Effects of Boronization in LHD

抄録

Boronization (boron coating) using diborane was carried out in the Large Helical Device (LHD) for wall conditioning. Using three nozzles for the diborane supply, about 60 % area of the vacuum chamber was covered by boron film. Oxygen impurity radiation was strongly reduced by gettering, and radiation from carbon and metals were reduced about 30 - 40 % by coverage with boron film. As a result, radiation loss was reduced and the operational density exceeded 1×10²⁰ cm^-3, which is about twice of that before boronization.