The effects of the main parameters of the helicon plasma sources on the volume process of the negative ion production mechanism are investigated. Using COMSOL Multi-Physics software, a helicon plasma source as a source driver of a negative ion source is modelled in three dimensions. In this work, it is considered that the helicon plasma source employs a Nagoya-type antenna at an operational frequency of 13.56 MHz. The influences of the static magnetic field variation, applied radio frequency power and injected gas pressure on electron/plasma density, electron temperature and vibrationally excited molecular density are studied. Variations of the static magnetic field in a range of 0.01–0.08 T, Radio Frequency (RF) power in a range of 800–6000 W and gas pressure range of 0.3–1.5 Pa indicate that the maximum electron (plasma) density is increased in all three cases; nevertheless, the electron temperature and maximum density of the vibrationally excited molecules is increased just by RF power increment. For the pressure of 0.3 Pa, it is found that using a proper coil configuration, the electron density and the vibrationally excited molecular density will be increased without the magnetic field (applied DC power) increment and RF power increment.

Plasma in axisymmetric mirror traps is unstable versus flute-like modes if no stabilising measures are taken. Instead of stability it is also possible to aim at suppressing the convective transverse transport generated by unstable modes. A ‘vortex confinement’ scheme of this type is utilised in current operation regimes of the Gas-Dynamic Trap in Novosibirsk Bagryansky et al.(2011 Fusion Sci. Technol., vol. 59, pp. 31–35). The relevant model Beklemishev et al. (2010Fusion Sci. Technol., vol. 57, pp. 351–360) describes the effect as due to nonlinear interaction of the flute modes with the background sheared rotation induced by plasma biasing via end plates and limiters. The rigid $m=1$ mode is saturated only due to current dissipation at the end plates, i.e. the partial line tying. The original model assumes flat radial profiles of plasma density and electron temperature, neglecting possible centrifugal and electron-temperature effects. These sources of instability are added to the original framework using a single scalar forming its hybrid extension. Efficiency of the biasing scheme for nonlinear suppression of flute-like convection is shown to depend primarely on spatial positions of biased facility elements, rather than on additional sources of instability.

Inertial Alfvén waves are thought to accelerate electrons to auroral energies via their parallel electric field in the Earth’s magnetosphere. During active geomagnetic times, it is estimated that a significant percentage of electron precipitation energy into the Earth’s ionosphere can be attributed to these waves. However, self-consistent wave/particle interactions of inertial Alfvén waves with the accelerated electron population are not well understood. We show that recent self-consistent models have a strong nonlinearity in them. A reduced set of equations which describe this nonlinear steepening is derived and shown to agree with drift-kinetic simulations and other published studies. From this reduced set of equations, many properties of the nonlinearity are derived and shown to agree with simulations. This includes the time and length scales and connecting the speed of the wave to the perturbation maximum value.