Multi-pole Deflector With Protrusions for Charged Particle Beam Imaging
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Solution Overview
Problem
Existing multi-pole deflectors for charged particle beams face challenges in achieving a compromise between structural simplicity and uniformity of the deflection field, particularly in the paraxial region next to the optical axis, due to distortions caused by the arrangement of poles and the number of feed ports, leading to aberrations and assembly complexities.
Innovation Solution
A multi-pole deflector design featuring at least two pairs of poles with circular arc-shaped sections and protrusions projecting inward from the radial side, arranged concentrically and diametrically opposite to each other, which minimizes off-axis aberration and enhances the uniformity of the resultant deflection field by compensating for the gradient of spacing between poles, thus simplifying the structure while maintaining accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the number of poles and feed ports is reduced to simplify structure, then device complexity is reduced, but field distribution uniformity deteriorates due to increased spacing gradients between poles
Solution Approach 1:
The patent applies local quality by providing protrusions at specific locations on the pole surfaces. These protrusions are strategically positioned to compensate for the spacing gradient between poles, creating localized field adjustments that improve overall field uniformity without requiring additional poles or feed ports. This localized modification allows the system to maintain simplicity while achieving better field distribution.
Solution Approach 2:
The patent changes the geometric parameters of the pole structure by adding protrusions with specific dimensions and positions. By adjusting the size, shape, and location of these protrusions, the system optimizes the electric field distribution to compensate for the reduced number of poles, thereby maintaining field uniformity with a simpler structure.
2Device complexity
If poles are arranged with larger spacing to simplify structure, then device complexity is reduced, but off-axis aberration increases due to field non-uniformity
Solution Approach 1:
The protrusions are positioned specifically on the pole surfaces facing the through-hole to locally enhance the field strength in regions where the spacing gradient causes field weakening. This localized field enhancement compensates for the off-axis field non-uniformity, reducing aberration without requiring complex pole arrangements.
Solution Approach 2:
The patent converts the harmful effect of spacing gradient into a beneficial arrangement by strategically placing protrusions that create localized field enhancements. These protrusions transform the field distribution pattern that would normally cause aberration into one that compensates for the gradient, thereby reducing off-axis aberration while maintaining simple pole spacing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design improves the uniformity of the deflection field within the through-hole, reduces off-axis aberration, and simplifies the manufacturing and assembly process, achieving a more efficient and accurate deflection of charged particle beams with a minimal number of poles and feed ports.
Implementation Method 1
Respective two poles in pairs of the at least two pairs of poles cooperate to generate respective secondary deflection fields distributed within the through-hole and across an internal space defined within the through-hole, respectively
Implementation Method 2
the deflector is a multi-pole electrostatic deflector, the at least two pairs of poles are at least two pairs of electrodes formed by a conductive material and configured to generate respective electric fields cooperatively when bias voltages are applied thereon respectively
Implementation Method 3
Respective two poles in pairs of the at least two pairs of poles cooperate to generate respective secondary deflection fields distributed within the through-hole and across an internal space defined within the through-hole, respectively
Implementation Method 4
the deflector is a multi-pole magnetic deflector, the at least two pairs of poles comprise at least two pairs of magnetic poles formed by a magnetic conductor material and having respective excitation coils which are attached onto respective radial sides of the at least two pairs of magnetic poles, and is configured to generate respective magnetic fields cooperatively when an excitation current flows through the excitation coils
Implementation Method 5
a reflector may for example be an electric deflector or a magnetic deflector, which deflects charged particles entering a deflection field generated by the deflector itself, depending on respective masses, moving directions, charges and the like of the charged particles
Data Source
AI summary
The invention provides a multi-pole deflector for a charged particle beam, and a charged particle beam imaging apparatus. The deflector includes a plurality of poles, including at least two pairs of poles, each pole in each pair of poles including a main body constructed in the form of a circular arc-shaped section and a protrusion projecting from an radial inner side of the main body. respective two main bodies of each pair of poles are arranged concentrically and diametrically opposite, and the at least two pairs of poles at least partially encompass and delimit a through-hole thereamong, which opens axially and is configured to receive and to pass therethrough the charged particle beam; and the at least two pairs of poles cooperate to generate respective secondary deflection fields distributed within the through-hole and across an internal space defined within the through-hole, respectively, and the secondary deflection fields are synthesized by combination of vectors into a resultant deflection field of the deflector which is distributed within and across the through-hole and is configured to deflect the charged particle beam passing therethrough.