Tokamaks represent a leading approach in magnetic confinement fusion research, designed to replicate the conditions within stars to generate energy. These devices employ a toroidal (doughnut-shaped) vacuum chamber where a plasma of light atomic nuclei, typically deuterium and tritium, is heated to extreme temperatures, exceeding 100 million degrees Celsius. At these temperatures, nuclei overcome their electrostatic repulsion and fuse, releasing significant energy. The confinement of this superheated plasma is achieved through a complex system of magnetic fields, preventing it from touching the chamber walls and cooling down. Source: Iter

The magnetic field configuration in a tokamak is crucial for plasma stability and confinement. It comprises three main components: a toroidal field generated by external coils, a poloidal field created by a current flowing within the plasma itself, and a vertical field to control the plasma's position. This intricate magnetic cage is essential for maintaining the plasma's integrity for durations long enough to facilitate fusion reactions. The plasma current, a key feature of tokamaks, not only contributes to the magnetic confinement but also helps in heating the plasma through ohmic heating, similar to how a resistor heats up when current flows through it. Source: Iter

The magnetic field configuration in a tokamak is crucial for plasma stability and confinement.

Achieving sustained fusion requires meeting specific plasma performance criteria, often summarized by the Lawson criterion. This criterion relates the plasma density, temperature, and confinement time, indicating the minimum conditions necessary for a fusion reaction to produce more energy than is consumed to maintain it. While many experimental tokamaks have demonstrated plasma confinement and achieved fusion conditions, the challenge lies in sustaining these conditions for extended periods and achieving a net energy gain (Q > 1). The development of advanced materials and superconducting magnets has been critical in pushing the boundaries of plasma performance. Source: Iter

ITER, the International Thermonuclear Experimental Reactor, is currently the world's largest tokamak project, aiming to demonstrate the scientific and technological feasibility of fusion power on a large scale. Its design goal is to achieve a fusion power output of 500 MW (thermal) from a 50 MW input, resulting in a Q-plasma of 10. Successful operation of ITER is expected to provide invaluable data and operational experience for future fusion power plants, paving the way for commercial fusion energy. The project involves collaboration between 35 nations, underscoring the global effort to realize fusion power. Source: Iter

Beyond ITER, numerous other tokamak experiments worldwide are contributing to fusion science, exploring different aspects of plasma physics, magnet technology, and operational regimes. These include devices like JT-60SA in Japan, JET in the UK, and various national laboratory experiments. The ongoing research focuses on improving plasma stability, reducing energy losses, and developing efficient methods for heating and current drive. The ultimate goal is to transition from experimental machines to commercially viable fusion power reactors that can provide clean, abundant energy. Source: Iter