JET is the current fusion device closest to ITER, sometimes referred to as “little ITER”. As a matter of fact, the experimental results and design studies performed by JET are consolidated to a large extent into the ITER design. In the past years, JET was upgraded to become even more ITER-like. It now features various unique capabilities to support ITER in a dedicated way.
The ITER-Like Wall
Normally the vessel walls of fusion experiments are lined with carbon, a material that withstands extreme heat stress. However, carbon shows an affinity for hydrogen, which is an issue for future fusion devices which operate with deuterium-tritium plasmas. In these machines retention of the radioactive and extremely rare tritium must be avoided. Metal walls made of beryllium and tungsten are the solution. JET now features an ITER-Like Wall made of these materials. It enables scientists to study the interaction of the plasma with these wall materials and – in combination with upgraded heating systems – to develop plasma operation scenarios for ITER.
Upgraded heating systems
To be able to investigate advanced plasma operation scenarios as planned for ITER, JET’s Neutral Beam Heating system has been upgraded to deliver up to 35 Megawatts.
JET is equipped with a High Frequency Pellet Injector, which is capable of shooting 50-60 deuterium ice pellets per second into JET plasmas. Pellet injection fulfills two purposes: fueling the plasma deep in the core and mitigating potentially harmful plasma edge instabilities, so-called ELMs. Finding ways to predict and mitigate ELMs is essential for ITER operations, as is finding efficient ways to fuel the fusion plasma.
Enhanced Diagnostic Systems
JET’s diagnostic and plasma control systems have been upgraded for two reasons. Firstly, to gather more detailed data for developing plasma scenarios for ITER and secondly to protect the newly installed ITER-Like Wall from the high heat loads caused by the plasma.
JET is the only operating fusion device licensed for handling tritium and therefore capable of conducting experiments with deuterium-tritium plasmas. The powerful D-T plasmas will be the fuel for fusion power plants and ITER will ultimately operate with D-T plasmas. During its last high power D-T campaign in 1997, JET produced a world record amount of fusion power. With the recent upgrades JET has become a much more ITER-like machine and can therefore test D-T operation with similar plasma scenarios as ITER.