This invention provides a charged particle source, which comprises an emitter and means for generating a magnetic field distribution. The magnetic field distribution is minimum, about zero, or preferred zero at the tip of the emitter, and along the optical axis is maximum away from the tip immediately. In a preferred embodiment, the magnetic field distribution is provided by dual magnetic lens which provides an anti-symmetric magnetic field at the tip, such that magnetic field at the tip is zero.

A magnetically microfocused electron emission source apparatus is disclosed. The apparatus may include a magnetic emitter unit, wherein the magnetic emitter unit comprises an emitter. Further, the magnetic emitter unit may include one or more magnetic portions formed from one or more magnetic materials, wherein the one or more magnetic portions of the magnetic emitter unit are configured to generate a magnetic field proximate to a tip of the emitter of the magnetic emitter unit for enhancing focusing of the emitted electrons from the electron emitter.

A magnetically microfocused electron emission source apparatus is disclosed. The apparatus may include a magnetic emitter unit, wherein the magnetic emitter unit comprises an emitter. Further, the magnetic emitter unit may include one or more magnetic portions formed from one or more magnetic materials, wherein the one or more magnetic portions of the magnetic emitter unit are configured to generate a magnetic field proximate to a tip of the emitter of the magnetic emitter unit for enhancing focusing of the emitted electrons from the electron emitter.

An electromagnetic compound lens may be configured to focus a charged particle beam. The compound lens may include an electrostatic lens provided on a secondary optical axis and a magnetic lens also provided on the secondary optical axis. The magnetic lens may include a permanent magnet. A charged particle optical system may include a beam separator configured to separate a plurality of beamlets of a primary charged particle beam generated by a source along a primary optical axis from secondary beams of secondary charged particles. The system may include a secondary imaging system configured to focus the secondary beams onto a detector along the secondary optical axis. The secondary imaging system may include the compound lens.

A fine-adjustable charged particle lens comprises a magnetic circuit assembly including permanent magnets and a yoke body, surrounding a beam passage extending along the longitudinal axis. The permanent magnet is arranged between an inner yoke component and an outer yoke component so as to form a magnetic circuit having at least two gaps, generating a magnetic field reaching inwards into the beam passage, into which a sleeve insert having electrostatic electrodes can be inserted, which may also generate an electric field spatially overlapping said magnetic field. In order to modify the magnetic flux and thus the magnetic field in the gaps, a thermal control element located in the yoke body introduces or extracts heat to or from components of the of the magnetic circuit assembly so as to thermally control or modulate the magnetic behavior of said components.

A fine-adjustable charged particle lens comprises a magnetic circuit assembly including permanent magnets and a yoke body, surrounding a beam passage extending along the longitudinal axis. The permanent magnet is arranged between an inner yoke component and an outer yoke component so as to form a magnetic circuit having at least two gaps, generating a magnetic field reaching inwards into the beam passage, into which a sleeve insert having electrostatic electrodes can be inserted, which may also generate an electric field spatially overlapping said magnetic field. In order to modify the magnetic flux and thus the magnetic field in the gaps, a thermal control element located in the yoke body introduces or extracts heat to or from components of the of the magnetic circuit assembly so as to thermally control or modulate the magnetic behavior of said components.

This invention provides a charged particle source, which comprises an emitter and means for generating a magnetic field distribution. The magnetic field distribution is minimum, about zero, or preferred zero at the tip of the emitter, and along the optical axis is maximum away from the tip immediately. In a preferred embodiment, the magnetic field distribution is provided by dual magnetic lens which provides an anti-symmetric magnetic field at the tip, such that magnetic field at the tip is zero.

This invention provides a charged particle source, which comprises an emitter and means for generating a magnetic field distribution. The magnetic field distribution is minimum, about zero, or preferred zero at the tip of the emitter, and along the optical axis is maximum away from the tip immediately. In a preferred embodiment, the magnetic field distribution is provided by dual magnetic lens which provides an anti-symmetric magnetic field at the tip, such that magnetic field at the tip is zero.

A magnetically microfocused electron emission source apparatus is disclosed. The apparatus may include a magnetic emitter unit, wherein the magnetic emitter unit comprises an emitter. Further, the magnetic emitter unit may include one or more magnetic portions formed from one or more magnetic materials, wherein the one or more magnetic portions of the magnetic emitter unit are configured to generate a magnetic field proximate to a tip of the emitter of the magnetic emitter unit for enhancing focusing of the emitted electrons from the electron emitter.

A magnetically microfocused electron emission source apparatus is disclosed. The apparatus may include a magnetic emitter unit, wherein the magnetic emitter unit comprises an emitter. Further, the magnetic emitter unit may include one or more magnetic portions formed from one or more magnetic materials, wherein the one or more magnetic portions of the magnetic emitter unit are configured to generate a magnetic field proximate to a tip of the emitter of the magnetic emitter unit for enhancing focusing of the emitted electrons from the electron emitter.