Plasma turbulence, suprathermal ion dynamics and code validation on the basic plasma physics device TORPEX

Abstract

The TORPEX basic plasma physics device at the Center for Plasma Physics Research (CRPP) in Lausanne, Switzerland is described. In TORPEX, simple magnetized toroidal configurations, a paradigm for the tokamak scrape-off layer (SOL), as well as more complex magnetic geometries of direct relevance for fusion are produced. Plasmas of different gases are created and sustained by microwaves in the electron-cyclotron (EC) frequency range. Full diagnostic access allows for a complete characterization of plasma fluctuations and wave fields throughout the entire plasma volume, opening new avenues to validate numerical codes. We detail recent advances in the understanding of basic aspects of plasma turbulence, including its development from linearly unstable electrostatic modes, the formation of filamentary structures, or blobs, and its influence on the transport of energy, plasma bulk and suprathermal ions. We present a methodology for the validation of plasma turbulence codes, which focuses on quantitative assessment of the agreement between numerical simulations and TORPEX experimental data.

Blob dynamics in the TORPEX experiment: a multi-code validation

“…(16)(17)(18)(19) can be recast in the GBS and BOUT++ form by expressing Ω, Γ and j ∥ in terms of the quantities evolved by these codes. Moreover, we note that it has been verified with the TOKAM3X code that, in the considered blob scenarios, the Boussinesq approximation has a negligible influence on the numerical results.…”

Millimeter-Wave Beam Scattering by Field-Aligned Blobs in Simple Magnetized Toroidal Plasmas

“…In this Letter, we report on the first direct measurements of millimeter-wave scattering by intermittent blobs in a simple magnetized torus (SMT). The experiments are carried out in the toroidal basic-plasma-physics device named TORPEX [24]. An antenna launches a mmw beam from the top of TORPEX through a plasma featuring blobs with statistical properties similar to those observed in tokamaks [25].…”

Uncertainty propagation by using spectral methods: A practical application to a two-dimensional turbulence fluid model

“…This results in helical field lines that wind around the toroidal vacuum vessel from the bottom to the top of the device. The SMT configuration, implemented in a number of basic plasma physics experiments such as TORPEX [22,23] and Texas Helimak [24], is of interest to the plasma physics community because it offers a simple and well diagnosed scenario to study the turbulent transport resulting from instabilities such as interchange modes and drift waves, which are present also in the tokamak SOL. In fact, models similar the the one used to investigate the SMT plasma dynamics have been used also for the tokamak SOL (see, e.g., Refs.…”