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Probing Astrophysically Relevant Atomic Processes on the Z Machine: the ZAPP Collaboration  

Physics/Astro Auditorium

Thomas Gomez (Sandia National Lab)

November 8 @ 4:00 PM - 5:00 PM

Sandia National Laboratories is one of three DOE NNSA research and development laboratories whose primary mission is stockpile stewardship. These laboratories engage in many research areas, including bio-engineering, alternative energy, inertial confinement fusion. The Z-machine facility at Sandia is the world’s largest X-ray generator and is used to study high-energy-density physics. The Z-facility is ideal for studying atomic physics in the same conditions as those observed in astrophysical objects; this is the foundation for the Z-Astrophysical-Plasma-Properties (ZAPP) collaboration. The collaboration (funded in part by the Wootton Center for Astrophysical Plasma Properties) is actively trying to seek solutions to several problems: “Is opacity responsible for the discrepancy between the standard solar model and helioseismology?”, “Is resonant Auger destruction (RAD) the reason why certain spectral lines are not observed in black-hole accretion disks?”, “How accurate are the current line-broadening models (of neutral hydrogen) that are used to determine white dwarf masses?”. The iron-opacity experiment has revealed that there may be an unknown source of opacity for Fe at the base of the solar convection zone; experiment and data analysis methods are currently under scrutiny. RAD has been shown to not be 100% efficient and we are currently working on more fully characterizing the physics behind RAD. The white-dwarf-photosphere experiment found consistency between models for the broadening of H-beta. However, there is an unexplained discrepancy between emission and absorption line shapes, and significant discrepancies on the modeling the high-n lines of hydrogen.