostatic ion cyclotron instability was investigated experimentally. The critical destabilizing electron drift velocity for different values of mode phase velocity was measured. The phase velocity was changed by varying the effective plasma column length and hence the parallel wavelength. Ion cyclotron damping was observed to dominate over electron Landau damping at low phase velocities. The temporal growth rate was experimentally determined for several values of electron drift and found to agree very well with linear theory. The observed saturated mode amplitudes compare favorably with the saturation levels predicted by a theory of nonlinear stabilization due to wave induced collisions.

Evidence that the electrostatic ion cyclotron instability is saturated by ion heating

Observations have been made of electric field oscillations near the local ion gyro frequency and of an intense beam of plasma ions at the edge of an auroral arc. The observations are in good agreement with ion heating as the saturation mechanism for electrostatic ion cyclotron waves.

Ion Heating by the Current-Driven Electrostatic Ion-Cyclotron Instability.

Ion Heating by the Current-Driven Electrostatic Ion-Cyclotron Instability.

Ion Heating by the Current-Driven Electrostatic Ion-Cyclotron Instability

We have observed and confirmed significant ion heating by the electrostatic ion-cyclotron instability in a barium plasma. We present spectroscopic evidence showing that this mechanism drastically alters the velocity distribution, demonstrating at least a highly nonlinear process and giving strong evidence for randomization of the particle motion. Experimental corroboration of a theory of Drummond and Rosenbluth is presented.

Electrostatic Ion Cyclotron Instability Due to an Ion Beam in a Plasma

Experiments were carried out in which a 3–5 keV helium ion beam was injected into a low-density helium plasma along a pulsed magnetic field. Low-frequency waves growing in the direction of the beam flow were observed for the magnetic field strengths of 300–2000 G, which were characterized by the oscillation frequency in excess of the ion cyclotron frequency but less than the ion plasma frequency. The wave mode was axisymmetric and the radial wavenumber was much larger than the axial one. Axial wavelength measurements on launched waves suggested that the phase velocity of the growing wave was nearly equal to the ion beam velocity. Most of the experimental results were found to be consistent with a simplified theory of electrostatic ion cyclotron instability in a slow-beam plasma system, which however predicted larger growth rate than that measured.

Convective and absolute ion cyclotron instabilities in homogeneous plasmas

The properties of electrostatic ion cyclotron instabilities which can exist in mirror confinement machines are examined theoretically. Instabilities which are caused by an arbitrary combination of the loss-cone effect and the temperature-anisotropy effect are considered for an infinite plasma. The propagation characteristics (absolute or convective) of this class of instabilities are determined by numerical and analytical methods for interesting ranges of plasma parameters. Criteria on the length and lifetime of the plasma necessary for the growth of convective and absolute modes are deduced. The application of these results to present- and future-generation mirror machines is discussed.