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‎FY2018 NSTX-U Facility and Diagnostic Milestones‎

F(18-1):  Evaluate PFC operational limits and develop integrated diagnostic plans for operations

Description:  The NSTX-U Recovery Project is developing new plasma-facing components (PFCs) for use in the divertor of NSTX-U. The extreme conditions of the NSTX-U divertor make it possible to stress even graphite surfaces to the material limits leading to the possibility of component failures. In addition, the complex, mixed-material environment of the NSTX-U due to the use of boron and lithium wall conditioning techniques creates significant uncertainties in the monitoring of the PFCs. To assist in planning for initial and high-performance operations, it is advantageous to determine the design limits that will ensure reliable operation. It is also necessary to assess and redesign several edge-plasma diagnostic systems that must integrate with the new PFC designs. The goals of this milestone are three-fold: (1) test stress-limited PFC design features (potentially to destruction) and test high-temperature plasma-surface interactions that might result in operational temperature limits using e-beam and linear plasma-materials test facilities, respectively, (2) redesign boundary diagnostics and actuators affected by PFC design modifications (e.g. Langmuir probes, gas injection, spectroscopic views, or IR thermography), and (3) assess and develop the technical and engineering basis needed to effectively measure and monitor the performance of the PFCs, based on experimental test results.

(Incremental) Diagnostic Milestone ID(18-1): Install and commission Far Infrared Tangential Interferometer / Polarimeter diagnostic system

Description:  A new Far Infrared Tangential Interferometer / Polarimeter (FIReTIP) will be installed on NSTX-U and commissioned. The FIReTIP system was developed by UC Davis to measure line-averaged plasma densities. This system uses a carbon dioxide laser to pump a methanol laser to create the far infrared beam needed for NSTX-U plasma densities. The system includes a new real-time vibration compensation capability to enable the FIReTIP signals from a central chord to be used for future real-time density feedback control. Commissioning activities will include insuring that the lasers and data acquisition capabilities are operational for the FIReTIP diagnostic, and testing of the vibration compensation system. This milestone will only be carried out if sufficient resources are available.