Weak focusing
![A particle bunch with position variance gets focused in a magnetic field. In reality, the beam will not get focused to a point, but keeps a finite spot size due to divergence.](/Images/godic/202502/20/Weak_focusing_dipole_sketch.svg3346.png")
Weak focusing occurs in particle accelerators when charged particles are passing through uniform magnetic fields, causing them to move in circular paths due to the Lorentz force. Because of the circular movement, the orbits of two particles with slightly different positions may approximate or even cross each other.