Interpretation of flush-mounted probe current-voltage characteristics using four-parametric fits

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61389021%3A_____%2F19%3A00509576" target="_blank" >RIV/61389021:_____/19:00509576 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00216208:11320/19:10406964

Výsledek na webu

<a href="https://iopscience.iop.org/article/10.1088/1361-6587/ab3de8" target="_blank" >https://iopscience.iop.org/article/10.1088/1361-6587/ab3de8</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1088/1361-6587/ab3de8" target="_blank" >10.1088/1361-6587/ab3de8</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Interpretation of flush-mounted probe current-voltage characteristics using four-parametric fits

Popis výsledku v původním jazyce

The evaluation of probe measurements in the swept regime can be performed via a fit to the ion branch of the current-voltage (I-V) characteristic, providing the most relevant plasma parameters such as the ion saturation current, the electron temperature and the floating potential. In this paper, we present a parametric study based upon the existing flush-mounted probe setup briefly operated at the COMPASS tokamak, aiming to compare relevant I-V formulas widely used for such analysis. Selected four-parametric fit descriptions were applied to synthetic data obtained by simulation of the probe in a particle-in-cell model, SPICE, both in simplified 2D and more complex 3D geometries. Plasma parameters recovered by the fit were compared to the input from the model and the precision of this recovery was mapped to a wide range of parameters, especially with respect to the ratio of the probe size d pin to the Larmor radius r L. Results show that while the electron temperature and the floating potential can be obtained quite precisely regardless of the method, the ion saturation current can be identified incorrectly, mainly due to the fact that the sheath expansion description by optical approximation is not sufficient for almost grazing field line angles of incidence, especially when d pin ∼ r L. We show, however, that operation of flush-mounted probes can be fruitful especially in high-field devices. Additionally, we have explored the sensitivity on the available bias potential range, showing that for proper analysis of I-V characteristic using four-parametric fit, the lower bound of the fit range should be at least below the floating potential. If this condition cannot be satisfied, three-parametric fit in the range close to the floating potential can still produce results with acceptable precision.

Název v anglickém jazyce

Interpretation of flush-mounted probe current-voltage characteristics using four-parametric fits

Popis výsledku anglicky

The evaluation of probe measurements in the swept regime can be performed via a fit to the ion branch of the current-voltage (I-V) characteristic, providing the most relevant plasma parameters such as the ion saturation current, the electron temperature and the floating potential. In this paper, we present a parametric study based upon the existing flush-mounted probe setup briefly operated at the COMPASS tokamak, aiming to compare relevant I-V formulas widely used for such analysis. Selected four-parametric fit descriptions were applied to synthetic data obtained by simulation of the probe in a particle-in-cell model, SPICE, both in simplified 2D and more complex 3D geometries. Plasma parameters recovered by the fit were compared to the input from the model and the precision of this recovery was mapped to a wide range of parameters, especially with respect to the ratio of the probe size d pin to the Larmor radius r L. Results show that while the electron temperature and the floating potential can be obtained quite precisely regardless of the method, the ion saturation current can be identified incorrectly, mainly due to the fact that the sheath expansion description by optical approximation is not sufficient for almost grazing field line angles of incidence, especially when d pin ∼ r L. We show, however, that operation of flush-mounted probes can be fruitful especially in high-field devices. Additionally, we have explored the sensitivity on the available bias potential range, showing that for proper analysis of I-V characteristic using four-parametric fit, the lower bound of the fit range should be at least below the floating potential. If this condition cannot be satisfied, three-parametric fit in the range close to the floating potential can still produce results with acceptable precision.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10305 - Fluids and plasma physics (including surface physics)

Projekt

<a href="/cs/project/LM2015045" target="_blank" >LM2015045: COMPASS – Tokamak pro výzkum termonukleární fúze</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2019

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Plasma Physics and Controlled Fusion

ISSN

0741-3335

e-ISSN

—

Svazek periodika

61

Číslo periodika v rámci svazku

10

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

16

Strana od-do

105011

Kód UT WoS článku

000485695000001

EID výsledku v databázi Scopus

2-s2.0-85072713243