Calibration of toroidal visible bremsstrahlung diagnostics and reconstruction of effective charge profiles in Korea Superconducting Tokamak Advanced Research (KSTAR)

Juhyeok Jang; Dongcheol Seo; Jong-Ha Lee; Ha Jin Kim; Jekil Lee; Won-Ha Ko; Yong Un Nam

doi:10.1063/5.0176471

Calibration of toroidal visible bremsstrahlung diagnostics and reconstruction of effective charge profiles in Korea Superconducting Tokamak Advanced Research (KSTAR)

Rev Sci Instrum. 2024 Jan 1;95(1):013503. doi: 10.1063/5.0176471.

Authors

Juhyeok Jang¹, Dongcheol Seo¹, Jong-Ha Lee^{1

2}, Ha Jin Kim¹, Jekil Lee^{1

2}, Won-Ha Ko^{1

2}, Yong Un Nam¹

Affiliations

¹ Korea Institute of Fusion Energy, 169-148 Gwahak-ro, Yuseong-gu, Daejeon 34133, Republic of Korea.
² Department of Plasma and Nuclear Fusion, UST-KFE School, 169-148 Gwahak-ro, Yuseong-gu, Daejeon 34133, Republic of Korea.

PMID: 38206099
DOI: 10.1063/5.0176471

Abstract

The investigation of impurity behavior in fusion plasmas is a critical issue in fusion plasma research. The effective charge (Zeff) profile is a widely used measure of the impurity levels in fusion plasmas. In this study, the visible bremsstrahlung emissivity profile is reconstructed using toroidal visible bremsstrahlung (TVB) arrays at Korea Superconducting Tokamak Advanced Research (KSTAR). KSTAR TVB arrays have recently been developed and calibrated using a halogen light source and an integrating sphere. The reconstruction algorithm has been developed using the Phillips-Tikhonov method, and the reconstruction accuracy is assessed with test profiles. Electron density and temperature profiles from Thomson scattering diagnostics are fitted for Zeff calculations. Subsequently, the Zeff profiles in the edge localized mode suppression experiment are reconstructed. In addition, line-averaged Zeff values in the 2020 KSTAR campaign are presented, which are mostly distributed from two to four.