Experimental Particle Transport Coefficient Evaluation in the Pedestal Region Utilizing Lyman-alpha Measurements

New high resolution measurements of main chamber Lyman-α radiation in the pedestal region have allowed direct evaluation of the Deuterium (D) or Hydrogen particle source for quantitative experimental examination of pedestal particle transport on DIII-D. Absolutely calibrated brightness measurements from the Ly-α Measurement Apparatus (LLAMA) allow quantitative evaluation of ionization rate and neutral density profiles. Using 1D geometry the particle fluxes and effective diffusion coefficient (Deff) can be evaluated from the ionization rate profile. During stationary periods in discharges, decreasing D_eff from ∼0.1-0.01 m²/s is observed as the density pedestal increases due to  varied plasma current and edge opacities. LLAMA has also been utilized to monitor the source during dynamic events such as ELMs and gas puff modulation. During ELM cycles, for ∼5 ms after the ELM onset, LLAMA measurements show increased D neutral density inside the separatrix while the electron density pedestal gradient is reduced. Then the density gradient saturates while the pedestal top electron density continues to evolve which is accompanied by increased ionization rate in the confined plasma region.