A simple and inexpensive method to align toroidal modules in tokamaks

The stray magnetic fields in the cross-section of the discharge chamber of a tokamak, generated by an incorrect alignment of its toroidal modules are a drawback in the obtention of suitable intensity and duration of the plasm a current. In this work, a simple and inexpensive method to align toroidal modules in a tokamak is reported. This method is based on the use of magnet ic probes which determine the minor-radial component of the magnetic field of each toroidal module. The magnetic probes are placed in, at least, three points on the periphery of each module. The procedure was applied to Novil lo Tokamak where a significant reduction in the stray magnetic field was ac hieved, allowing us to obtain a more appropriate position for each one of t he 12 modules. Such adjustment provides experimentally the minimum attainab le value of the minor-radial component of the magnetic field. The stray fie ld was reduced by approximately 50% in the cross-section of the discharge c hamber. Due to the good results obtained as well as the simplicity and effe ctiveness of this inexpensive method, it is recommended for the alignment o f toroidal modules. (C) 1998 Elsevier Science B.V. All rights reserved.