JT-60 upgrade device for confinement and steady state studies

Abstract

This paper describes the upgraded JT-60. The objectives of this upgrade are to improve plasma performance with minimum modification and to obtain physical and engineering database for the design of next-step tokamaks. The original poloidal field coil system and vacuum vessel are exchanged for new ones with large D-shaped cross sections, which allow plasma current of up to 6 MA, plasma volume of up to 100 m3 and plasma elongation of 1.4 to 1.8 with single nuli divertor configuration. Other equipments like the toroidal field coils, heating systems and power supply systems are used after minor modification. A large vacuum vessel was designed to take fuli advantage of the volume inside the bore of the existing toroidal field coils: the chamber wali has continuously welded double-skin structure to reduce its thickness and to maintain its strength. A carbon-fiber composite with thermal conductivity of up to 300 W/m°C is used for the divertor plates to reduce carbon influx.