Limiter damage due to over-heat load in doublet III tokamak

Abstract

Two tiles of the primary limiter, which are composed of TiC coated Poco graphite, are heavily cracked during neutral beam heating experiment (beam power of 2 MW). These damages are considered to be caused by the thermal stress due to the over-heat load (2.3 kW/cm 2). The major disruption occurs after a rapid increase of the impurity influx following to the tile cracks. A base temperature of the limiter tile is over 300°C at the time of this accident. These kind of accidents are avoidable with a careful monitoring of the limiter temperature.