F. M. Poli

Basic turbulence studies on TORPEX and challenges in the theory-experiment comparison

TORPEX [A. Fasoli, B. Labit, M. McGrath, S. H. Muller, M. Podesta, and F. M. Poli, Bull. Am. Phys. Soc. 48, 119 (2003)] is dedicated to the study of electrostatic instabilities, turbulence, and transport. Plasmas are produced by waves in the electron cyclotron frequency range and are confined by a toroidal magnetic field of about 0.1T to which a small vertical component Bz is added. The crucial role of Bz for the basic confinement scheme through the generation of parallel flows has been studied previously. This paper focuses on the effects of Bz on turbulence. The observed strong dependence indicates an intrinsic coupling between average profiles, confinement, and turbulence regulated by the action of Bz. Two approaches to characterize turbulence are adopted, via time series statistics and via the direct measurement of spatiotemporal structures, made possible by the novel hexagonal turbulence imaging probe diagnostic, which is described in detail. Analysis methods to condense the large amount of data of s...

Probabilistic analysis of turbulent structures from two-dimensional plasma imaging

A method is presented to construct object-related structure observables, such as size, mass, shape, and trajectories from two-dimensional plasma imaging data. The probability distributions of these observables, deduced from measurements of many realizations, provide a robust framework in which the fluctuations, the turbulence, and the related transport are characterized. The results for imaging data recorded in the presence of drift-interchange instabilities and turbulence on the TORPEX toroidal plasma experiment [A. Fasoli et al., Phys. Plasmas 13, 055902 (2006)] are discussed.

Fast ion source and detector for investigating the interaction of turbulence with suprathermal ions in a low temperature toroidal plasma

A specific experimental apparatus consisting of an ion source and a detector for the investigation of the interaction between suprathermal ions and drift-wave turbulence is developed on the toroidal plasma experiment. Due to the low plasma temperature (similar to 5 eV), a spatially localized, small-size ion source (similar to 4 cm) mounted inside the vacuum vessel with relatively low ion energy (similar to 100 eV-1 keV) can be used. The source consists of an aluminosilicate Li-6 ion emitter (6 mm diameter, 10-30 mu A current) installed on a two-dimensional (2D) poloidally moving system. The location, energy, and current density profile of the ion beam will be measured using a 2D movable gridded energy analyzer. (c) 2006 American Institute of Physics.