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Ion temperature measurements in the tokamak scrape-off layer with high temporal resolution

Publication at Faculty of Mathematics and Physics |
2021

Abstract

We present a uniquely fast (10 mu s) ion temperature measurements in the tokamak edge plasma. Our approach is based on the sweeping of a ball-pen probe, where the ion temperature is obtained by fitting the electron branch of the corresponding I-V characteristic.

We have performed measurements on the COMPASS tokamak during L-mode discharge. The temperature histograms reveal a non-Gaussian shape with a high-temperature tail peaking at low values.

The fitted values of fast I-V measurements can be used to reconstruct (emulate) the slow swept I-V characteristic of a retarding field analyzer. The resulting ion temperature profile is nearly flat and provides a ratio of ion to electron temperature close to 1-2 in the vicinity of the last closed flux surface during L-mode discharges, as observed on other tokamaks.