Simulating Fusion Plasmas
Thomas Hayward-Schneider
Max Planck Institute for Plasma Physics (IPP)
Garching, Germany
EUM ’22, 27th January 2022
@hattom
Disclaimer: these views are my own and do not reflect those of my employer.
Outline
- Fusion
- What is fusion?
- How does it work?
- Why do we care?
- Why is it hard?
- Tokamaks & ITER
- Modelling
- Outlook
Fusion
- “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
Fusion
- 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
Fusion
- 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
- So, along a straight magnetic field, particles stay on a line
- Build a cylinder, but what about the ends?
- No way to stop us losing particles at the ends
- Join the ends together
\(\to\) Torus
Magnetic confinement
- Aaaaaaaaaalmost problem solved
- Once we bend the ends, we no longer confine the plasmas
\(\to\) Introduce twist (helix) to magnetic field
Option 1: External helix
Build complex 3D magnetic coils
\(\to\) Stellarator
Option 2: “Internal” helix
Drive current through plasma, induce additional field
\(\to\) Tokamak
Tokamaks
- “тороидальная камера с магнитными катушками” /
“toroidal chamber with magnetic coils”
– Wikipedia: “Tokamak”
ASDEX Upgrade, © IPP, ixtract
Key Parts
Cross-section of ASDEX Upgrade (IPP)
- Magnetic coils
- D-shaped coils (toroidal field)
- Central solenoid (plasma current)
- Large circular coils (shaping)
- Vacuum vessel + pumps
- Plasma wall (heat loads)
- Heating systems (beams + radio waves)
- Diagnostics (measuring the plasma)
Fusion progress
Fusion progress
Fusion progress
- JET (DT) current record holder, 1997 campaign
\(Q_{plasma} = P_{out} / P_{in} = 0.65\)
- Few (2) tokamaks ran with “real” fusion fuel
- Most science done without tritium
- ITER goal:
\(Q_{plasma} \ge 10\)
- (Effective) size matters
- Linear dimensions:
ITER (global) \(\approx 2\times\) JET (Europe) \(\approx 4\times\) ASDEX Upgrade (Germany)
ITER
- ITER is Big Science
- Partners are: “China, the European Union, India, Japan, Korea, Russia and the United States”
– ITER Organization, iter.org
- Each partner contributes primarily in-kind
- e.g. India builds and delivers the cryostat
- …
- Makes total ITER cost impossible to say, but a ballpark figure of ~$20B is probably reasonable
- Located in Southern France
- Assembly already well progressed (see ITER website/YouTube channel for details)
- First plasma \(\approx\) 2025-ish
- Full power \(\approx\) 10 years later
- NOT a fusion power plant, but a demonstration of fusion at large scale (\(\approx 500\) MW\(_{th}\))
\(\to\) EU’s roadmap is ITER \(\Rightarrow\) DEMO \(\Rightarrow\) Power Plant
ITER
© ITER Organization, http://www.iter.org/
For scale: tiny human bottom right
ITER
