JET turns 30 this year, but its smaller cousin Tore Supra, in France, is close behind, celebrating its 25th anniversary this month. Tore Supra was conceived even before JET's construction was complete with a view to surpassing JET's performance in specific areas - for example pulse length. And 25 years on, Tore Supra continues to look forward, with big plans to line it with tungsten (atomic symbol W) and install a divertor, in the WEST (W Environment in a Steady-state Tokamak) Project.
The great leap forward that Tore Supra incorporated was superconducting magnets. This enabled a much longer pulse length; indeed Tore Supra set the record for the longest pulse in a large tokamak - six minutes - in 2003*. While this is an achievement in itself, it also provides a vital tool for testing materials in a sustained plasma discharge. In particular, Tore Supra has been instrumental in exploring the active cooling of materials that face the plasma. Although it turned out that building a water-cooling system robust enough to weather the harsh environment of a tokamak has been a challenge, the knowledge gained will be vital for the long pulses of ITER.
A real triumph is that Tore Supra's superconducting magnets are still showing no sign of wear and tear. There has been only a single accident, when a brutal plasma stop triggered a quench i.e. a fast discharge of the current of the superconductor into external resistors. The emergency system worked perfectly and the magnet was made available again soon after the event.
The continued operation of the superconductors carries Tore Supra into its next reincarnation. ITER will also have superconducting magnets, and during the WEST project Tore Supra will be modified to add more similarities to the huge machine. On top of the tungsten lining and divertor, the new configuration will require a set of poloidal coils installed to be inside the vacuum vessel to enable a divertor plasma shape to be formed. New ion-cyclotron-resonant heating antennae will also be installed, along with additional diagnostic systems.
The WEST project was launched on March 7th, only a month or so before the anniversary of Tore Supra's first plasma, on April 2nd. A celebration for institutional, industrial and international collaborators with the IRFM took place on May 14th. On June 17th celebrations will culminate with an event at CEA Cadarache for the whole IRFM staff - celebrations that will add to the nostalgia of an anniversary the anticipation of a new era.
The Institut de Recherche sur la Fusion Magnétique, IRFM, within the Commissariat à l’Énergie Atomique et aux Énergies Alternatives, CEA, is the French Signatory to EFDA.
* The record for longest tokamak pulse ever is 5 hours 16 minutes, held by the 84 cm radius TRIAM-1M at Kyushu University in Japan