A simple boronization technique for T-3M and T-11M tokamak chambers

Abstract

A new technique for chamber boronization has been tested on tokanaks T-11M ( R = 0.7 m, a= 0.2 m, B t = 1 T, J p = 80 kA) and T-3M ( R = 1.06 m, a = 0.26 m, B t = 1 T, J p = 120 kA). This technique is not subject to drawbacks of conventional boronization, which makes use of the highly toxic and explosive gas diborane. The boron-containing gas was produced in the course of simple decomposition of ecologically safe and explosion proof solid substance in helium glow discharge for 2–3 h with the chamber wall at room temperature. In T-3M the graphite limiter and stainless steel wall and in T-11M the molybdenum wall and diaphragms were boronized. Despite the differences in wall and diaphragm structural materials the results produced by boronization were found to be similar. The radiation losses and effective ionic charge in the plasma were reduced. The critical density limit was increased by a factor of at least 3, and the loop voltage was decreased to 1 V. The hydrogen recycling was reduced after heat treatment or glow discharge conditioning. This simple, ecologically clean, hazard free and inexpensive boronization technique is recommended for extensive application in tokamaks.