Boronization System for the NSTX-Upgrade Fusions Device

Authors: D.Cai, W. Blanchard, M. Cropper, C.H. Skinner

Abstract: Boronization has been widely used as a key vacuum interior wall conditioning method to improve plasma performance in fusion devices. In this paper we report on a new boronization system designed and built for the NSTX-Upgrade fusion device (NSTX-U). Deuterated trimethylboron (C3D9B) is used to produce a thin boron containing coating on plasma-facing components (PFCs) via a glow discharge with vessel pressure maintained in the 1.5-2.0 millitorr range. This hard protective coating reacts with active molecules and reduces the amount of impurities observed in the plasma. Deuterated trimethylboron (dTMB) is a toxic and pyrophoric gas and great care must be used in the handling of this hazardous gas. Details of this new system are described which include enhanced equipment and operational safety, programmable logic controller (PLC) control of the process, improved equipment maintenance and serviceability, and increased operating pressure range and process flexibility. Results from boronization using this newly developed system will also be covered at the end of this paper.

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