Two million amperes. The 2010 experimental campaign of the RFX-mod reversed field pinch (RFP) experiment will also be remembered as a result of this number. It represents the maximum plasma current designed for the device, which has now been achieved for the first time.

RFX-mod is the largest RFP experiment in the world. It is based at Consorzio RFX in Padova and belongs to the EURATOM fusion program. For RFPs, the electrical current that flows in the plasma is a key operational and physics parameter. It heats the RFP plasma, which does not use auxiliary heating systems. Moreover, several fundamental physics properties of the configuration depend on the level of current. In particular, increasing the current improves the confinement and brings out new and appealing features, for example, improved helical states (See FN October 2009).

The machine is designed to produce a maximum plasma current of two megaamperes (MA). Over the last couple of years extensive operation has allowed plasma regimes to be optimised at around 1.5 – 1.7 MA. A number of new results have been obtained, opening up promising perspectives for further improvement of confinement.

One of the key missions of RFX-mod is the detailed exploration of RFP performance in the megaampere range, which requires extensive experimental activity at the maximum possible plasma current. For this reason, and thanks to the high intrinsic flexibility of the device, a number of operational tools have been successfully designed and commissioned during 2010, for example, the reconfiguration of the power supply. Moreover, thorough work has been carried out on the process of setting up plasma, i.e. on all those processes involved in bringing the plasmaup to its final state, and on the optimisation of the magneto hydrodynamic stability active control.

These efforts led, toward the end of the 2010 campaign, to the first successful plasma shot at 2 MA, demonstrating that the machine can be operated at such high currents in a safe manner and without major problems. Given the robust design of RFX-mod this was to be expected, but seeing it in practice is very encouraging. Now the machine is ready for exploration work at 2 MA. A task which is very challenging, since a number of points, for example density control, need to be tackled in order to achieve best performance. But the results obtained so far, in particular on the helical state and the reliability of the device, show that our ambitious goals for 2011 and beyond are realistic.

As in recent years, the 2011 RFX-mod campaign will be launched with a public call of proposals. In addition RFP exploration at high current, the main pillars of the RFX-mod science program will contribute to the development of two main topics in the field of magnetic confinement fusion: Magnetohydrodynamic stability active control and three-dimensional physics. The research will be conducted in strong partnership with tokamak and stellarator programmes and fully integrated into the EU fusion programme. More information on the call for proposal will appear on the Consorzio RFX website


Piero Martin, Consorzio RFX