Simulating Fusion Plasmas

Thomas Hayward-Schneider
Max Planck Institute for Plasma Physics (IPP)
Garching, Germany
EUM ’22,        27th January 2022

Disclaimer: these views are my own and do not reflect those of my employer.


  • Fusion
    • What is fusion?
    • How does it work?
    • Why do we care?
    • Why is it hard?
  • Tokamaks & ITER
  • Modelling
  • Outlook


  • “Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles”
    – Wikipedia: “Nuclear fusion”
  • An ideal and clean source of electricity
  • The process used by the Sun
  • It’s the “opposite” of Nuclear fission (which releases power by splitting big atoms)
  • Mass difference \(\Rightarrow\) \(E=mc^2\) \(\Rightarrow\) voila


  • Specifically, are there 2 small things which we can get to join together, Step ??? = Profit
  • Nuclei are + charged, repel each other
    • Must hit each other with high energy to convince them otherwise
  • “DT” wins: Deuterium (\(^2\)H) = heavy hydrogen; Tritium (\(^3\)H) = extra-heavy hydrogen
    • Gives us our target fusion reaction: \(^2\)D + \(^3\)T \(\Rightarrow\) \(^4\)He + \(^1\)n + 17.6 MeV
    • Peak at temperatures > 100 M °C

N.B. Different from the fusion process in the Sun


  • In summary:
    • Get some Deuterium and Tritium
    • Heat them to >100 M °C
    • Make sure they stay put
    • Fusion happens
    • Profit

Fusion & Plasma

  • Hydrogen at 100 M °C
    • c.f. solar core (15 M °C); solar surface (5000 °C)
    • Fusion labs are hottest places in the solar system
  • Plasma – 4th state of matter (solid, liquid, gas, plasma):
    • Gases break apart at very high temperatures / low densities
    • Electrons and ions separate \(\Rightarrow\) all particles in a plasma are charged!
      • Charged particles interact with electromagnetic fields
    • Most of “stuff” in space, plus the outer planets, is a plasma
  • A lot of fusion physics is plasmas physics

Idea: use magnetic fields to “hold” our plasma
\(\to\) Magnetic Confinement Fusion

“We say that we will put the sun into a box. The idea is pretty. The problem is, we don’t know how to make the box.”
Pierre-Gilles de Gennes

Magnetic confinement

Red: no magnetic field
Kicked particle flies away

Blue: magnetic field (into screen)
Kicked particle gyrates

Magnetic confinement