Electron density calculation based on Stark broadening of D Balmer line from detached plasma in EAST tungsten divertor

Abstract

Evidence and modeling of 3D divertor footprint induced by lower hybrid waves on EAST with tungsten divertor operations W. Feng, L. Wang, M. Rack et al. -A new experimental classification of divertor detachment in ASDEX Upgrade S. Potzel, M. Wischmeier, M. Bernert et al. -Inferring divertor plasma properties from hydrogen Balmer and Paschen series spectroscopy in JET-ILW B. AbstractThe electron density within the volume of the tungsten divertor of the Experimental Advanced Superconducting Tokamak (EAST) is calculated based on D ε line (396.9 nm) Stark broadening (SB) measurements. The quasistatic approximation is employed in the SB calculation of the D ε line. The influences of other broadening mechanisms on the calculation error of electron density have been evaluated. The SB method is applied to the study of spatial distribution and time evolution of the electron density in the W divertor. Two electron density bands are observed in the detached divertor plasma during an L-mode discharge sustained by low hybrid wave (LHW) heating, which could be related to the striated particle flux distribution induced by LHW. After the onset of detachment, the upper electron density band corresponding to outer strike point firstly increases then decreases, while the lower density band corresponding to striated particle flux increases continually although the electron densities from Langmuir Probes at the divertor plate keep a descending trend. This could indicate a downward movement of the radiation region that approximately moves along the magnetic field lines after the onset of detachment.

Investigation of multifaceted asymmetric radiation from the edge (MARFE) with impurity injection from the upper divertor on the Experimental Advanced Superconducting Tokamak

“…A detailed description of the multichannel visible spectroscopic diagnostic system for the upper divertor on EAST is given in [35]. The electron density in the upper divertor volume is calculated by a spectroscopic measurement of the Stark-broadened D ε line (396.90 nm) [36]. All the discharges discussed in this paper w ere set with the upper single null (USN) configuration.…”

“…It is observed on EAST that Xpoint MARFE further evolved into wall MARFE. As shown in The electron density profiles in the divertor region are analyzed using the Stark broadening method [36]. As shown in figure 7, there are two density bands ; one is near the lines of sight passing through the strike point (first density band) and the other is near the X point (second density band).…”

A dual-route optical emission spectroscopy diagnostic with wide spectral range and high wavelength resolution on HL-2A tokamak

“…Mao et al monitored the line radiation of W I to investigate the tungsten flux in the divertor of EAST [21]. By measuring the intensity ratio of C III and C IV, Koubiti et al obtained the electron temperature profile and showed the existence of a recombining zone around the X-point multifaceted asymmetric radiation from the edge (MARFE) in JT-60U [22]. Further, the high-resolution spectrometer of Alcator C-Mod was used to obtain the electron density by measuring the line shapes of the deuterium Balmer series [2].…”