Development of Tungsten Materials for Plasma Facing Components in Japan

This paper reports Japanese activities on tungsten material development and the basic studies on plasma and tungsten interactions. Effects of helium ion irradiation on embrittlement and bubble formation of various tungsten materials have been intensively investigated in Japan. Details of the helium bubble formation mechanism, its effects on surface morphology ,and the impacts on dust formation are presented. Fine-grained and TiC fine-particles dispersed tungsten are being developed to increase the resistance of the material to degradation in the fusion reactor environment. Microstructures and specific features amenable to fusion environments are presented. The experimental results on repetitive heat pulses on surface roughening and cracking are shown. The repetitive heat pulse effects are very serious and further studies are needed. Important issues of tungsten material development for DEMO and commercial devices will be discussed.