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Confinement

Confinement refers to the methods used to contain hot plasma at the extreme conditions necessary for fusion reactions.

Definition

Section titled “Definition”

In fusion research, confinement is the process of containing plasma at temperatures of 100 million degrees Celsius or higher, preventing it from touching material walls which would instantly cool it and halt fusion reactions. The plasma must be confined long enough for fusion reactions to produce net energy.

Types of Confinement

Section titled “Types of Confinement”

Magnetic Confinement

Section titled “Magnetic Confinement”

Uses magnetic fields to contain charged plasma particles. The particles spiral along magnetic field lines, preventing them from escaping.

  • Tokamak - Donut-shaped with plasma current
  • Stellarator - Twisted coils, no plasma current

Inertial Confinement

Section titled “Inertial Confinement”

Uses powerful lasers or particle beams to rapidly compress and heat a small fuel pellet. The fuel’s own inertia keeps it together long enough for fusion to occur.

  • NIF (National Ignition Facility, USA)
  • Laser Megajoule (France)

Gravitational Confinement

Section titled “Gravitational Confinement”

How stars confine plasma using their immense gravity. Not practical for Earth-based reactors.

Energy Confinement Time

Section titled “Energy Confinement Time”

The energy confinement time (τE\tau_E) measures how well a device retains the plasma’s thermal energy. It is a crucial parameter in the Lawson criterion:

n⋅τE⋅T>3×1021 keV⋅s/m3n \cdot \tau_E \cdot T > 3 \times 10^{21} \text{ keV} \cdot \text{s} / \text{m}^3
Section titled “Related Terms”