Divertor Ion Temperature Measurements at DIII-D and Its Impact on Divertor Heat Flux

The divertor retarding field energy analyzer (RFEA) at DIII-D tokamak has been constructed and tested on the Divertor Material Evaluation System (DiMES) to measure ion temperature (T_i) at the lower divertor target. Initial L-mode test results show strong correlation between the current measured by the divertor RFEA and the ion saturation current measured by the Langmuir probe at the same radial location. Expected current magnitude, evaluated with particle-in-cell (PIC) simulations based on actual experimental conditions, is within a factor of two of the probe signals, which is likely due to slight misalignment of the RFEA components. The scale of effects of T_i on plasma-facing component’s (PFC) heat load, when decoupled from electron temperature, is evaluated through modeling tools. The sensitivity of the heat flux profile to divertor T_i is examined through edge plasma code SOLEDGE3X [1]. It has been demonstrated with the Heat flux Engineering Analysis Toolkit (HEAT) that the heat flux on optically shadowed PFC geometry due to finite ion gyroradius is significant [2], and the T_i-dependency of this effect is further explored in this poster.

[1] H. Bufferand et al., Nucl. Mat. Energy 18 (2019)

[2] T. Looby et al., Fusion Sci. Technol 78(1) (2022)

​​​​Work supported by the Department of Energy under Award Number(s) DE-SC0023378 and DE-FC02-04ER54698.