Joonas Govenius ’10



Project Title

Modeling Neutral Beam Heating in Fusion Reactors

Nuclear fission plants provide a stable and powerful source of energy, capable of producing large amounts of electricity compared to the size of the facility. However, fission plants suffer from the side effect of producing dangerous and extremely long-lasting radioactive waste in the process as well as posing a small risk of an uncontrolled reaction leading to an explosion. Nuclear fusion reactors are meant to remedy these most troublesome issues of current nuclear plants. When isotopes of hydrogen are combined to produce helium in fusion reactors, only small amounts of radioactive material is produced as the reactor components become activated. Furthermore, only small amounts of hydrogen are in the reactor at any given time so even an uncontrolled fusion chain reaction would not produce energy at dangerous rates.”

“The specific aim of my project was to model the so-called Neutral Beam Injectors (NBI) used in tokamak fusion reactors for heating up the hydrogen plasma. During the project I wrote a piece of software that reads in parameters describing an NBI system and produces a random sample of ionized particles from the neutral particle beam. Initially I spent a significant amount of time reading scientific papers about the topic in order to familiarize myself with plasma physics and, in particular, to find a good method for calculating the ionization rates inside the plasma. During the rest of the summer my time was taken almost entirely by implementation of the algorithm in Fortran code, and by data collection of the geometric parameters of the NBI system used in various tokamaks, such as ITER, JET, and AUG.

Overall, the internship was a great experience. The end result of the project was a simple but well-tested and functional module that can be used to create initialization data for programs that simulate what happens to the particles once they are ionized. I also enjoyed the atmosphere and excitement about fusion at the lab, so the experience certainly made me give more serious though to the possibility of returning to Finland to study fusion after graduating from Princeton.

Internship Year


Project Category

Climate and Energy


Advanced Energy Systems (AES), Helsinki University of Technology, Finland


Taina Kurki-Suonio