Novel diagnostics for Mobile Dust; from Space to Fusion Plasmas

A brief overview of the diagnostics for dust in fusion plasmas is proposed, followed by a discussion focused on novel methods developed recently. The use of aerogel (very light and porous) samples as dust collectors during tokamak discharges - a diagnostic method originally developed for cosmic dust studies. Recent experimental results obtained by these collectors in tokamaks and in space are compared. Fast dust particles (with velocities > 1 km/s relative to the aerogel sample) are collected, intact, both in space and during tokamak discharges. It is discussed how their velocities could be inferred from the craters and the tracks formed in the aerogel target. The presence of fast dust grains was suggested by typical signatures in the ion saturation current collected by electrostatic probes in the FTU tokamak, indicating the occurrence of dust impact ionization phenomena. Hypervelocity dust particles are particular harmful in fusion reactors based on the tokamak concept, since they can significantly contribute to the wall erosion. In a vein of the development of a specific diagnostic for such fast particles, a prototype of an electro-optical probe is discussed. Electrostatic probes, though from far to be considered as a novel diagnostic, can still offer new detection methods for dust. For instance, in quiescent laboratory or space plasmas, the presence of dust could be revealed by the analysis of the frequency spectrum of the density fluctuations measured by electrostatic probes. This document is composed of an abstract followed by the slides of the presentation