The Observation of Tungsten Unresolved Transition Arrays Spectra at High Electron Temperature in Experimental Advanced Superconducting Tokamak (EAST) Plasma

Abstract

To optimize the plasma performance of fusion devices using tungsten plasma-facing components (PFCs), it is crucial to study the transport of tungsten impurities. This work focuses on the observation of line emissions from various charge states of tungsten ions in high-temperature plasmas utilizing Extreme Ultraviolet (EUV) spectrometers. Line emissions from W²⁶⁺-W³²⁺ ions are observed in the 45-55Å band at electron temperatures below 2.0 keV, while line emissions from W³⁴⁺-W⁴⁵⁺ ions appear in the 55-70Å band at electron temperatures above 3.0 keV. Additionally, radial profiles of W-UTA spectra in plasma with different electron temperature show that as the electron temperature decreases from 5.0 keV to 3.0 keV, the peak position of W²⁶⁺-W³²⁺ions move inward from ρ~ 0.5 to ρ~0.2. The line intensity profiles of W⁴²⁺-W⁴⁵⁺ ions accumulate within a narrow region of plasma core, specifically at ρ < 0.4. This study provides essential experimental data to support further research on tungsten impurity transport, control of tungsten content, and the enhancement of plasma performance.