Sandia National Laboratories Boundary Physics Research at DIII-D

Significant work has been done at DIII-D to support Sandia's boundary physics R&D, including upgrades to the fixed Langmuir Probe (LP) array diagnostic as well as developments on passive in-situ witness samples and active Pd-MIS charge-exchange (CX) sensors. Upgrades and maintenance on the LP array were completed over the past year to support measurements of target plasma conditions, including an overhaul of the system electronics, installation of 24 probes in the new shape and volume rise divertor, and expansion of the lower divertor shelf array from 9 to 20 probes. Witness samples with macroscopically textured surfaces have been installed at the first wall in DIII-D to investigate the roles of ion and neutral particle fluxes on material erosion and redeposition. New Pd-MIS CX sensors are being developed which incorporate microelectromechanical systems-based shutters for improved performance (longer life / time resolution). Piggyback testing of these devices is planned in the DIII-D divertor material exposure system over the next year.