Boron and Boron Nitride Injection for Tungsten Source Control and Advanced Radiative Divertor Scenarios in DIII‑D

Boron nitride (BN) powder (45 μm, 25 mg/s) injected vertically into the DIII-D tungsten-coated small-angle slot divertor (SAS-VW) reduced peak parallel heat flux by up to 90%, demonstrating effective tungsten source suppression and power exhaust control via localized radiative cooling. BN raised divertor neutral pressure tenfold, triggering detachment and reducing W erosion. Compared to N₂ gas seeding, BN produced earlier detachment through localized low-Te (≤ 10 eV) radiation from boron and nitrogen, enhancing power dissipation near the target. Radiated power increased in the X-point region, consistent with N II emission and volumetric cooling. These effects accelerated detachment with minimal core impact at moderate injection rates. Pure boron powder (150 μm, 10–25 mg/s) reduced W leakage, halved midplane W deposition, and doubled local B deposition by altering surface composition and impurity transport. Effects stem from boron-induced cooling, frictional retention, and dilution of sputtering-sensitive surfaces. High-confinement (H₉₈ᵧ₂ = 1.0–1.2) was maintained with under 20% energy loss. LIBS confirmed B on lower divertor and midplane surfaces. Results support boron injection for W control in ITER and show BN powders' broader potential for power exhaust in future FPPs [1, 2].