Conference paper

Investigation of suprathermal ion transport in TORPEX

In burning plasmas, fast ions may be generated by ion cyclotron resonance heating, neutral beam injection and fusion reactions. Fast ions will be responsible for a significant fraction of plasma heating and, in some scenarios, non-inductive current drive. Fast ions are also present in natural plasmas, such as the solar corona or the magnetosphere, where they are presumably accelerated by wave-particle interactions. The high temperatures of tokamak plasmas and the huge spatial scale of astrophysical plasmas make measurements of the fast ion transport very challenging. Basic plasma devices offer the possibility to study the interaction between fast ions and plasma turbulence with easy access for diagnostics and well-establish plasma scenarios. Experiments in the linear plasma device LAPD have shown that fast ion transport is increased in presence of turbulent or coherent electrostatic waves and that it is generally nondiffusive [1]. Basic aspects of fast ion transport in ideal interchange-mode unstable plasmas are investigated in the simple toroidal plasma device TORPEX. The magnetic field configuration of TORPEX consists of a toroidal component (Bt = 75 mT) and a smaller vertical component (Bv = 2 mT), resulting in helical open field lines, with grad-B and curvature. With this magnetic geometry, the fast ion motion without plasma is a combination of the gyromotion along the field lines and the vertical grad-B and curvature drifts.

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