Nuclear Fusion: Reactor Cross-Section (2D)

What Nuclear Fusion Is

Nuclear fusion is the process by which atomic nuclei combine to form heavier elements, releasing vast amounts of energy in the process. This phenomenon occurs naturally in stars like our sun and can be harnessed on Earth for clean, sustainable power.

In a tokamak reactor, deuterium (D) and tritium (T) isotopes are heated to extremely high temperatures, causing their nuclei to overcome electrostatic repulsion and fuse. This fusion releases energy in the form of heat.

Key Parameters Affecting Fusion

The Lawson criterion is a key factor determining whether a tokamak can sustain a fusion reaction. It states that for sustained fusion, the product of plasma density (n), confinement time (τ), and energy confinement parameter (β) must exceed a certain threshold.

In this simulation, you control temperature, density, and confinement time to see how they affect the reactor's performance. Higher temperatures increase ion velocities, while higher densities enhance collision frequency, both crucial for fusion.

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Magnetic Confinement and Gyrokinetics

In a tokamak, magnetic fields confine plasma particles within the reactor's toroidal shape. The magnetic flux surfaces ensure that charged particles gyrate in tight orbits around field lines, preventing them from escaping.

Gyrokinetic theory is used to model these particle motions accurately. It accounts for the finite size of ions and electrons, their interactions with electromagnetic fields, and turbulence within the plasma.

Reactivity and Q-Factor

The reactivity (Q) factor is a measure of how efficiently energy is produced in a fusion reactor. A Q-factor greater than 1 indicates that more energy is released from the reaction than was input, making it self-sustaining.

In this simulation, you can observe changes in reactivity as you adjust temperature and density. The fusion flashes represent successful fusion events, with their frequency indicating the overall reactivity of the system.

Frequently asked questions

What is the Lawson criterion?

The Lawson criterion is a condition that must be met for sustained nuclear fusion in a tokamak reactor. It requires a balance between plasma density, confinement time, and energy confinement parameter to ensure sufficient fusion reactions occur.

Why are deuterium and tritium used in fusion reactors?

Deuterium and tritium are chosen because they have the lowest ionization energies among all elements, making it easier for their nuclei to fuse. Additionally, these isotopes produce high-energy neutrons that can be utilized or bred into more fuel.

How does magnetic confinement work in a tokamak?

Magnetic fields in a tokamak create a toroidal (doughnut-shaped) plasma. The magnetic flux lines confine charged particles within the reactor, preventing them from escaping and ensuring that fusion reactions can occur.

What does Q-factor represent in fusion reactors?

The Q-factor represents the ratio of energy output to input in a fusion reactor. A Q-factor greater than 1 indicates that the reactor is producing more energy than it consumes, making it self-sustaining and potentially viable for power generation.

Try it live

Everything above runs in your browser — open Nuclear Fusion: Reactor Cross-Section (2D) and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.

▶ Open Nuclear Fusion: Reactor Cross-Section (2D) simulation