The term “poloidal” refers to the component of a magnetic field or the movement of particles that is oriented along the direction of the magnetic lines of force in a toroidal (doughnut-shaped) geometry. In a tokamak or other similar magnetic confinement devices, the poloidal direction is the circular direction around the torus, running parallel to the “hole” of the doughnut.
In the context of a tokamak:
- Poloidal Magnetic Field: The poloidal magnetic field is the component of the magnetic field that circulates around the toroidal axis. It contributes to the confinement of the plasma and helps maintain its stability. Together with the toroidal magnetic field, the poloidal field creates a helical path for the charged particles in the plasma, preventing them from escaping.
- Poloidal Movement of Particles: When particles (such as ions and electrons) move along the circular path in the poloidal direction, they follow the curvature of the magnetic field lines. This movement is an essential part of the plasma confinement mechanism in a tokamak.
- Plasma Rotation: In a tokamak, achieving a certain level of poloidal rotation of the plasma is important for maintaining stability and preventing instabilities that could disrupt the plasma. Controlled plasma rotation can be used to improve plasma confinement and reduce the risk of disruptions.
- Plasma Shape: The poloidal shape of the plasma refers to the cross-sectional shape of the plasma column in the toroidal direction. Engineers and researchers carefully design and control the plasma’s shape to optimize stability and confinement.
In summary, “poloidal” is a term used in plasma physics and fusion research to describe the component of a magnetic field or particle movement that is aligned with the circular direction around the toroidal axis in a torus-shaped magnetic confinement device like a tokamak.