Quadrupole Lens
Model ID: 829
Just like optical lenses focus light, electric and magnetic lenses can be used for focusing beams of charged particles.
This COMSOL Multiphysics model shows the path of B5+ ions passing through a focusing system of three magnetic quadrupoles. Each of the quadropoles focus the beam of ions in one transverse direction and defocus it in the other. The net effect on the beam after traveling through the system is focusing in all directions. Particle tracing of the ions is used to investigate the focusing effect of the quadropole.
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As the ions enter Q1, they start out evenly distributed around the larger circle, 3 cm from the z axis. Q1 focuses along the x axis and defocuses along the y axis. The force on each ion is approximately proportional to its distance from the z axis, so as the ions enter Q2, those that are far out on the x axis rapidly turn around and move towards the center. Q3 stabilizes the motion and gets all ions on the right track. Finally the ions are left to drift towards a waist situated a little bit more than 1 m beyond Q3. |
