SOLID TARGET BORONIZATION IN THE TOKAMAK DE VARENNES - A TECHNIQUE FOR REAL-TIME BORONIZATION

A new boronization technique, called solid target boronization (STB), has been developed and successfully applied in the Tokamak de Varennes. For this technique, a boronized carbon-carbon composite material is used as a source of boron and is exposed directly to confinement plasmas in order to induce boron emission due to thermal evaporation and sputtering. The STB technique can provide real-time boronization effects by implementing self-reconstructing boron-carbon coatings. A significant decrease in impurity radiation due to oxygen as well as several metals has been observed. Also, the fuelling rate increases considerably during STB, which is attributed to codeposition of carbon, boron and hydrogen.