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Lidija Radovanovic - internship at IPP Garching

During last summer I had a chance to do an internship at IPP Garching, as a part of my master study in energy engineering. This was, however, not my first time in Garching. Only a year before I have visited the facility of ASDEX-Upgrade as a science tourist so to say. Back then I could not have imagined that in such a short period of time I would have an opportunity to be a part of the institute and work in such an exciting field of physics.

Ballooning and peeling modes

The first time I learned about the topic of my project, I found some of the terms to be familiar and some others… well not so much. Wrapping my head around these new concepts is a challenging and incredibly rewarding process that stretched far beyond the three months that I have spent there. I worked on the plasma edge stability. This is a very interesting and important topic in fusion plasmas, since the properties of the plasma edge strongly influence the performance quality of a discharge. Quasi-periodic losses of energy that appear in the outer-most region of the plasma scale with the size of the machine. This means that these turbulences, called edge-localized modes (ELMs), can be large enough to have a highly damaging impact in future larger tokamaks.

One of the possibilities to avoid their occurrence is to develop a regime with small ELMs that in a way softly stabilize the plasma. Understanding the transition between the two regimes was something that I looked deeper into. I did this by using a code named HELENA to analyse a discharge where this transition happens due to a change in the position of the plasma and one of the possible explanations is that the small ELMs are caused by particular type of instabilities that are driven by the pressure gradient that appears on the plasma edge. These instabilities are called ballooning modes. For the first few weeks of my stay in Germany their name also caused a lot of discussion and expressive hand-waving for people in my surrounding, since I was looking for a very clear, obvious and straightforward explanation to my question: Why are they called ballooning modes and their partners in crime, the current driven modes, are called peeling modes? Needless to say, several beautiful graphical solutions to this problem arose and I never looked at the party balloon and the peeling banana emoji the same way again.

Throughout this project I had a great luck to have not one, but three involved, supportive and helpful mentors who were always there for all of my silly and serious questions. The Max Planck Institute for Plasma Physics is a great institution and a very friendly environment. I met a lot of people at the institute and every single one of them made me feel welcome and free to just come up with a problem or a question without hesitation. Many social events make it very easy to connect with others, share some new experiences and make friends. It is definitely a wonderful feeling to be a part of such huge and positive team, working on the same exciting goal in so many different ways.

A beautiful environment

Spending the summer on the far edge of Munich was beyond my expectations. Garching is a small village in Bavaria, well-connected with the city. Being the last metro station, in only half an hour, one travels from a peaceful green area to the center of a vivid city. An alternative to the train is a 20-km bicycle ride through a forest by the river, which is an experience itself. There are many lakes close by, where I daily enjoyed some of the most beautiful sunsets and got back my long forgotten passion for swimming. In the neighboring town I visited the oldest beer brewery in the world, operating since 1040. Yes, almost a whole millennium. Spending a summer evening with friends in any of the many beer gardens that Bavaria has to offer, for me is a great way to finish a long day of doing all that science.

In November, after my project has finished, I got the honor to present the results of the work I did at the annual seminar of ASDEX Upgrade group, which takes place in a beautiful Ringberg castle. This opportunity added up on my already huge pile of unique experiences I have had thanks to this internship. My collaboration with IPP is still ongoing, since I am continuing to work on the analysis of ELMs with the HELENA code, virtually, from my home in Vienna. I would like to thank FuseNet, Max PlanckInstitute for Plasma Physics and Technical University of Vienna, for helping me pursue my dreams and explore the world of science in ways that I could not have imagined are possible.

- Lidija Radovanovic