Analysis of the temperature influence on Langmuir probe measurements on the basis of gyrofluid simulations

TL;DR

This study uses gyrofluid simulations to analyze how temperature and its fluctuations affect Langmuir probe measurements of ion saturation current and floating potential in turbulent fusion plasma edges.

Contribution

It provides a detailed comparison between raw plasma parameters and probe-derived quantities, highlighting the impact of temperature fluctuations on measurement accuracy.

Findings

Significant discrepancies between raw data and probe-inferred quantities due to temperature fluctuations.

Fluctuation-induced radial particle flux calculations are notably affected by temperature variations.

Simulation results emphasize the importance of accounting for temperature effects in probe diagnostics.

Abstract

The influence of the temperature and its fluctuations on the ion saturation current and the floating potential, which are typical quantities measured by Langmuir probes in the turbulent edge region of fusion plasmas, is analysed by global nonlinear gyrofluid simulations for two exemplary parameter regimes. The numerical simulation facilitates a direct access to densities, temperatures and the plasma potential at different radial positions around the separatrix. This allows a comparison between raw data and the calculated ion saturation current and floating potential within the simulation. Calculations of the fluctuation-induced radial particle flux and its statistical properties reveal significant differences to the actual values at all radial positions of the simulation domain, if the floating potential and the temperature averaged density inferred from the ion saturation current is used.