Effects of Tungsten Radiative Cooling on Impurity, Heat and Momentum Transport in DIII-D Plasmas
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2026
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| author | Biwole, A. Tema Odstrčil, T. Litaudon, X. Shi, S. Ernst, D. Zimmermann, C. F. B. Lestz, J. Howard, N. T. Rodriguez-Fernandez, P. Khabanov, F. Turco, F. Perks, C. Manas, P. Fajardo, D. Kim, S. K. Schmitz, L. Wang, H. Boyes, W. Ding, S. Victor, B. Christal, C. Lasnier, C. Wilks, T. M. McKee, G. |
| author_facet | Biwole, A. Tema Odstrčil, T. Litaudon, X. Shi, S. Ernst, D. Zimmermann, C. F. B. Lestz, J. Howard, N. T. Rodriguez-Fernandez, P. Khabanov, F. Turco, F. Perks, C. Manas, P. Fajardo, D. Kim, S. K. Schmitz, L. Wang, H. Boyes, W. Ding, S. Victor, B. Christal, C. Lasnier, C. Wilks, T. M. McKee, G. |
| contents | A first-of-its-kind experiment was conducted in the DIII-D tokamak under WEST similarity constraints on plasma shape and core parameters. This work presents a detailed transport study comparing a reference regime dominated by intrinsic carbon radiation and a high-radiation regime resulting from controlled tungsten (W) injection using the Laser Blow-Off system, with a core tungsten concentration $n_{\mathrm{W}}/n_e \sim 3\times 10^{-4}$ and a radiated-power fraction $f_\mathrm{rad}>0.5$. The W-induced radiative cooling lowered the electron temperature, thereby decreasing $T_e/T_i$ and stabilizing trapped-electron-mode (TEM) turbulence. This transition in turbulence regime reduced momentum and ion thermal diffusivities, yielding ion temperature peaking and a factor-of-two increase in toroidal rotation. At the outer plasma region, enhanced $E\timesB$ shear and increased collisionality further suppressed ion-scale turbulence, causing a sharp drop in ion heat flux. Consequently, impurity transport, predominantly turbulent in the low-radiation regime, acquired a strong neoclassical inward W convection during radiative cooling, bootstrapping the cooling cycle. Despite $f_\mathrm{rad}>0.5$, radiative collapse was not observed, likely owing to collisional ion-to-electron energy exchange acting as an electron-energy reservoir, together with $1/1$ MHD activity modulating the radiated power through core impurity neoclassical $T_i$-screening. These results support preparation for a tungsten wall change in DIII-D by elucidating tungsten-induced turbulence stabilization. They also provide key insights for interpreting plasma performance in WEST and are relevant to future reactors expected to operate with radiating tungsten-walled plasmas. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_06096 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Effects of Tungsten Radiative Cooling on Impurity, Heat and Momentum Transport in DIII-D Plasmas Biwole, A. Tema Odstrčil, T. Litaudon, X. Shi, S. Ernst, D. Zimmermann, C. F. B. Lestz, J. Howard, N. T. Rodriguez-Fernandez, P. Khabanov, F. Turco, F. Perks, C. Manas, P. Fajardo, D. Kim, S. K. Schmitz, L. Wang, H. Boyes, W. Ding, S. Victor, B. Christal, C. Lasnier, C. Wilks, T. M. McKee, G. Plasma Physics A first-of-its-kind experiment was conducted in the DIII-D tokamak under WEST similarity constraints on plasma shape and core parameters. This work presents a detailed transport study comparing a reference regime dominated by intrinsic carbon radiation and a high-radiation regime resulting from controlled tungsten (W) injection using the Laser Blow-Off system, with a core tungsten concentration $n_{\mathrm{W}}/n_e \sim 3\times 10^{-4}$ and a radiated-power fraction $f_\mathrm{rad}>0.5$. The W-induced radiative cooling lowered the electron temperature, thereby decreasing $T_e/T_i$ and stabilizing trapped-electron-mode (TEM) turbulence. This transition in turbulence regime reduced momentum and ion thermal diffusivities, yielding ion temperature peaking and a factor-of-two increase in toroidal rotation. At the outer plasma region, enhanced $E\timesB$ shear and increased collisionality further suppressed ion-scale turbulence, causing a sharp drop in ion heat flux. Consequently, impurity transport, predominantly turbulent in the low-radiation regime, acquired a strong neoclassical inward W convection during radiative cooling, bootstrapping the cooling cycle. Despite $f_\mathrm{rad}>0.5$, radiative collapse was not observed, likely owing to collisional ion-to-electron energy exchange acting as an electron-energy reservoir, together with $1/1$ MHD activity modulating the radiated power through core impurity neoclassical $T_i$-screening. These results support preparation for a tungsten wall change in DIII-D by elucidating tungsten-induced turbulence stabilization. They also provide key insights for interpreting plasma performance in WEST and are relevant to future reactors expected to operate with radiating tungsten-walled plasmas. |
| title | Effects of Tungsten Radiative Cooling on Impurity, Heat and Momentum Transport in DIII-D Plasmas |
| topic | Plasma Physics |
| url | https://arxiv.org/abs/2604.06096 |