neutral-beam current drive

Neutral-beam current drive is a technique used in fusion reactors to sustain a steady-state electric current within the plasma. This is crucial for maintaining the plasma's stability and confinement.1

The process involves injecting a beam of high-energy neutral atoms into the plasma. Because they are neutral, these atoms can pass through the magnetic field without being deflected. Once inside the plasma, they collide with electrons, becoming ionized. These newly formed energetic ions are then trapped by the magnetic field and travel toroidally. Through further collisions, these ions push the electrons, creating a net directional movement, which is the electric current.1

While effective, neutral-beam current drive is not very efficient, requiring significant power to drive the plasma current. Other methods, like radio-frequency current drive, also exist, and a phenomenon called the bootstrap current can spontaneously arise in tokamak plasmas, reducing the need for external current drive. Plasma heating, often to around 100,000,000 K, is also essential for fusion reactions to occur, and neutral-beam injection is one method used for this purpose.12