Effect of edge biasing on electrostatic fluctuations and particle transport in a nonfusion magnetoplasma

Abstract

This paper concerns experiments about the role of a radial electric field on the plasma turbulence in a toroidal magnetoplasma, and the possibility of anomalous transport reduction through the application of external biasing potentials to the plasma edge. The experiments show, for positive applied bias potential, a progressive reduction of radial anomalous particle flux, as well as electrostatic fluctuations. Some results on statistical and spectral properties of plasma and density fluctuations are reported.

Modification of electrostatic fluctuations by externally imposed radial electric fields

“…Thus, the plasma poloidal rotation in the edge region is characterized by high rotation velocities, with strong variations of both signs and values, which may have important effects on the electrostatic fluctuations. It is even possible to find a range of frequencies that can be decorrelated by polarization if we calculate the shear rate of the electric field; for the positive biases observed in our experiments, it appears to be of the order of about 50 kHz, which corresponds exactly to the frequency range where electrostatic fluctuations appear to be strongly reduced (further measurements of anomalous transport Riccardi et al (2000) seem to confirm this result).…”

RF-induced electric field and transport: experiments in non-fusion plasmas

“…One solution is to directly apply radial electric fields by means of biased limiters [6,7], while another is to launch waves into the plasma [8,9]. Plasma biasing induces electric fields mainly in the plasma edge, in the vicinity of the biased limiter [10]. By launching waves, the generation of the radial electric field is driven by nonlinear effects, i.e.…”

Edge biasing and its impact on the edge and SOL turbulence

“…It uses ñ and Ẽy in real space by the following description; where C nE y (0) is the zero-time correlation coefficient between ñ and Ẽy . We have used equation (20) for the calculation of the particle flux. Now, we will describe ñrms , Ẽy(rms) , and C nE y (0) with different biasing cases.…”

“…Several authors have studied the effect of biasing in the edge or SOL region. The biasing in these regions can be done in several ways e.g., divertor biasing [8][9][10][11][12], limiter biasing [13][14][15][16], emissive probe biasing [17,18], and electrode biasing [19][20][21][22][23][24][25][26][27][28]. An experiment carried out on the ISTTOK tokamak has shown [29] that electrode biasing in the edge region is more effective in comparison to limiter biasing.…”