Electromagnetic analyses for the design of a new active shell for RFX

This paper deals with the electromagnetic analyses carried out for the design of a new system developed to actively control the magnetic configuration of RFX. The system, which consists of a new conductive shell and a new set of saddle coils closely fitting the plasma region, is intended for replacing the present shell, keeping the existing vacuum vessel and principal coils of the machine unchanged. In the first part of the paper, the basic concepts representing the aims and the constraints of the system are described. Following this, the results of the electromagnetic analyses over the operating frequency range, performed by means of both analytical and finite element codes, are reported and discussed. The efficacy of the system is pointed out with the evaluation of the magnetic field generated by the new saddle coils and the reduction of field errors provided by the new shell with an overlapped gap. Finally, the calculation of the electrical parameters of the coils, taking into account the eddy current effect, is reported.