Vito Konrad Zotta - MSc thesis at JET (CCFE)

I am a Master student in Energy Engineering at “Sapienza” University of Rome, the thesis is born in the framework of the well assessed collaboration between the ENEA of Frascati, the Sapienza University and JET (Joint European Torus) European Experiment. During the four month of stay at the Culham Science Centre I learned to use JETTO, a transport code that is the core of the JINTRAC suite, in order to model different plasma scenarios for the next JET’s experimental campaigns, both in deuterium (DD) and in deuterium-tritium (DT) plasma mixtures.

The Integrated Modelling through JET’s Experiments toward ITER scenarios

The JET is the largest and the most powerful Tokamak experiment, currently it is also the only experimental machine that can operate with a DT plasma mixture. The ITER experiment is still under construction and is expected to start plasma pulses in the 2025, although its DT operations are expected around the 2035 with the aim to reach a gain factor Q = 10. Different research groups around the world are working in parallel to develop and explore the ITER scenarios starting from the experimental data produced at JET, due to its similarity to ITER. JET has planned the experimental activities in DD (for the 2019) and in DT (for the 2020) in this framework of studies. Since 2011 JET is equipped with a beryllium (Be) first wall and with a tungsten (W) divertor. These components are of the same composition of the designed ITER’s plasma facing components, then the next JET’s experimental campaign DTE2 will happen in the closest conditions to ITER.

The main scientific goals planned for the experimental, theory and modelling activities related to the DTE2 campaign can be summarised in:

  • Demonstrating high fusion power of 15 MW for 5s;
  • Demonstrating clear alpha particle effects;
  • Clarifying the isotope effect on energy and particle transport;
  • Exploring the consequences of mixed plasma species;
  • Addressing key plasma-wall interaction issues;
  • Demonstrating ITER-relevant ICRF schemes;
  • Demonstrating ITER-like integrated plasmas;

My thesis work is strictly related to these activities from the modelling point of view, three groups of simulations have been performed in a fully predictive way in order to develop four different baseline scenarios with a moderate normalized beta. As mentioned, the simulations have been developed using JETTO as transport code, that is a plasma fluid code, coupled with QuaLiKiz as transport model, that is a physics-based model. The first group of simulation was carried out on an existing JET shot, the experimental data have been imposed as initial conditions while a scan has been done on different boundary conditions. The agreement between the simulated quantities (e.g. the electron density and temperature profiles) and the experimental data, mainly obtained from the High Resolution Thomson Scattering (HRTS), is computed with different performance indicators, for each simulation, in order to obtain the best set of free parameters for the models validation against the experimental results. With the best set of free parameters, doing a Greenwald Scaling, the second group of simulations was carried out in DD operations at higher current IP, higher toroidal magnetic field BT, and with higher additional heating power. The third group of simulations consists of the extrapolations for the DT scenarios by changing the plasma isotope mixture, using the same methodology.

Between work and relaxation

Attending the Culham Science Centre, it is very easy to keep in touch with other students and researchers working on a wide range of topics and coming from different countries. It is possible to join many talks, meetings and workshops daily organized at the research centre. It should be also mentioned the CCFE PhD students’ group that is very active and interesting both inside and outside the Science Centre. Moreover, Oxford is a very nice City and can offer to the visitors many interesting activities, concerts and events to rest and recover the energies to continue their studies and cultivate their interests.

- Vito Konrad Zotta