The DTT goal is the identification of a reliable solution for the extraction of the heat generated by the fusion process . 

Fusion is achieved by heating a gas of hydrogen isotopes up to temperatures of 100 million degrees – ten times the temperature in the Sun core. In these conditions electrons are not bound to nuclei and matter is in the plasma state, a superposition of a gases of charged particles (negative electrons and positive nuclei). Plasmas are confined by intense magnetic fields (100000 times larger than the average Earth magnetic field) in a donut shaped configuration called tokamak.

The power released in the form of alpha particles by fusion reactions in the core of the tokamak is transported down to an actively cooled component (the divertor) where it is extracted. The heat flux on the divertor can be very large, of the same order of the heat flux on the Sun! The divertor has to withstand harsh conditions and is one of the most critical components of a fusion system.

A solution for the divertor has been investigated in present experiments and will be implemented in ITER, the first experimental reactor to generate 500MW of fusion power. However, it is unclear at the moment if the solution implemented in ITER can be extrapolated to future power plants, since the amount of fusion power density released in a reactor will be much larger than in ITER. 

For this reason DTT will investigate innovative solutions for the heat extraction based on advanced divertor configurations and new materials such as liquid metals in conditions relevant to a fusion power plant. 

DTT will be flexible by design, in order to be capable to test divertor systems that are not yet conceived. 

The need of a dedicated facility to address these challenges was pointed out first back in 2012, when EFDA, the European Fusion Development Agreement, published the “European Fusion Roadmap”, updated by the EUROfusion Consortium in 2018. These documents were intended to provide a strategic vision toward the generation of electrical power by a Demonstration Fusion Power Plant (DEMO), by 2050. Mission n. 2 ("Heat-exhaust system") of the Road Map focused on alternative solutions to the problem of disposing the heat load.

After the establishment of the DTT consortium, the construction has started with the goal of having DTT in operation during this decade.