Magnetic lens to rotate transverse particle momenta

摘要

A magnetic rotator lens for rotating the momenta of particles transverse to the direction of the beam is disclosed. The rotator lens includes a solenoid axially aligned with the beam and employs a magnetic permeable flux return structure surrounding the solenoid. The flux return structure includes beam entrance and exit plates with magnetic permeable and charged particle permeable portions forming the beam entrance and exit ports of the magnetic lens. In a typical example, the beam entrance magnetic permeable and beam permeable portion of the pole piece structure is formed by a grid of magnetic permeable members. The magnetic permeable and beam permeable portions of the pole structures terminate the axial magnetic field without introducing any substantial transverse components to the magnetic field which would otherwise produce undesired rotation of the beam shape. The magnetic rotator lens is employed to advantage in a surface analyzer for focusing a ribbon shaped beam of photoelectrons through the entrance slit of a spherical electrostatic analyzer.