Abstract Details
Abstracts
Author: Ray S Mattes
Requested Type: Consider for Invited
Submitted: 2025-01-29 15:41:24
Co-authors: L. Casali, T. Osborne, A. Leonard, H. Wang2, F. Laggner, M. Groth, C. Lasnier, A. McLean
Contact Info:
University of Tennessee Knoxville
Knoxville
Knoxville, TN 37996
United States
Abstract Text:
Dedicated H-mode hydrogen experiments have been conducted at DIII-D and are compared to similar deuterium plasmas under a range of divertor conditions, revealing significant effects of ion mass on divertor and pedestal conditions. H-mode confinement is found to be systematically lower in hydrogen and experiences a worse degradation with increased fueling. This coincides with a higher nesep in hydrogen for similar fueling rates. When neped is matched in hydrogen and deuterium as are the ne and Te pedestal structures while the target conditions deviate strongly from each other even under these conditions. Pedestal stability and neutral fueling analysis shows they are not sufficient to explain the pedestal differences between isotopes. Hydrogen and deuterium density ramps demonstrate a 20% higher ion current at detachment onset in hydrogen which occurs at similar upstream densities for both isotopes. The characteristics of target heat flux and divertor radiation are found to change significantly in each divertor operational regime with isotope mass. Interpretive SOLPS-ITER modeling of the experimental density scans, including particle drifts and matched upstream profiles, has been conducted. Alterations to the ionization source distribution with isotope mass contributes to a higher nesep in hydrogen for a given fueling rate. A significant portion of this particle source occurs near the midplanes. The source on the high field side trends in opposite directions for both isotopes through the density scan, indicating a strong role of drift-induced divertor asymmetries. A cooler inner target allows for variations in the ratio of reflected atoms to desorbed molecules with the isotope mass to be expressed, resulting in this deviation. Initial modeling with tritium, as well as the implementation of tungsten walls, further demonstrates that the interplay between isotope mass and the wall material has significant implications for divertor and pedestal conditions.
Characterization: 2.0
Comments: