The RFX (Reversed Field Experiment) device entered into operation in 1992. Since then, it has produced more than 10.000 pulses of ~100 ms with toroidal plasma currents of ~1.1 MA, with significant results in the fields of MHD physics, transport mechanisms and turbulence control. The substantial progress obtained in the understanding of the Reversed Field Pinch (RFP) plasma physics has led to significantly new knowledge and to design improvements of the machine for further research development.

In December 1999, a fire developed in a capacitor bank of the RFX device, destroying or damaging part of the power supplies. Euratom, CNR and ENEA, the organizations financially supporting RFX in agreement with Padova University, confirmed the importance of the RFX research programme and, thanks to the fact that the insurance company covered most of the cost of restoration, the RFX reconstruction and improvement plan became a reality.
Now the power supplies of RFX have been restored and modifications are being introduced:

• to improve the capability for active MHD control, via an array of 192 saddle coils outside the vacuum vessel;
• to improve the axysymmetric equilibrium control, by means of a thinner and closer shell;
• to widen the toroidal field control scenarios by a modified power supply system.

The utilisation of the most recent technologies in power semiconductors has allowed an expansion in the toroidal field power supply flexibility, which is particularly useful for MHD mode studies. The total energy stored in capacitors has been decreased and the bank has been divided into 12 separate modules to improve the current control in each coil sector and to facititate fault protection.

Industry has been centrally involved in the technological developments necessary to meet these requirements. Two examples of significant results are related to the new switching power supplies that use IGCT – a power semiconductor recently introduced in the market – and to the fast make switches based on Light Triggered Thyristor – instead of ignitrons – for capacitor bank discharge and for protective crowbars.

The poloidal field power supply and control system is presently being used to test the performance of new switches for ITER Fast Discharge and Protection Units.

The design and fabrication of the new components and systems were carried out with involvement of primary European companies:

• ASI Robicon, Milan (Italy)
• Siemens AG, Erlangen (Germany)
• Passoni&Villa, Milan (Italy)
• EEI S.p.A., Vicenza (Italy)
• Tesla, Storrington (UK)
• Babcock Noell Nuclear, Würzburg (Germany)
• Man Turbomacchine De Pretto, Schio (Italy)
• Le Carbone Lorraine, Parigi (France)
• Plansee, Reutte Tirol, (Austria)

It is now expected that RFX will return to operation in spring 2004 and the first physics experiments are planned for summer 2004. The scientific programme for the exploitation of the machine, which is in preparation, will be oriented towards obtaining a better understanding of confinement processes and, thanks to the better definition of the structure of the magnetic field, towards the reduction of the plasma-wall interactions and the possibility of actively influencing the transport. It will allow a deeper understanding of basic non-linear MHD phenomena such as magnetic reconnection, self-organisation and mode-mode interaction relevant to a large variety of plasmas. The modifications introduced will also provide continuity with the past research program, but, at the same time, will strongly improve the capability of addressing key issues relating to active MHD control.

The scientific programme of RFX will include important studies which are relevant not only to the RFP line, but to the entire magnetic fusion programme and in particular to tokamaks and ITER.

More information on Consorzio RFX: