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Garud Snoep - Graduation thesis at DIII-D

For my Master’s thesis project I spent six months working in the Theory and Computational Sciences group at the DIII-D Tokamak National Fusion Facility in San Diego, California. The DIII-D Tokamak is operated by General Atomics for the US Department of Energy and is the largest magnetic fusion research experiment in the USA. This environment results in an amalgam of the focussed, goal-oriented, build-as-you-go philosophy of a company and the cutting-edge, curiosity driven, structured style of academic research. It was very motivating to work there with experts in the field.

At General Atomics a workflow coupling codes for predicting the steady state core plasma profiles (TGYRO) and the H-mode pedestal height and width (EPED-1) had been developed by Orso Meneghini. My assignment was to self-consistently couple this workflow to a code that could predict the steady-state impurity density profiles. Impurity transport is not included natively in TGYRO and both intrinsic and seeded impurities have a strong impact on the fusion performance of the plasma.

A further requirement was to keep the resulting workflow as fast as possible, such that the resulting tool might be used for in-between shot analysis of the steady-state part of a discharge in the future. Therefore, we used STRAHL, a fast 1D radial impurity transport solver, to simulate the impurity transport. To perform the coupling and integrated modelling simulations I wrote an automated workflow in the OMFIT framework, made contributions to the TGYRO and STRAHL modules and eventually even developed my own OMFIT module.

All this coding gave me plenty of opportunities to learn how to code in Python, some basic Fortran and how distributed software development using GitHub works. These are important tools in modern scientific computation.

I also got the opportunity to present the preliminary results of the workflow with a poster at the annual American Physical Society Department of Plasma Physics (APS-DPP) conference. This was an inspiring event since it is the biggest annual plasma physics conference in the US, thus providing a broad view of all the work that is going on in the field and opportunities to interact with other scientists in fusion research.

Overall the experience of living and working in Southern California for six months was amazing. My colleagues at General Atomics were very welcoming which really made me feel at home in San Diego. In particular I want to thank my daily supervisor Orso Meneghini for the opportunity and his guidance on the project. This internship and all the hiking, surfing and playing beachvolleybal in San Diego were made possible by the FuseNet internship grant I received, for which I am very grateful.