Problem of Characterization of Vacuum Vessel Shell for Spherical Tokamak Globus-M at Different Stages of its Fabrication

Abstract

Spherical tokamak shows considerable promise for the peaceful uses of thermonuclear energy in future. A number of spherical tokamak projects are developed in different research centers (MAST project at Culham Laboratory, UK, NSTX at Princeton University, USA, ETE, Brazil, GLOBUS-M, Russia etc.). Spherical tokamak GLOBUS-M¹ is under construction now at A.F. Ioffe Physico-Technical Institute, S. Petersburg. Its basic parameters are: plasma major radius 0.36m, plasma minor radius 0.24m, plasma current ≤0.5MA, toroidal magnetic field ≤0.62T. In all the projects the vacuum vessel is one of the most complex and critical part of the device. The overall dimensions of the shell are: diameter -1.96m, height — 1.85m. The large volume of the vessel, high requirements necessary for its final shape and sizes, for the mechanical properties of its material, as well as for magnetic ones generate a need for development of the special technological procedure of the vacuum vessel shell fabrication and methods of material state characterization and shape control at the different stages of the shell manufacturing. For their realization, a number of novel technological facilities was designed and made at the state enterprise “Leningradsky Severny Zavod (Northern Plant)”, Sankt-Petersburg, Russia. The developed procedure of spherical tokamak vacuum vessel shell fabrication and the control of its shape, sizes and material state is an example of application of nondestructive characterization methods to the real design of large weight and complex configuration.