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Luca Spinicci - MSc thesis at CCFE

I spent seven months working at Culham Centre for Fusion Energy (CCFE), where the tokamak JET is, working at my Master Thesis. I have been mostly improving and debugging a software aimed at issuing a benchmark of a model dealing with the plasma edge instabilities against experimental time series coming from the magnetic diagnostics of JET.

A model on ELMS

The model tries to reproduce the shape of the plasma edge instabilities and in particular the Type-I Edge Localised Modes (ELMs): ELMs are sudden eruptions from the edge of the plasma and Type-I ELMs may lead to confinement degradation and ablation of the divertor in a device as large as ITER. The key idea behind the model is to understand how much of the shape of the ELMs can be derived just from simple symmetry arguments.

Moreover, this is a simplified model which has the advantage of being computationally agile and so usable in a real time feedback device. In order to do so the discrete-time experimental observations must be handled as they come and fitted throughout the model forecasts to give a reasonable guess of the state of the system at every time. Producing such a guess is called an “assimilation” and it is exactly what our software does. The tools I have been learning about mainly concern the physics of the ELMs and the Bifurcation Theory for what concerns the model. The software is based on a Bayesian assimilation method called Ensemble Kalman Filter (EnKF), which required some notions of Bayesian Statistics and some reading on the EnKF itself. As the code is written in Python, also some preliminary training on this language was required.

Working in Culham...

I was supervised by a researcher of the CCFE – Dr. Wayne Arter – who is also the author of the model to whose future validation I contributed. This was the first interesting point in going to Culham: I had a stunning occasion to see how the actual research is performed. Culham is strongly recommendable also because it is full of young students mostly coming from the main English universities and so I could find many young researchers and a well-equipped environment, very much adequate to host a Master student on a Thesis (friendly people, cheap canteen, shared office with own computer…). Thirdly, the location is really enjoyable because – luckily enough – there is no spare room to live in Culham village. This was a wonderful chance to share a household in Oxford, where many young and very different people can live together.

...and living in Oxford

Just in my house there were two professionals from China and Venezuela, a PhD from Mexico and a Postdoc from the USA (and two rabbits: the only British minority in the house). Being somehow forced to live with and talk to people whose stories were so different from my one is perhaps the most important heritage of this experience. Now I know something of very different ways of living, of thinking, of the variety of troubles and joys that affect your life if you are born here rather than there.

Also, being in Oxford from April to November allowed me to fully enjoy the outdoors: Oxford has many parks and river Thames spreads into many small canals where on sunny days I liked going punting. Not last, every house has a backyard: in particular I managed to grow some beans and three giant sunflowers (all facing the neighbour’s garden, unfortunately - see below). On evenings, I would hang out with colleagues at pubs (there are many and some are really beautiful) or go to public lectures. Once in a while, especially when I had guests I would have cream tea with scones which is a must-do if you go to England.

I am very thankful to FuseNet, EUROfusion and the European Union itself for this wonderful chance to meet different points of view and learn more about this interesting European Country.

- Luca Spinicci