Field free chamber in permanent magnet solenoids

摘要

A low-loss magnetic structure that provides an electron beam focusing field that can be accessed without field reversal. More specifically, the structure provides a uniform magnetic field that can be accessed from an adjacent field-free chamber within which an electron beam source of any size can be housed. The field-free chamber is separated from uniform field by a passive ferromagnet having a hole through which the electron beam can pass. The passive ferromagnet is instrumental in preventing the uniform field from entering the field-free chamber.